4. MANAGEMENT OBJECTIVES
The southern Australian shark fishery, apart from a range of broad goals that apply to a range of fisheries managed by the Australian Fisheries Management Authority, is currently managed for the following objectives.
Implement management arrangements to ensure that there is an 80% probability that in 2011, the mature biomass of the G. galeus stocks are above the 1996 level.
Maintain or rebuild each individual stock in the fishery to a level at, or above, 40% of the initial biomass.
Provide management arrangements which will encourage industry profitability and the best possible return from the resource.
The Southern Shark Fishery Management Advisory Committee (SharkMAC) advises the AFMA Board on the management of the fishery. SharkMAC comprises an independent Chairman, five industry members, a State Government member, a research member, a member who represents the conservation interests the public and an AFMA member. SharkMAC has several subcommittees. The Shark Industry Research Liaison Committee (SIRLC) sets research priorities for the fishery and evaluates applications for funding from various research funds. The Southern Shark Fishery Assessment Group (SharkFAG), which works closely with SIRLC, undertakes and reviews stock assessments and economic assessments of the fishery and recommends further research required to improve assessments; and resolve uncertainties. Both SIRLC and SharkFAG are comprised of scientists, shark industry members and the AFMA Manager of the Southern Shark Fishery. To provide for equitable quota management, an Allocation Advisory Panel will be established to provide advice to the AFMA, Board on the most appropriate allocation process for the fishery (Walker et al. 1997b).
In New Zealand the national policy is to manage fisheries under the Quota Management System. The policy also encompasses the management of recreational fisheries and provision for customary Maori fishing, including Mataitai reserves. The Ministry of Fisheries is advocating ecosystem management as the underlying principle of the proposed Fisheries 2010 Strategy. Broad goals stated to cover all fisheries include G. galeus; there are no specific objectives stated for this species. The management objective for all New Zealand fisheries, as stated in the Fisheries Act 1996, is to manage them in a way that will lead to production of the Maximum Sustainable Yield (Francis and Shallard 1999).
The US has a shark fishery management plan for the east coast but not for the west coast, hence there are no stated objectives for sharks which cover G. galeus (Rose 1998). Similarly, there are no stated objectives for the G. galeus fisheries operating off the east coast of South America or South Africa.
For the North East Atlantic, the principal policy objectives of the EC Common Fisheries Policy are to protect fish stocks in EC waters from overfishing, guarantee fishers a future livelihood and ensure that the processing industry and consumers enjoy regular supplies of fish at reasonable prices (Fleming and Papageorgiou 1996).
5. MANAGEMENT POLICIES AND THE POLICY SETTING PROCESS
5.1 Policies adopted
5.1.1 Resource access
In southern Australia, apart from the requirement for vessels to be registered as fishing vessels by the Commonwealth and State fisheries agencies, and the prohibition on the use of shark fishing gear in some areas, the Southern Shark Fishery was an open access fishery until 1984. Since then an endorsement allowed an operator to use a vessel to take shark with gill-nets of mesh-size exceeding 150mm in Commonwealth waters. More recently special Shark Fishing Permits to use longlines apply (Walker et al. 1997b).
5.1.2 Gear restrictions
In southern Australia, during 1988, the use of gill nets in the prescribed area of the southern Australian shark fishery was controlled by the Southern Shark Fishery Management Plan established under the Fisheries Act 1952 (replaced by the Fisheries Management Act 1991). This management plan reduced the effort by controlling the number, size and construction of gill nets, and the number of operators permitted to use them. The management plan created a unit of gill-net fishing capacity, called a ‘net unit’. Each net unit permitted the use of a standard gill-net defined as a monofilament gill-net with a head-line length of 600m, 20 meshes deep with mesh-size > 150mm. Mesh-size was defined as the distance between opposite knots of the mesh diamond when pulled taut. The depth of a gill-net could be >20 meshes provided there was a corresponding decrease in its head-line length and approval to make the alteration by the manager of the fishery (i.e. overall area of the gill-net had to be the same). Based on a vessel's catch history during a 5-year qualifying period, each shark gill-net endorsement was classed as either a Category A endorsement or a Category B endorsement. A vessel with a Category A endorsement received 6 net units, a Category B endorsement received either 5, 4, 3 or 2 net units depending on the number of gill-nets used during the qualifying period. These were referred to as B5, B4, B3 and B2 endorsements, respectively, and many of the operators with these endorsements were licensed to operate in other fisheries.
A total of 241 endorsements and 1234 net units were initially issued. An annual levy was charged for each unit. These units were nontransferable outside immediate family members. Non-transferability of shark gill-net endorsements, in conjunction with the policy enforced by the Commonwealth and State fisheries agencies of prohibiting the splitting of licence packages, markedly reduced the number endorsements and net units in the fishery. To reduce the number of vessels engaged in the fishery full-time, the management plan allowed for amalgamation of two A6 endorsements to provide for an A10 endorsement with 10 net units. An amalgamation involved the forfeiture of 2 of the 6 net units attached to the A6 endorsement on one licence and the transfer of the remaining 4 net units to a second licence which then had its A6 endorsement converted to an A10 endorsement. The amalgamation process, which ended on 30 May 1990, created 40 separate A10 endorsements and removed 40 vessels and 80 net units from the fishery. The requirement for endorsement holders to pay levies also contributed to a decline in the number of vessels and gill-net units in the fishery as it became less economic to continue in the fishery at a low level. This levy was based on the number of net units and was collected to meet management costs. At present there is a total of 125 vessels with net units in the fishery. Of these, 40 vessels have A10 endorsements, 28 have A6 endorsements and 57 have Category B endorsements. Interim net reductions of 30% for A10 endorsements, 33% for A6 endorsements, 40% for B5 endorsements and 25% for B4 endorsements were implemented during April 1991. B3 and B2 endorsements were not altered. This reduced the number of net units in the fishery by about 33% overall. Later, in April 1993, the number of net units were restored and a uniform 30% reduction on all shark endorsements was applied by reducing the standard net length per net unit from 600m to 420m.
Entry criteria and management arrangements were adopted for vessels using longlines after 1 January 1994. By 1 July 1995, 31 applicants had been granted Shark Hook Permits to use either 2000 or 1000 hooks depending on their catch history. By June 1996 this had increased to 35 permits. A legal minimum gill-net mesh-size of 150mm was first adopted in 1975 and remains current. This is designed to complement the legal minimum lengths. A maximum mesh-size for the fishery of 165mm took effect from 1 January 1997. This is designed to discourage fishers targeting pregnant and other mature G. galeus (Walker el al. 1997b).
In New Zealand, minimum mesh-sizes of 125mm and 150mm apply for G. galeus in northern New Zealand and southern New Zealand, respectively. Numerous general restrictions apply to the use of commercial and recreational gill-nets and longlines, including limits on the length of gill-nets, number of hooks per longline, number of longlines, soak time, the amount of an estuary or bay that can be blocked by a gill-net and areas that can be fished. The restrictions vary regionally and are designed to reduce the number of nets lost and the amount of fish wasted to sea lice and decay because of excessively long sets, and to minimise conflict with other users of inshore waters. Also, G. galeus is covered by the mixed species daily bag limits for recreational fishers of 20 and 30 fish for the northern and central regions and southern region of New Zealand, respectively (Francis and Shallard 1999).
In California, gill-nets are prohibited in State waters. Gear regulations do not apply specifically to G. galeus in the other regions.
5.1.3 Vessel regulations
The southern Australian fishery has no vessel regulations other than requiring all vessels to pass a maritime survey (Walker et al. 1997b). Similarly New Zealand has not adopted vessel regulations as a means of managing shark fisheries (Francis and Shallard 1999). Argentina and Uruguay require industrial vessels to operate outside prescribed distances from shore, and their artisanal vessels to operate inside limited distances from shore or home port. Brazil also has a coastal exclusion zone for large industrial vessels. South Africa closes some areas to certain vessels.
5.1.4 Biological regulations
5.1.4.1 Southern Australia
In southern Australia, a number of biological regulations, proclaimed under Commonwealth law or State law, or both, are either currently in place, or have been adopted and subsequently abandoned. These regulations include legal minimum lengths, a legal maximum length, legal minimum and maximum mesh-sizes of gill-nets, closed seasons and closed areas.
Legal minimum lengths were phased in by the States and Commonwealth during 1949 and the early 1950s and remain current. The legal minimum length for G. galeus was 91 cm TL throughout the range of the fishery. Because sharks are landed headed and gutted, during 1975–77 the lengths were revised to a partial length (fifth gill-slit to base of caudal fin) of 40cm (equivalent to 71 cm TL).
A legal maximum length on G. galeus marketed in Victoria, designed to reduce the average concentration of mercury in the catch, applied during 1972–85. Initially this length was 104cm total but was revised during 1976 to 63cm partial length (equivalent to 112cm TL). The legal maximum length was abandoned in June 1985 following revision of the Australian food standard for mercury in fish.
Fishing seasons during October or November were closed during 1953–67, the months prior to when they give birth, to protect pregnant female G. galeus. More recently, in 1993 and 1994, seasonal restrictions were imposed to provide some protection to pregnant females migrating to nursery areas. Areas closed to commercial gill-netting in inshore waters of Tasmania have been variously implemented since 1954 to protect newborn and juvenile G. galeus in nursery areas. A more extensive closed area was adopted in 1988 when all Victorian proclaimed waters (inside 3-mile limit) were closed to the use of shark gill-nets and longlines. There are several marine parks and reserves in southern Australia where shark fishing is prohibited. Most of these are in State proclaimed waters.
5.1.4.2 Other regions
Apart from restricted areas for certain classes of vessels and a prohibition on the use of gill-nets within 3nm of the coast of California, specific biological controls do not apply in other regions.
5.1.5 Catch quota allocation
The southern Australian fishery has been managed through input controls. The Australian Fisheries Management Authority's preferred method of management is through output controls and following a review of management options for the fishery set early 1999 as the goal for implementation of Individual Transferable Quota management. However, the shark fishing industry requested a number of preconditions be met before its adoption. Catch limits on shark bycatch have been imposed in some other fisheries. For example fishers granted Commonwealth Fishing Permits to target scale fish in Commonwealth waters with hooks are limited to a bycatch limit of five G. galeus and Mustelus antarcticus. In Victorian coastal waters (outside State internal waters) all commercial fishing licences are limited to a catch of 50kg (carcass weight) of G. galeus and M. antarcticus. In New Zealand a Quota Management System was introduced during October 1986. The Total Allowable Commercial Catch was initially set at 2590t but this was revised to 3106t by 1995–96. Landings have usually been below these set levels. Catch quotas do not apply to the G. galeus fisheries in the other parts of the world.
6. THE MANAGEMENT PLANNING PROCESS
6.1 Biological management reference points
In southern Australia, discussions about 5 years ago considered that the biomass of each of the major species in the fishery should not fall below 40% of initial biomass. It was considered that this should provide an adequate safety margin for shark species which tend to have lower fecundity than teleosts and invertebrates. More recently, as a result of dialogue between research and management bodies when revising and improving the G. galeus assessment, risk has been expressed in terms of the probability of the mature biomass being below current biomass levels in 15 years time in the future under alternative harvest strategies (Walker et al. 1997b).
In New Zealand, the Fisheries Act (1996) requires that fisheries be managed to produce Maximum Sustainable Yield (MSY). The MSY is estimated in terms of the Maximum Constant Yield (MCY) or the Current Annual Yield (CAY). MCY is the ‘maximum constant catch that is estimated to be sustainable, with an acceptable level of risk at all probable future levels of biomass’. CAY is the ‘one-year catch calculated by applying a reference fishing mortality, Fref, to an estimate of the fishable biomass present during the next fishing year. Fref is the level of instantaneous fishing mortality that, if applied every year, would, within an acceptable level of risk, maximise the average catch from the fishery’. MCY is a constant catch strategy, whereas CAY is a constant fishing mortality strategy. CAY varies annually in response to fluctuations in population biomass (Annala and Sullivan 1997; Francis and Shallard 1999). CAY cannot be estimated for G. galeus in New Zealand but MCY estimates have been made using the equation
MCY = cYav
where Yav is the average yield (landings) and c is a natural variability factor estimated from the natural mortality rate that allows for anticipated fluctuations in biomass. c is inversely related to the natural mortality rate. Because the natural mortality rate of G. galeus is low, the c value is relatively high (Annala and Sullivan 1997; Francis and Shallard 1999).
Biological management reference points have not been prescribed for the other G. galeus fisheries.
6.2 Stock assessment
Stock assessment of G. galeus has only been undertaken in southern Australia and New Zealand. The Australian assessments are based on models incorporating demographic parameters, fishing gear selectivity parameters and time series data of catch and CPUE whereas the New Zealand assessments are based on fishery-independent demersal trawl survey data. The geographic ranges of most of the world's G. galeus fisheries overlap demersal trawl fisheries and regular trawl surveys are undertaken in New Zealand (Annala and Sullivan 1997), South Africa (Compagno et al. 1991), Argentina (Cousseau 1986), Uruguay (Ehrhardt et al. 1977a, b), and southern Brazil (Peres and Vooren 1991). They are not undertaken in Australia. The surveys that have been undertaken cover all or most of the important species of fish, and, although all these surveys have data for G. galeus and other species of shark, only New Zealand has attempted to use the data to estimate biomass.
The results from trawl surveys in New Zealand undertaken during the mid-1980s, sometimes from a variety of different vessels, were used to provide an approximate estimate of minimum absolute biomass. This required an assumption about catchability to convert trawl survey catches to estimates of absolute biomass. Areal availability and vertical availability of G. galeus were set equal to 1.0, and vulnerability was usually set equal to the ratio of the door-spread biomass estimate divided by the average of the wingspread and the door-spread biomass estimates (i.e. usually about 0.4). The Maximum Constant Yield was estimated at 1840t from the equation MCY = cYav.
The Total Allowable Commercial Catch for G. galeus was set at half the 1983 catch because of apparently declining catch rates and concern about the undoubtedly low productivity of the species. It is not known if the Total Allowable Commercial Catches are sustainable, or will allow the stocks to move towards a size that will support the Maximum Sustainable Yield (Annala and Sullivan 1997).
In southern Australia, Olsen (1954) drew attention to the slow growth rate and low reproductive capacity of G. galeus and stressed the need to safeguard the recruitment processes of the stock by (a) protecting pregnant sharks during the 2-months prior to birth, (b) declaring known ‘pupping’ areas as sanctuaries for young sharks and (c) adopting a legal minimum length. Olsen (1959) argued that the life history characteristics of G. galeus makes it vulnerable to the effects of heavy fishing and drew attention to the collapse of the Californian fishery for this species during the 1940s which at the time was believed to be closely related to the G. galeus of southern Australia (and is now considered to be the same species). Olsen (1959) further argued that the southern Australian stock of G. galeus should be compared with marine mammals, such as whales and seals, rather than the stocks of the more fecund and faster growing teleosts and invertebrate species. While Olsen (1959) was careful to note that the data for G. galeus do not show that the southern Australian population was depleted, he believed there was sufficient evidence to ‘discuss measures to conserve the stocks in order to maintain a maximum steady yield’. He presented evidence of a decline in abundance of juvenile sharks in the inshore waters of Port Phillip Bay in Victoria during 1943–54 and in the Pittwater and Port Sorell estuaries of Tasmania during 1948–52. He also showed a decrease in catch per hook, a decrease in the mean weight of sharks landed, an increase in the amount of gear carried by each fishing boat, and the change from an inshore to an offshore fishery involving increases in distances travelled from port.
During the late 1960s and early 1970s, a series of four quantitative assessments (Kesteven 1966; Walker 1970; Harrison 1970; Grant et al. 1979) based on CSIRO tagging data (Olsen 1953, 1954) were undertaken. Apart from the analysis by Harrison (1970) which included reproduction parameters of G. galeus, these early assessments were based on a Beverton and Holt yield per recruit analysis. All four of these assessments suggested that the G. galeus resource was sound. In the early-1970s fishers complained that the stocks appeared to be declining. However, the ban on the sale of large G. galeus in Victoria during 1972–85, and the switch in targeting from G. galeus to Muslelus antarcticus coinciding with the switch from the predominant use of longlines to the predominant use of gill-nets in Bass Strait alleviated much of the concern for the stock status of G. galeus. At that time much of the interest in stock assessment switched from G. galeus to M. antarcticus, but many of the innovations adopted for assessing the M. antarclicus stocks were subsequently adopted for G. galeus.
Earlier assessments had been free of the complexities of gill-net selectivity because until the early 1970s most sharks were caught by hooks. with hooks, sharks longer than the legal minimum length are equally vulnerable to capture but, in gill-nets, sharks of different size are not equally vulnerable. Small sharks swim through gill-nets but become progressively more vulnerable to capture as they grow. After reaching the length of maximum vulnerability sharks then become progressively less vulnerable as they tend to be deflected from the nets because their heads cannot so readily penetrate the meshes (Kirkwood and Walker 1986).
During 1983–91 the assessments focused on M. antarcticus but later G. galeus received equal attention. Through this period, other difficulties identified with the stock assessments included the use of CPUE as an index of relative abundance, the movement patterns of the sharks and the effects of using fixed growth, fecundity and natural mortality parameters values. The early workshops considered that many of the underlying assumptions of various models applied to M. antarcticus and G. galeus were invalid (Walker 1986). For more rigorous assessments of the southern shark stocks, it became clear that special models had to be developed for this fishery.
Walker (1986) developed an age-structured model which was applied to M. antarcticus to incorporate the length-selective characteristics of gill-nets and, following Holden (1974), the peculiarities of the shark reproduction. Initially the model assumed the stock was in equilibrium and contained no density-dependent regulation. Density-dependent regulation was subsequently incorporated into the model by assuming natural mortality of various juvenile age-classes varied with biomass or stock number in selected age-classes (Prince 1991; Walker 1991, 1992) or all age-classes (Walker 1994a,b). At this stage a computer graphics package ‘Sharksim’ was developed for simulating the fishery (Sluczanowski 1991; Sluczanowski et al. 1993).
Using a general computer software framework initially programmed by C.J. Walters (University of British Columbia) and subsequently adapted by N. Hall (Western Australian Marine Research Laboratories) for sharks, Prince (1991) used a range of assumed parameter values for catchability and natural mortality to estimate changes in biomass and future catches for various fishing effort management scenarios. Initial assessments assuming either single stocks or multiple stocks of G. galeus with these models indicated that the stocks were depleted.
In 1993 a new group known as the Southern Shark Fishery Assessment Group (SharkFAG) was formed. This is a sub-committee of the Southern Shark Fishery Management Advisory Committee (SharkMAC). The group consists of biologists, modellers, fishers, fishery managers and economists. An important element of SharkFAG meetings has been the active participation of industry members with their practical fishing experience. They have provided valuable insights into targeting practices, fish movement, stock structure and the validity of the assumptions used in the analyses.
SharkFAG applied several modelling approaches during 1994 and 1995 as part of its first assessment of G. galeus. Two types of model (standard biomass dynamics models and delay-difference models) were considered during that assessment. Both types of model used catch and CPUE data and were applied assuming a single stock of G. galeus. The delay difference-model also made use of information on growth, natural mortality and data on the mean individual weights of captured G. galeus.
The assessment concentrated on ‘standardising’ the CPUE data to remove the effects of different gear types and regions in the fishery. The raw catch and effort data were standardised using a generalised linear modelling approach based on the assumption that the errors were independent and identically distributed according to a log-gamma distribution (Xiao 1995a). The model included factors for year (1973 – 93), zone (Tasmania, Bass Strait, South Australia, and Western Australia), and gear-type (hooks, and 6-, 7- and 8-inch mesh-size). Including gear-type as a factor in the analysis was questionable, however, as different gear-types target different components of the population. The analysis suggested that the standardised CPUE had been roughly stable from 1982 to 1993.
Xiao (1995b) undertook an assessment of G. galeus using the Schaefer biomass dynamics model. Analyses with this model were undertaken for a range of fixed values for an intrinsic rate of growth from 0.01 to 0.lyr-1. Each analysis involved estimating values for the catchability coefficient and the virgin biomass (assumed to be the same as the biomass at the start of 1930). A risk analysis was based on the results of a bootstrap assessment. The assessment suggested that the biomass had dropped to 50% of virgin biomass by 1973 and a further 50% subsequently. The risk analysis suggests that the 1993 catch was unsustainable and that catches should be reduced.
Walker (1995b) based an assessment on the delay-difference model (Deriso 1980; Schnute 1985, 1987). The model of Xiao (1995b) used catch data for 1930-93 and CPUE data for 1973–93 standardised by Xiao (1995a). Natural mortality and growth were fixed based on auxiliary data and only catchability and the parameters of the stock-recruitment relationship were estimated. Although this model incorporated the biological processes of natural mortality and growth, it had to assume that selectivity was ‘knife-edged’. This may be inappropriate given that gill-nets are known to be highly size-selective. The assessment and a risk analysis indicated that the stock was 15–25% of its 1930 size, that recruitment was stable, and that the stock would stabilise with the 1990 level of effort. The stock was predicted to rebuild to 30–40% of its 1930 level if fishing mortality was halved.
A variant of the model developed for M. antarcticus that allowed for age-specific natural mortality (Walker 1994b) was applied to G. galeus. The population was divided in two (eastern and western) components all births were assumed to occur in the eastern region. Work on this model ceased when SharkFAG began developing a fully age- and spatially-structured model that uses spatially disaggregated data for G. galeus.
An important uncertainty in the assessment was how ‘targeted effort’ for M. antarcticus and G. galeus was defined. Another uncertainty lay in the lack of understanding of the recruitment process which cannot be adequately determined from the models. Current low catch rates of juvenile sharks in nursery areas compared with those during the 1940s, alteration of the habitat of sharks and the incidental mortality of juvenile sharks from other types of fishing all contribute to uncertainty about the recruitment process. However, examination of size-composition data for the last 20 years suggested that recruitment had been stable over that period. In addition, the data collected by the current nursery study over the last 4 years shows low, but consistent, pup abundance.
Deficiencies of the Schaefer production and delay-difference models adopted for the 1995 assessment G. galeus assessment led SharkFAG to favour age-structured models. The view is that the soundest approach to G. galeus stock assessment is to adopt fully age-structured models that incorporate the peculiarities of shark biology, the selectivity of the fishing gear, the movement patterns of the sharks and the use of spatially-disaggregated data.
Details of model structure, parameter values and risk analyses are given in Punt and Walker (1998). Key findings of the 1996 assessment are as follows:
The median of the posterior for the size of the mature biomass of the G. galeus resource at the start of 1995 is estimated to lie between 15% and 46% of the unfished level.
Despite the uncertainty in these biomass estimates, catches have been substantially larger than the estimates of MSY.
There is a high probability that current effort will lead to further reductions in population size. To achieve the objective that there be an 80% probability that mature biomass is above the 1996 level of mature biomass in 15 years time, a catch reduction of about 35% is required.
It is possible to phase-in the required reductions, however this will result in a lower long-term sustainable catch.
One major uncertainty in the assessment is spatial structure of the population. The issue of single versus regional stocks is complicated and cannot be resolved in the short-term. Current genetics and tagging studies are addressing this uncertainty.
The 1996 assessment for G. galeus examined alternative hypotheses and SharkFAG identified several factors which could substantially affect the results. Some of these have been identified because SharkFAG has attempted to examine a broader range of modelling hypotheses than is commonly the case. The results are highly sensitive to the selection the method used to standardize the catch and effort data. In particular, the results depend markedly on whether a log-normal or Poisson error-structure for standardisation of CPUE is used, and how zero catches are handled (Punt et al. 1996). None of the analyses conducted currently permit discrimination among the options, so these are considered to be equally likely. Another factor which may affect the results are assumptions about shark movement. Several distinct types of shark movement have been identified: (a) vertical movement, which possibly results in a substantial fraction of the population being unavailable to the fishing gear at any one time, (b) movement between close inshore and offshore, (c) movement to and from New Zealand, and (d) movement within the fishery itself. These issues can only be dealt with using a fully spatially-structured population dynamics model for the fishery.
The majority of the model predictions are based on the assumption that fishers who use 7-inch and 8-inch mesh-size changed to 61/2-inch mesh-size from 1 January 1997. This has been implemented by assuming that these fishers will continue to target the way they did in the past. This assumption seems to be the ‘best’ possible at present but will fail to some extent because of the differences among the various regions within the fishery.
The results of the stock assessment are highly imprecise if no constraints are placed on the parameter which determines the productivity of the resource, MSYR1. This is a consequence of the uninformative nature of the catch and effort data for this species. The alternative probabilities assigned to different values of MSYR reflect a consensus within the assessment group based on estimates for other shark species and intuitive judgements. These probabilities are the best currently possible, but may be substantially in error. Information is lacking about productivity for most shark species, so making inferences about likely ranges in MSYR for G. galeus is difficult.
The assessment group attempted to specify the full range of plausible modelling hypotheses. Although the hypotheses specified cover a wide spectrum, there are probably several hypotheses which were not identified but are nevertheless plausible. Some of these hypotheses (e.g. the degradation of some historical pupping grounds) could have a substantial impact on long-term population projections.
6.3 Discussion
The life history traits of sharks differ from those of most teleosts and invertebrates and are more like those of marine and terrestrial mammals, i.e. K-selected animals. Hence, in many ways, the dynamics of shark fishery stocks have more in common with marine mammal populations than they do with teleost or invertebrate fisheries. Thus, the application of fishery assessment models must be applied with care.
In the absence of time series of catches and stock abundance indices, shark populations are assessed using either demographic analysis or yield-per-recruit analysis which ignore density-dependent regulation. Demographic analysis is the process by which age-specific mortality and natality rates are combined to produce estimates of the net reproductive rate, inter-generation period, and intrinsic (instantaneous) rate of increase. This involves the construction of a cohort or static life table for the population, based on reliable estimates of mortality, natality, and longevity and usually assumes a stable age distribution, equal sex ratios, and a constant recruitment rate. The method of demographic analysis was recently extended to incorporate density-dependent effects by allowing adult mortality to change with population size. Yield-per-recruit analysis is a simpler form of demographic analysis because it does not include reproductive rates; like demographic analysis it assumes recruitment is constant and independent of stock size.
Stock assessments should incorporate a time-series of total catch estimates in numbers or weight because these represent removal of biomass and individuals from the ecosystem and are the fundamental impact fishing has on the populations. The assessments should also incorporate a time-series of abundance indices based on CPUE or fishery-independent surveys. Where time-series of catches and stock abundance indices are available, shark populations can be assessed using biomass dynamics models. These models make the assumptions that the rate of population increase responds immediately to changes in population density and that the rate of natural increase at a given density is independent of the age composition of the stock. Whilst these assumptions might be reasonable for the short-lived more highly productive species, they are most likely invalid for long-lived species of low productivity.
Delay-difference models have advantages over biomass dynamics models in that they can incorporate some biological information. However, neither biomass dynamics nor delay-difference models can incorporate all information on shark reproduction, and both assume ‘knife-edge selection’ which is not a valid assumption in gill-net or trawl fisheries.
The most appropriate assessment models for sharks are fully age-structured non-equilibrium models that can include time-series of catch and abundance indices, the demographic parameters for growth, reproduction and natural mortality, and fishing gear selectivity parameters. These models can be adapted to incorporate ancillary data such as mean size or mean weight of shark in the catch. They can also be readily adapted to incorporate alternative assumptions on density-dependent mechanisms operating through density-dependent natural mortality, fecundity or growth. These models can also be spatially structured to use spatially disaggregated data and to allow for movement of sharks between different regions of the fishery.
7. FISHERY MANAGEMENT REGULATIONS
7.1 Southern Australia
Responsibility for management of the shark fishery is currently shared by the Commonwealth Government and the State Governments of Victoria, Tasmania and South Australia, but steps are being taken to bring the fishery under a single jurisdiction (i.e. Commonwealth jurisdiction with the exception of 'State internal waters' which will remain under State jurisdiction). State jurisdiction extends 3nm from the coastline and Commonwealth jurisdiction extends from the 3-mile limit to the 200nm limit of the Australian Fishing Zone.
These arrangements have meant that in the past the fishery has been regulated and continues to be regulated under the jurisdictions of the Commonwealth and the three States. Hence current arrangements for vessel registration, fisher licences, special limited entry licences/permits, fishery regulations and the taking of sharks, or use of shark fishing gear under research permit, are extremely complex. Commonwealth regulations are proclaimed and licences/permits are administered under the Commonwealth Fisheries Management Act 1991 while State regulations are proclaimed and licences are administered under the State fisheries Acts of Victoria, Tasmania and South Australia.
To simplify management arrangements the Commonwealth and State Ministers responsible for fisheries in Victoria, Tasmania and South Australia have agreed to place the majority of the fishery under a single jurisdiction. This can be achieved under the Commonwealth Fisheries Amendment Act 1980 which is part of a parcel of 14 Acts termed the Offshore Constitutional Settlement (OCS) and enacted on 14 February 1983. This makes provision for managing fisheries under joint authorities of the Commonwealth and one or more States, or by the Commonwealth only, or by one State only (Anon 1989). The Fisheries Ministers have agreed that the fishery be managed under Commonwealth law. Resolution of these jurisdictional arrangements will be incorporated into an Offshore Constitutional Settlement agreement and a Memorandum of Understanding between the Commonwealth and States that is close to finalisation.
State Internal Waters will continue to be managed by the States. These are waters that fall inside the baselines defining the inner edges of the States' 3-mile limits. The baselines run from point to point, enclosing considerable bodies of water where coastlines are highly indented or where there are islands or rock outcrops. Substantial areas of internal State proclaimed waters occur adjacent to the SSF and include Spencer Gulf and Gulf of St Vincent in South Australia and areas of Bass Strait around Tasmanian islands and most of the inshore and estuarine areas around south-eastern Tasmania. The bays and inlets of Victoria all form internal waters but the main ones where G. galeus and M. antarcticus occur are Port Phillip Bay, Western Port and Corner Inlet. The State fisheries agencies and AFMA have agreed to apply complementary management arrangements in the areas under their jurisdictions.
A number of biological regulations are either currently in place, or have been adopted, and subsequently abandoned. These regulations include legal minimum lengths, legal maximum lengths, legal minimum and maximum mesh-sizes of gill-nets, closed seasons and closed areas.
Gazetting of proclamation, rescission or amendment of regulations in Government Public Notices is standard practice by the Commonwealth and State fisheries agencies involved in management of the SSF. These agencies also publish these changes in their periodical magazines and often advise licence holders directly in writing. The flow of information is also facilitated by the presence of fisheries enforcement officers based in regional offices (Walker et al. 1997b).
7.2 New Zealand
In New Zealand, G. galeus is currently managed under the Quota Management System by the Ministry of Fisheries. It is included in the daily mixed species bag limit for recreational fisheries and fishing for this species is subject to the general restrictions on areas fished, gill-net mesh-sizes and the amount of gill-net and longline that can be deployed by commercial and recreational fishers. There are no closed seasons or shark size limits (Francis 1998).
7.3 North East Atlantic
The 200-mile EEZ of the coastal member nations of the EC was declared in 1977 and the EC Common Fisheries Policy which sets our common rules applicable to EC member countries, was established in 1982, reviewed during the early 1990s and ratified in 1992. The CFP recognises that coastal states have exclusive access to, and authority to manage fisheries within their territorial waters, i.e. to the 12nm limit. Within 6– 2nm, other EC member states may have historic access rights to certain fisheries.
Outside the Mediterranean, rules to protect fisheries resources from overfishing are based on information provided by the EC's Scientific, Technical and Economic Committee for Fisheries (STECF) and by ICES. Each year these bodies assess various fish stocks in each of the ICES fish stock areas and recommend TACs for selected species which are divided into National Quotas. Fisheries for a particular stock must be closed once a TAC or National Quota has been reached. TACs have never been set for G. galeus or any other chondrichthyan species.
In the Mediterranean, the EC Common Fisheries Policy has limited application because only four countries-Greece, Italy, Spain and France-are EC member states. Most fisheries management agreements are made through the General Fisheries Council for the Mediterranean (Fleming and Papageorgiou 1996).
7.4 Other regions
In South Africa, special permits are required for shark longlining, which are restricted to 31 permits, and hand-lining, which are not restricted by number (Kroese et al. 1995). Otherwise no regulations exist specifically for G. galeus. In the Northeast Pacific, G. galeus is managed by the Pacific Marine Fishery Council. In California, there are no fishing regulations directed at this species other than those imposed on all gill-nets (Holts 1988). In all regions, general regulations probably affect the bycatch of G. galeus in many fisheries, otherwise there are no, or few regulations, established specifically for G. galeus.
8. THE LAW AND ENFORCEMENT
8.1 Southern Australia
The shark fishery currently has no major enforcement problems. Most at-sea and on-shore surveillance has been undertaken by the States which have regional and in-port offices for surveillance and extension purposes. Enforcement of licensing provisions, gear restrictions, mesh-size, closed season and legal lengths can be undertaken on-shore, and the need for costly at-sea surveillance is limited. The Australian Fisheries Management Authority can undertake satellite surveillance through a Vessel Management System which can be used for monitoring positions and times of vessels at sea. So far this system for the enforcement of closed areas or, historically, closed seasons, has not been considered necessary for the fishery. Systems for quota management have been established by Australian Fisheries Management Authority and the States for other fisheries. However, it is currently considered impractical to implement quota management in the SSF until the fishery is managed under a single jurisdiction.
The Australian Commonwealth and States have Legal Officers and Enforcement Officers with authority to apprehend and prosecute offenders. A fisheries agency (or police department) can initiate legal proceeding through the courts. Some agencies can issue on-the-spot fines for minor offences which avoids the need for court appearances unless the accused chooses to challenge the fine. Most penalties include fines or licence suspension but repeated offences can result in imprisonment. Right to appeal exists against licence cancellation or restriction of licence conditions through the Australian Administrative Appeals Tribunal in the case of Commonwealth licences/permits or a Licence Appeals Tribunal in the case of State licences/permits but must be exercised within a limited period. Appeals can also be lodged through the courts (Walker et al. 1997b).
8.2 New Zealand
The powers to manage and enforce the Total Allowable Commercial Catches and other regulations are provided under the New Zealand Fisheries Act 1996. Where catches are taken in excess of quota holdings the permit holder may purchase further quota, lease further quota, or land catches against the quota holding of another lease holder. Furthermore, in any year, a quota holder can carry forward quota to the next year, providing it is <10% of the holding for a particular Fishstock. Conversely, a quota holder may take catches up to 10% more than the quota holding, but the additional amount of catch is deducted from the subsequent year's catch entitlement.
Fisheries surveillance, investigation and prosecution of offences in New Zealand is done by Fishery Officers employed by the Ministry of Fisheries. Surveillance is undertaken by means of random supervision of landing points, catch record monitoring, and inspections and audits of Licensed Fish Receivers. The legal basis for enforcement of fisheries regulations is provided in the Fisheries Act, which defines the offences and penalties for convicted persons. The Ministry of Fisheries must investigate alleged offences and bring prosecutions before the courts. The penalty for all offences under current law is a monetary fine, but there are provisions for forfeiture of catch, fishing gear, fishing vessel, and ITQ on conviction for a range of offences prescribed by in the Fisheries Act 1996 (Francis and Shallard 1999).
8.3 Other fisheries
In the Northeast Atlantic, responsibility for enforcing the regulations of the Common Fisheries Policy of the EC rests with the fisheries officers of the EC member states (Fleming and Papageorgiou 1996). Similarly, in other G. galeus fisheries responsibility for enforcement of regulations rests with the separate countries, or within-country states. Only Argentina and Uruguay share regional management - for their Area Comun de Pesca. There are minimal enforcement problems relating to G. galeus in these countries, or within-country states because there are only a few relevant regulations to enforce. Argentina, Uruguay, Brazil and South Africa have separate inshore zones for the artisanal fleets and offshore zones for the industrial fleets which are sometimes contravened.
9. MANAGEMENT SUCCESS
In southern Australia, halving the number of vessels operating in the shark fishery in Commonwealth waters and reducing fishing effort by about one-third over the last decade has provided some improvement in the efficiency of the fishery. However, whilst the M. antarcticus catch increased marginally much of the economic gain from reduced effort has been offset by a large reduction in the G. galeus catch. Nevertheless, most operators dependent on shark operate profitability and benefit from the management changes. The current method of management with input controls does raise issues of equity and efficiency. The legacy of the original gear allocation processes based on historical levels of catches and amount of fishing gear used during the qualifying periods has resulted in large differences in gear entitlements by current operators. At present, the holder of a Commonwealth Shark Fishing Permit has no facility to upgrade the gear entitlements or transfer the gear entitlements to another operator. Implementation of ITQ management will address the problem of inefficiency, but the process of allocation of quota will inevitably raise issues of equity (Walker et al. 1997b).
In New Zealand, there is extensive involvement of stakeholders in the annual process of stock assessment, setting of Total Allowable Commercial Catch, cost recovery and canvassing on views and positions of the Ministry of Fisheries, research providers, commercial and recreational fishing interests, and Maori interests (Francis and Shallard 1999).
In the North East Atlantic, TACs have been applied to ~15% of fish caught or landed by EC countries, but an EC TAC or EC National Quota has not been set for any shark species. However Norway and the Faeroe Islands have fishing agreements with certain other EC countries to take quotas of basking (Cetorhinus maximus) and porbeagle sharks (Lamna nasus). No direct measures to regulate G. galeus, or any other species of shark, have been applied in the North East Atlantic or Mediterranean. however, there is a proposal to introduce mandatory logbooks that would require fishing vessel operators to provide data on various of shark and skates (Raja spp.), but not G. galeus (Fleming and Papageorgiou 1996).
10. COST RECOVERY
In the shark fishery of southern Australia, historically the costs of managing the fishery were met by the Australian Commonwealth and State Governments. Following the establishment of Australian Fisheries Management Authority in 1992 with its assumption of day-to-day management of the fishery, most of the costs of management are now met the industry. The Commonwealth Government continues to contribute to the management costs, but most of the costs are now paid by industry. Each holder of a Commonwealth Shark Gill-net Permit or Commonwealth Shark Hook Permit pays an industry levy based on the number of gill-net and/or hook units held. During 1997/98, for example, the budget for the southern Australian shark fishery was A$971,171 of which 72% was contributed by industry and 28% was contributed by Government. This budget covered the costs of management and administration, logbooks, and surveillance and compliance. The costs of research, and assessment were met from Government fisheries research funds (Walker in press).
In New Zealand the Fisheries Act 1996 allows Government to recover from the commercial fishing industry a substantial part of the Government's costs of managing fisheries. At present the costs for managing G. galeus have not been reported by the New Zealand Ministry of Fisheries (Francis and Shallard 1999). No mechanisms for cost recovery have been established for recovering the costs of management in the other fisheries for G. galeus.
11. ACKNOWLEDGEMENTS
I am grateful to John Stevens of CSIRO Marine Research, Hobart, Australia, for permitting me to use material he prepared on the biology of G. galeus; much of this material has been reproduced in Sections 1 and 2 of this report. I also wish to acknowledge the valuable conversations, material and data several people provided in various parts of the world to help me gain insights into the biology and fisheries for G. galeus. I am particularly grateful to Gustavo Chiaramonte of the Museo Argentina de Ciencias Naturales “Bernardino Rivadvia”, Buenos Aires, Argentina, who I travelled with through the shark fishing ports of Argentina and Uruguay. As an able translator Gustavo assisted my understanding of the fishery of the region by introducing me to fishers, fish processors, scientists and fishery managers. In southern Brazil, I wish to acknowledge the valuable discussions and material provided by Carolus Vooren, Nayra Fischer and Monica Peres of the Fundação Universidad de Rio Grande in Rio Grande; Marco Bailon of the Instituto Brasiliero do Meio Ambiente e dos Resursos Naturais Renováveis (IBAMA) in Itajaí; and Jorge Kotas of the Instituto de Pesca in Ubatuba. In South Africa, I was assisted by Marcel Kroese of the Sea Fisheries Research Institute, who accompanied me to several fishing ports and introduced me to people associated with the shark fishing industry. In California, I wish to acknowledge discussions, material and data provided by Mary Larson, Marilyn Beeson, Doyle Hanan and Kristine Barsky of the California Department of Fish and Game, and David Holts of the US National Marine Fisheries Service. Finally, in Australia, I wish to acknowledge my colleagues on the Southern Shark Fishery Assessment Group and professional shark fishers who willingly information, ideas and share data.
12. LITERATURE CITED
Amorim, A.F., C.A. Arfelli and L. Fagundes 1998. Pelagic elasmobranchs caught by longliners off southern Brazil during 1974–97: an overview. Marine and Freshwater Res. 49, 621–632.
Annala, J.H. and K.J. Sullivan 1997. Report from the Fishery Assessment Plenary, May 1997: stock assessment and yield estimates. 381 pp. (Ministry of Fisheries: Wellington)
Annala, J.H., K.J. Sullivan, C.J. O'Brien and S.D. Iball 1998. Report from the Fishery Assessment Plenary, May 1998: stock assessment and yield estimates. 409 pp. (Ministry of Fisheries: Wellington)
Anon 1989. Report of the Study Group on Elasmobranch Fisheries. Report C.M. 1989 G:54, 37 pp. 26–28 April 1989. (International Council for the Exploration of the Sea: Dublin)
Anon 1997. Shark fisher returns first archival tag. 1(2), 15. December 1997. (Australian Fisheries Management Authority: Canberra)
Anon 1998a. Fisheries statistics capture production 1996. FAO Yearbook, Vol. 82, No 140, 678 pp. (Food and Agriculture Organization of the United Nations: Rome)
Anon 1998b. New tags provide exciting insight into school sharks. AFMA News 2(1), 14. May 1998. (Australian Fisheries Management Authority: Canberra)
Archer, J.A.M. 1948. Notes on the vitamin A content of the liver oil of the vaalhaai or soupfin shark (Galeorhinus zyopterus). Commerce and Industries Fisheries and Marine Biological Survey Division Investigational Report No. 10, 7–12.
Barsky, K.C. 1993. History of the commercial California halibut fishery. Department of Fish and Game Fish Bulletin 174, 217–227.
Bass, A. J., J.D. D'Aubrey and N. Kistnasamy 1975. Sharks of the east coast of southern Africa. III. The families Carcharhindae (excluding Mustelus and Carcharhinus) and Sphyrnidae. Oceanographic Research Institute Investigational Report No 38, 1–100.
Bonfil, R. 1994. Overview of world elasmobranch fisheries. FAO Fish. Technical Paper 341, 1–119.
Butterworth, D.S. and A.E. Punt 1992. The Scientific Committee '…Agreed that the MSY Rate Would Most Likely Lie Between 1 and 4%' But Which MSY Rate? Report of the International Whaling Comm. 42:583–591.
Byers, R.D. 1940. The California shark fishery. California Division of Fish and Game Fish Bulletin 26, 23–38.
Cailliet, G.M., D.B. Holts and D. Bedford 1993. A review of the commercial fisheries for sharks on the west coast of the United States. In ‘Shark Conservation’. Taronga Zoo, Sydney. (Eds Pepperell, J.G., West, J. and P.M.N. Woon) pp 13–29. (Taronga Zoo: Sydney)
Capapé, C. and J. Mellinger 1988. Nouvelles données sur la biologie de la reproduction du milandre, Galeorhinus galeus (Linné, 1778), (Pisces, Triakidae) des cotes tunisiennes. Cahiers Biologie Marine 29, 135–146.
Chiaramonte, G.E. 1998. Shark fisheries in Argentina. Marine and Freshwater Res. 49, 601–610.
Chiaramonte, G.E. and J. Corcuera 1995. Explotación comercial y biología de Galeorhinus galeus Linn. 1758 en la Republica Argentina. In 'Informe Nacional 12a reunion del Comité de Animals de CITES. Tiburones Parte 1. 11–14 de setiembre de 1995. Antigua, Guatemala. pp 16.
Coleman, N. and M. Mobley 1984. Diets of commercially exploited fish from Bass Strait and adjacent Victorian waters, south-eastern Australia. Australian Journal of Marine and Freshwater Research 35, 549–560.
Compagno, L.J.V. 1984. FAO species catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 2. Carcharhiniformes. FAO Fisheries Synopsis 125, 251–655.
Compagno, L.J.V., D.A. Ebert and P.D. Cowley 1991. Distribution of offshore demersal cartilaginous fish (class chondrichthyes) off the west coast of southern Africa, with notes on their systematics. South African Journal of Marine Science 11, 43–139.
Corcuera, J., F. Monzon, E.A. Crespo, A. Aguilar and J.A. Raga 1994. Interactions between marine mammals and the coastal fisheries of Necochea and Claromecó (Buenos Aires Province, Argentina). Report of the International Whaling Commission, Special Issue 15, 283–290.
Cousseau, M.B. 1986. Estudios biologicos sobre peces costeros con datos de dos compañas de investigacion realizadas en 1981. VI. el gatuzo (Mustelus schmitti). Publicación de la Comisión Técnica Mixta del Frente Marítimo Argentino-Uruguayo 1, 60–65.
Coutin, P., B. Bruce and L. Paul 1992. New Zealand school sharks cross the Tasman Sea. Australian Fisheries 51,24–25.
de Buen, F. 1952. El tiburón vitamínico. In ‘Apartado del No 7 de la Revista de la Facultad de Humanidades y Ciencias’. pp 87–116. (Universidad de la Republica: Montevideo)
Deriso, R.B. 1980. Harvesting strategies and parameter estimation for an age-structured model. Canadian Journal of Fisheries and Aquatic Sciences 37, 268–282.
Diamond, S. L. and M. Vojkovich 1993. Estimating total effort in the gill and entangling net fishery for California halibut, 1980–1986. Depart. of Fish and Game Fish Bulletin 174, 265–279.
Dow, N.G. 1986. Application of two tag-recapture models to gummy shark, Mustelus antarcticus Günther, and school shark, Galeorhinus galeus (Linnaeus), from the southern Australian shark fishery during 1971–83. Third Southern Shark Assessment Workshop Background Paper. 9 pp. Queenscliff. 28 April-1 May 1986. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Ehrhardt, N.M., G.J. Arena, Z.M. Varela, AJ. Abella, E.M. Sanchez, C.A. Rios and N. de Moratorio 1977a. Evaluacion preliminar de los recursos demersales en el area comun de pesca Argentino-Uruguaya 1975–1976. Informe Técnico No 11, 1–177. (Instituto Nacional de Pesca: Montevideo, Uruguay)
Ehrhardt, N. M., H.C. Nion, H.A. Castaldo and L.C. Barea 1977b. Evaluacion preliminar de los recursos pelagicos del area comun de pesca Argentino-Uruguaya 1975–1976. Informe Técnico No 12, 1–85. (Instituto Nacional Pesca: Montevideo, Uruguay)
Ellis, J.R., M.G. Pawson and S.E. Shackley 1996. The comparative feeding ecology of six species of shark and four species or ray (elasmobrachii) in the north-east Atlantic. Journal of the Marine Biological Association of the United Kingdom 76, 80–106.
Eschmeyer, W.N., E.S. Herald and H. Hammann 1983. Pacific coast fishes of North America. (Houghton Mifflin Company: Boston, Massechusetts)
Fabens, A.J. 1965. Properties and fitting of the von Bertalanffy growth curve. Growth 29, 265–289.
Ferreira, B. P. and C.M. Vooren 1991. Age, growth, and structure of vertebrae in school shark Galeorhinus galeus (Linnaeus, 1758) from southern Brazil. Fishery Bulletin 89, 19–31.
Fitzmaurice, P. 1979. Tope, Galeorhinus galeus (L), migrations from Irish coastal waters and notes on Irish specimens. 26–33. (UK)
Fleming, E.H. and P.A. Papageorgiou 1996. Shark fisheries and trade in Europe. In ‘The World Trade in Sharks a Compodium of TRAFFIC's Regional Studies’. pp 457–604. (TRAFFIC International: Cambridge)
Francis, M.P. 1998. New Zealand shark fisheries: development, size and management. Marine and Freshwater Research 49, 579–591.
Francis, M.P. and K.P. Mulligan 1998. Age and growth of New Zealand school shark, Galeorhinus galeus. New Zealand Journal of Marine and Freshwater Research 32, 427–440.
Francis, M.P. and Shallard, B. 1999. New Zealand shark fishery management. xx - xx. In R. Shotton (Ed) Case Studies on the Management of Elasmobranch Fisheries. FAO. Tech. Pap. No. xxx.
Freer, D.W.L. 1992. The commercial fishery for sharks in the South-western Cape, with an analysis of the biology of the two principal target species, Callorhynchus capensis Dumeril and Galeorhinus galeus Linn. MSc Thesis, University of Cape Town, Cape Town. 103 pp.
Giulietti, N. and R. de Assumpcao 1995. Industria pesqueira no Brasil. Agricultura em São Paula, SP, 42, 95–127.
Grant, C. J., R.L. Sandland and A.M. Olsen 1979. Estimation of growth, mortality and yield per recruit of the Australian school sharks, Galeorhinus australis (Macleay), from tag recoveries. Australian Journal of Marine and Freshwater Research 30, 625–637.
Gulland, J.A. 1955. On the estimation of population parameters from marked members. Biometrika 42, 269–270.
Gulland, J.A. 1969. Manual of methods for fish stock assessment. FAO Manual in Fish. Sci., No 4.
Hanan, D.A., D.B. Holts and L.C. Atilo 1993. The California drift net fishery for sharks and swordfish, 1981–82 through 1990–91. Depart. of Fish and Game Fish Bulletin 175, 1–95.
Harrison, AJ. 1970. Stock assessment of school shark, Galeorhinus australis. Second Meeting, South Eastern Fisheries Committee Shark Research Group. 5 November 1970. In ‘Proceedings of the Shark Assessment Workshop, South East Fisheries Committee Shark Research Group. Melbourne. 7–10 March 1983’. 20 pp. (Department of Primary Industry: Canberra)
Hart, J.L. 1973. Pacific fishes of Canada. Bull. Fish. Res. Board Canada, 740 pp.
Hayes, E. 1996. New Zealand overview. In ‘The world trade in sharks: a compendium of TRAFFIC'S regional studies’. (Eds pp 751–790. (TRAFFIC International: Cambridge)
Herald, E.S. and W.E. Ripley 1951. The relative abundance of sharps and bat stingrays in San Francisco Bay. California Fish and Game 37, 315–329.
Holden, M.J. 1974. Problems in the rational exploitation of elasmobranch populations and some suggested solutions. In ‘Sea Fisheries Research’. (Eds Harden-Jones, F. R) pp 117–137. (Halsted Press: New York)
Holden, M.J. and R.G. Harrod 1979. The migrations of tope, Galeorhinus galeus (L), in the eastern North Atlantic as determined by tagging. Journal du Conseil International pour l' Exploration de la Mer 38, 314–317.
Holts, D.B. 1988. Review of US west coast commercial fisheries. Marine Fisheries Review 50, 1–16.
Jones, R. 1966. Manual of methods for fish stock assessment. Part IV. Marking. FAO Fisheries Technical Paper, Supplement 1.
Jow, T. 1993. The California halibut trawl fishery. Dept. of Fish and Game Fish Bull. 174, 229–241.
Kesteven, G.L. 1966. Stock assessment for school shark, Galeorhinus australis. Technical Session. Southern Pelagic Project committee. 24–29 Aagust 1966. In ‘Proceedmgs pf flie Shark Assessment Workshop, South East Fisheries Committee Shark Research Group, 7–16 March 1983’. 20pp. (Department of Primary Industry: Canberra: Melbourne)
Kirkwood, G.P. 1984. Etsimation of shark mortality rates from tag-recapture data, talking account of gillnet selectivity. Second Southern Shark Assessment Workshop Background Paper. 11 pp. Melbourne, 21–23 August 1984. (CSIR.O Marine Laboratories: Sydney)
Kirkwood, G.P. and T.I. Walker 1986. Gill net mesh selectivities for gummy shark, Mustelus Antarcticus Günther, taken in south-eastern Australian waters. Australian Journal of Marine and Freshwater Research 37, 689–697.
Kotas, J. E., M. da Rocha Gamba P.C. Conolly, M. Hostim-Silva, R.C. Mazzoleni and J. Pereira 1995. Gillnet activities in southern Brazil. 48 pp. (Centro de Pesquisa e Extensão Pesqueira do Sudeste, Instituto Brasileiro do Meio Ambiente e dos Resursos Naturais Renováveis: Itajaíi, Santa Catarina, Brazil
Kroese, M., W.H. Sauer and A.J. Penney 1995. An overview ofshark catches and bycatches in South African fisheries. SCRS/95/112, 1–23. (Sea Fisheries Research Institute: Rogge Bay, Cape Town)
Kroese, M. and W.H.H. Sauer 1998. Elasmobrnnch exploitation in Africa. Marine and Freshwater Research 49, 573–577.
Marín, Y., F. Brum, L.C. Barea and J.F. Chocca 1998. Incidental catch associated with swordfish longline fisheries in the south-west Atlantic Ocean. Mar. and Freshwater Res. 49, 633–639.
Maurin, C. and M. Bonnet 1970. Poissons des cotes nord-ouest africaines (Compagnes de la ‘Thalassia’, 1962 et 1968). Revue des Travaux Instituí de Pêches MaritÍmes NanÍes 34, 125– 170.
McGregor, G. 1994. Tasman Sea no barrier to tagged school shark. Seafood N. Z.. April 1994, 19–20.
McLoughlin, K.L. and J.D. Stevens 1994. Gill-net mesh selectivities for two species of commercial carcharhinid shark taken in northern Australia. Australian Journal of Marine and Freshwater Research 45, 521–534.
Menni, R.C. and A.E. Gozstonyi 1982. Benthic and semidemersal fish association in the Argentine Sea. Studies on Neotropical Fauna and Environment 17, 1–29.
Miller, K.E. 1993. A comparison of California halibut catches by 8- and 8.5-inch mesh gill and trammel nets of southern California. 174, 281–301.
Moulton, P.M., T.I. Walker and S.R. Saddlier 1992. Age and growth studies of gummy shark, Mustelus antarcticus Günther and school shark, Galeorhinus galeus (Linnaeus), from southern-Australian waters. Australian Journal of Mar. Freshwater Res. 43, 1241–1267.
Muñoz-Chápuli, R. 1984. Ethologie de la reproduction chez oueloues requins de 1'Atlantique nord-est. Cybium 8, 1–14.
Muñoz-Chápuli, R., G. Notarbartolo di Sciara, B. Seret and M. Stehmann 1993. The status of the elasmobranch fisheries in Europe. Report of the Northeast Atlantic Subgroup of the IUCN Shark Specialist Group.
O'Brien, J.W. and J.S. Sunada 1994. A review of the southern California experimental drift longline fishery for sharks. CalCOFI Report 34, 222–229.
Olsen, A.M. 1953. Tagging of school shark, Galeorhinus australis (Macleay) (Carcharhinidae), in south-eastern Australian waters. Australian Journal of Mar. and Freshwater Res. 4, 95–104.
Olsen, A.M. 1954. The biology, migration and growth rate of the school shark, Galeorhinus australis (Macleay) (Carcharianidae) in south-eastern Australian waters. Australian Journal of Marine and Freshwater Research 5, 353–410.
Olsen, A.M. 1959. The status of the school shark fishery in south-eastern Australian waters. Australian Journal of Marine and Freshwater Research 10, 150–176.
Olsen, A.M. 1962. Growth and migration of sharks through tagging experiments. In ‘Eleventh Pacific Science Congress’. 1962. Honolulu, Hawaii, USA.
Olsen, A.M. 1984. Species synopsis of school shark, Galeorhinus australis (Macleay, 1881). 42 pp. (Food and Agriculture Organisation of the United Nations: Rome)
Paul, L.P. 1988. School shark. New Zealand Fisheries Assessment Research Document 88/27, 32 pp. (New Zealand Ministry of Agriculture and Fisheries: Wellington)
Paulik, G.J. 1963. Estimates of mortality rates from tag recoveries. Biometrics 19, 28–57.
Peres, M.B. and C.M. Vooren 1991. Sexual development, reproductive cycle and fecundity of the school shark Galeorhinus galeus off southern Brazil. Fishery Bulletin 89, 655–667.
Praderi, R. 1990. Mortality of dolphins in shark gillnets fisheries off Uruguay. In ‘International Whaling Commission Symposium on mortality of cetaceans in passive nets and traps’. 20–21 October 1990. La Jolla. pp 1–14)
Prince, J.D. 1991. An assessment of the south-eastern Australian shark fishery. (Consultant Report to Bureau of Rural Resources: Perth)
Punt, A.E. and T.I. Walker 1998. Stock assessment and risk analysis for the school shark (Galeorhinus galeus) off southern Australia. Marine and Freshwater Res. 49, 719–731.
Punt, A.E., Xiao, Y. and B.L. Taylor 1996. Standardisation of commercial catch and effort data for school shark Galeorhinus galeus (1927–94). Southern Shark Fishery Assessment Group. Report No. SS/96/D7. (CSIRO Marine Research: Hobart, Tasmania, Australia)
Ripley, W.E. 1946. The soupfin shark and the fishery. California Division of Fish and Game Fish Bulletin 64, No. 64, 7–37.
Ripley, W.E. and R.A. Bolomey 1946. The relation between the biology of the soupfin shark to the liver yield of vitamin A. California Depart. Fish and Game Fish Bulletin, No. 64, 39–72.
Rose, D.A. 1998. Shark fisheries and trade in the Americas Volume 1: North America. 201 pp. (TRAFFIC North America: Washington D.C)
Schnute, J. 1985. A general theory for analysis of catch and effort data. Canadian Journal of Fisheries and Aquatic Sciences 42, 414–429.
Schnute, J. 1987. A general fishery model for a size-structured fish population. Canadian Journal of Fisheries and Aquatic Sciences 44, 924–940.
Siccardi, E. 1950. El problema del tiburón en la economía e industrial. In ‘Primer Congreso Nacional de Pesquerías Marítimas e Industrias Derivadas’. 24–29 de octubre 1949. Actas. Mar del Plata. 2, 121–146.
Simpfendorfer, C.A. and P. Unsworth 1998. Gill-net mesh selectivity of dusky sharks (Curcharhinus obscurus) and whiskery sharks (Furgaleus macki) from south-western Australia. Marine and Freshwater Research 49, 713–718.
Sluczanowski, P.R.W., T.I. Walker, H. Stankovic, S.Forbes, J. Tonkin, N.H. Schenk, J.D. Prince and R. Pickering 1993. Sharksim: a computer graphics model of a shark fishery. In ‘Shark Conservation’. 24 February 1991. Taronga Zoo, Sydney. (Eds Pepperell, J., West, J. and Woon, P) pp 45–47. (Zoological Parks Board of NSW: Sydney)
Stevens, J.D. 1990. Further results from a tagging study of pelagic sharks in the north-east Atlantic. Journal of the Marine Biological Association of the United Kingdom 70, 707–720.
Stevens, J.D. and G.J. West 1997. Investigation of school and gummy shark nursery areas in south eastern Australia. FRDC Project 93/061. 76 pp. July 1997. (CSIRO Marine Research: Hobart)
Taylor, B.L. 1997. Movement modelling shell for school shark (Galeorhinus galeus) in the Australian Southern Shark Fishery: A user's guide to SSMOVE (Version 1). In ‘Southern Shark Tagging Project. Final report to Fisheries Research and Development Corporation’. (Eds Walker, T. I., L.P. Brown and N.F. Bridge) pp 57–61. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Teirney, L.D., A.R. Kilner, R.B. Millar, E. Bradford and J.D.Bell 1997. Estimation of recreational harvests from 1991–92 to 1993–94. New Zealand Fisheries Assessment Research Document 97/15, 43 pp. (Ministry of Fisheries: Wellington)
Tenison-Woods, J.E. 1882. Sharks. In ‘Fish and Fisheries of New South Wales’. (Goverment Printer: Sydney)
Van der Elst, R. and R.Vermeulen 1986. Sharks and stingrays. 398 pp. (Struik: Cape Town)
Van Der Molen, S., G. Caille and R. Gonzalez 1998. Bycatch of sharks in Patagonian coastal trawl fisherics. Marine and Freshwater Research 49, 641–644.
Vooren, C.M. 1990. Análise da estatÍstica da pesca de elasmobrânquios demersais no porto de Rio Grande, de 1973 a 1986. Ciência e Cultura 42, 1106–1114.
Walker, T.I. 1970. Stock assessment of school shark, Galeorhinus australis. First Meeting, South Eastern Fisheries Committee Shark Research Group. 8 June 1970. In ‘proceedings of the Shark Assessment Workshop, South Eastern Fisheries Committee Shark Research Group, Melbourne. 7–10 March 1983’. 4 pp. (Department of Primary Industry: Canberra)
Walker, T.I. 1976. Effects of species, sex, length and locality on the mercury content of school shark Galeorhinus australis (Macleay) and gummy shark Mustelus antarcticus Guenther from south-eastern Australian waters. Aust. J. Marine and Freshwater Research 27, 603–616.
Walker, T.I. 1986. Southern Shark Assessment Project. Second Review. October 1986. Marine Science Laboratories Progress Review 66,48 pp. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Walker, T.I. 1988. Mercury concentrations in edible tissues of elasmobranchs, teleosts, crustaceans and molluscs from south-eastern Australian waters. Australian Journal of Marine and Freshwater Research 39, 39–49.
Walker, T.I. 1989a. Methods of tagging adopted in the southern shark fishery. In Tagging - Solution or Problem? Australian Society for Fish Biology Workshop'. 21–22 July 1988. Sydney. (Eds Hancock, D. A.) pp 105–108. (Australian Government Publishing Service: Canberra)
Walker, T.I. 1989b. Stomach contents of gummy shark, Mustelus antarcticus Gunther and school shark, Galeorhinus galeus (Linnaeus) from south-eastern Australia. In' Southern Shark Assessment Project- Final FIRTA Report: March 1989'. pp 24. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Walker, T.I. 1991. Fishery simulation model for sharks applied to the gummy shark, Mustelus antarcticus Günther, from southern Australian waters. In 'Southern Shark Database Project-Final FIRDTA Report: April 1991 Marine Science Laboratories Internal Report No. 189'. (Eds Walker. T. I., Gason, A. S., Coutin, P. C., Woolcock, J. L. and Brown, L. P.) pp 21. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Walker. T.I. 1992. A fishery simulation model for sharks applied to the gummy shark, Mustelus untarcticus Gunther, from southern Adstralian waters. Australian Journal of Marine and Freshwater Research 43, 195–212.
Walker, T.I. 1994a. Fishery model of gummy shark, Mustelus antarcticus, for Bass Strait. In ‘Resource Technology '94 New Opportunities Best Practice’. 26–30 September 1994. University of Melbourne, Melbourne. (Eds Bishop, 1.) pp 422–438. (The Centre for Geographic Information Systems & Modelling. The University of Melbourne: Melbourne)
Walker, T.I. 1994b. Stock assessments of the gummy shark, Mustelus antarcticus Glinther, in Bass Strait and off South Australia. In ‘Population Dynamics for Fisheries Management’. 24–25 August 1993. Perth. (Eds Hancock, D. A.) pp 173–187. (Australian Government Printing Service: Canberra)
Walker, T.I. 1995a. Evaluation of recent seasonal closures in the Southern Shark Fishery. Report to Australian Fisheries Management Authority II pp. 5 May 1995. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Walker, T.I. 1995b. Stock assessment of the school shark, Galeorhinus galeus (Linnaeus), off southern Australia by applying a delay-difference model. Report to Southern Shark Fishery Assessment Group. 28 pp 27 Feb-3 Mar 1995. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Walker.T. 1. (in press). Southern Australian Shark Fishery Management. 37 pp. (Food and Agriculture Organization of the United Nations: Rome)
Walker, T. 1., L.P. Brown and N.F. Bridge 1997a. Southern Shark Tagging Project. Final report to Fisheries Research and Development Corporation. November 1997. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Walker, T.I. and R..J. Hudson 1995. Coinparison of shark catches firm gill-nets of various mesh-sizes on FV Lincoln in the Great Australia Bight. Report to Southern Shark Fishery Assessment Group Workshop. 6pp. Canberra, 13–15 December 1995. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Walker, T.I., D. Johnson, D. Brown and K. MoLoughlin 1997b. Fisheries assessment report , the southern shark fishery 1996. 56 pp (Australian Fisheries Management Authority: Canberra)
Walker, T.I., P.L.Moulton, N.G.Dew and R.S.Saddlier 1989a. Southern Shark Assessment Project -Final FIRTA Report: March 1989. 43 pp. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Walker, T.I., P.L. Moulton and R.S. Saddlier 1989b. Reproduction studies of four species of shark and one species of elephant fish commercially fished in southern Australia. In ‘Southern Shark Assessment Project - Final FIRTA Report: March 1989’. 43 pp. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Walker, T.I., B.L. Taylor, R.J. Hudson and N.F. Bridge 1998b. Southern shark catch and effort 1970– 97 report to Australian Fisheries Management Authority. 32 pp. July 1998. (Marine and Freshwater Resources Institute: Queenscliff, Victoria, Australia)
Walker, T.I. 1999. Southern Austrlian Shark Fisheries Management. In R. Shotton (Ed). Case Studies on the Management of Elasmobranch Fisheries, xx - xx. FAO. Tech. Pap. No. xxx.
Ward, R.D. and M.G. Gardner 1997. Stock structure and species identification of school and gummy sharks in Australian waters. Project FRRF 93/11 and FRDC 93/64 92 pp. February 1997. (CSIRO Marine Research: Hobart, Tasmania, Australia)
Wheeler, A. 1969. The fishes of the British Isles and north-west Europe. 613 pp. (MacMillan: London)
Whitley, G.P. 1940. The fishes of Australia. Part I. The sharks, rays, devilfish, and other primitive fishes of Australia and New Zealand. Australian Zoological Handbook. 280 pp. (Royal Society of New South Wales: Sydney)
Xiao, Y. 1995a. Integration of standardization of catch and effort with production models for stock assessment. Prepared for Southern Shark Fishery Assessment Group Workshop. 29 pp. 27 Feb-3 Mar 1995. (CSIRO Marine Research: Hobart, Tasmania, Australia)
Xiao, Y. 1995b. Stock Assessment of the School Shark Galeorhinus galeus (Linnaeus) off Southern Australia by Schaefer production model. Report to Southern Shark Fishery Assessment Group Workshop. 55pp. 27 February-3 March 1995. (CSIRO Marine Research: Hobart, Tasmania, Australia)
Xiao. Y. 1996. A framework for evaluating experimental designs for estimating rates of fish movement from tag recoveries. Can. J. of Fisheries and Aquatic Science 53, 1272–1280.
