University of British Columbia, Vancouver, Canada
1.1 The resource
Throughout Canadian fishing history, harvesting of shark has been of minor importance with one exception: the British Columbia (BC) vitamin A shark-liver fishery of the 1940s. This fishery was based almost exclusively on picked dogfish (Squalus acanthias), known locally as dogfish. On the west coast of North America, the tope shark (Galeorhinus galeus) (locally known as soupfin shark) is the best species for vitamin A production. However, its distribution is more southerly along the coast of California (Roedel and Ripley 1950).
In addition to the different fisheries for dogfish, attempts have been made to commence a fishery for sixgill shark (Hexanchus griseus) in BC. However, these efforts were unsuccessful because of concerns over the sustainability of such a fishery given the insufficient knowledge about the resource (M. Saunders, Department of Fisheries and Oceans (DFO) Pacific Biological Station, per. comm. Oct. 1997). Apart from the small directed fishery for picked dogfish, only minor incidental catches of other sharks have been landed by BC fisheries (e.g. tope shark, sixgill sharks, salmon sharks, Lamna ditropis, and blue sharks, Prionace glauca). At least three species of skates (Raja spp.) have been landed at least since 1986, but there is little information on, and no management of, this fishery. This study focuses on the dogfish which is the only shark with a history of commercial exploitation in BC and also the only elasmobranch for which some degree of fishery management exists on the west coast of Canada.
The commercial exploitation of dogfish in BC has been recorded for at least 126 years and prehistoric records confirm the common use of the dogfish by North American natives in the region since about 4000–4600 b.p. (Ketchen 1986). At present, the fishery is a minor activity based mostly on incidental catches of the trawl and hook and line demersal fisheries; only a few vessels fish directly for dogfish. At present, about 60% of the landings come from the longline fleet while most of the remaining catch is landed by trawlers which also discard large quantities of dogfish at sea.
1 The British Columbia dogfish fishery has a long history well rooted in the 19th century, and was once the most
valuable fishery in the west coast of Canada. Yet, there are still important gaps in information regarding the
present and historical status and management of this fishery. Another salient aspect of this fishery is that its
management has always been limited. The gaps in information and the limited management of the fishery are
both reflected in the quantity and the quality of information presented in various sections throughout this report,
especially those regarding management. Despite this, and considering the limited occurrence of shark fisheries
management systems worldwide (Bonfil 1994), a study on the dogfish fishery of British Columbia is still
relevant in the global context of shark fisheries management. First, because this case represents a rare instance
of an under-developed fishery for sharks within a relatively advanced management system, and second, because
of the historical importance of the different phases the fishery has gone through.
In the last 100 years, the BC dogfish has varied in its prominence in the local fisheries. At one time it was the prime source of wealth for local fishermen, but later became a heavily subsidised activity which was naively proposed as a solution to a perceived “marine plague” problem.
Earlier, the fishery was specifically directed towards dogfish but later it became a market-constrained secondary fishery supplied mainly from bycatches. The earlier directed fishery relied on demand for liver oil and to a lesser extent for human consumption of its meat. The best years for the dogfish fishery were the late 1930s and the 1940s when demand for shark livers to produce vitamin A made dogfish a species highly sought-after worldwide. During 1944 dogfish was the most valuable fishery on the west coast of Canada (Ketchen 1986), but by 1950 the commercial production of synthetic vitamin A market caused its collapse though already the fishery was showing signs of overfishing. Since then, dogfish landings have been constrained by low market demand. Despite efforts to revive the fishery, supplies mainly come from incidental catches from fisheries directed at other species.
Because the current dogfish fishery is a marginal activity in Western Canada, it is carried out and managed under the broader scope of the demersal fisheries of BC. Thus, most of the recent management and exploitation of dogfish depends on issues related to the more valuable species in the BC groundfish fishery such as rockfish (Sebastes spp.), Pacific hake (Merluccius productus) and Pacific halibut (Hippoglossus stenolepis).
Little is known about the stock structure of dogfish in the NE Pacific. It is believed that there is a “coastal stock” residing in waters of the Strait of Georgia-Puget Sound area and an “offshore stock” that extends from Alaska to Baja California (Saunders et al. 1985, Ketchen 1986). There are no population genetic studies to test this hypothesis which is based mostly on tag-return data, differential concentration of mercury in the flesh depending on the geographic area, and anecdotal observations from fishermen about dogfish movements. Ketchen (1986) points out that although most short-term tag returns support this scenario, there are longer-term recaptures that demonstrate movement of dogfish from BC as far south as central Baja California, Mexico, and trans-Pacific movements to waters off Japan. Ketchen notes though that data from driftnet operations throughout the North Pacific suggest an insignificant east-west interchange of dogfish.
The pattern of dogfish availability during the boom of the liver fishery and the tag return data suggest seasonal migrations of the offshore dogfish stock to the south in autumn and winter and back to BC-Washington during spring and summer (Holland 1957, Ketchen 1986). Nevertheless, knowledge about the movements of the different stocks of dogfish in the region and the interrelationships between such stocks is still incomplete (Ketchen 1986). The dogfish fishery is managed consistenly with this stock structure scenario. Thus, stock assessment and management regulations (TAC's and IVQ's) are provided for the coastal and offshore stocks separately.
1.2 Species composition of fishery
Picked dogfish is the only shark species regularly landed in the fisheries of BC. Some tope shark might be landed occasionally but separate statistics did not exist for this species until 1997. As mentioned, an experimental fishery for sixgill sharks took place in the early 1990s but was not allowed to develop. The landings of skates are composed mainly of big skate (Raja binoculat), longnose skate (R. rhina) and deep-sea skate (R. abyssicola), although a few black skates (R. kincaidi) are also caught.
1.3 Distribution of fishery
The picked dogfish is an abundant cosmopolitan species inhabiting temperate and cold waters (Compagno 1984). In the NE Pacific Ocean it is found from the Bering Sea (no farther north or west than 68° 35' N, 176°25' W) to southern Baja California, Mexico (San Martin Island; 30°31' N, 116° 10' W) (Ketchen 1986). Within this region the centre of abundance seems to be located between northern BC and southern Washington, declining in abundance southward through Oregon and California.
Picked dogfish is exploited throughout its geographic range and is the most important single species of shark exploited commercially in the world (Compagno 1990). According to FAO statistics, the largest catches of picked dogfish in the period 1990–94 were taken off the NE coast of USA and Eastern Canada and in the NE Atlantic Ocean (Figure 1). Other important catches were taken off the NW coast of USA and Western Canada and around New Zealand. However, these figures are not totally accurate as landings of picked dogfish in some countries are reported only as “dogfish” or “sharks”. As it is impossible to separate those statistics by species, they could not be shown in Figure 1.
Share of world catches of dogfish by FAO statistical areas 1990–94 Dogfish catches not reported to FAO as picked dogfish are not included.
Most of the catches of the NE Pacific dogfish fishery are taken between Oregon and Northern BC. Although there is relatively high variability in the year-to-year proportion of the total catches of dogfish taken by the USA and Canada in this region, the two countries have maintained approximately similar proportions of the landings over the last decade. Some foreign nations. e.g. Poland, have fished sporadically for dogfish in BC waters.
Dogfish are very common in BC where they are widely distributed along the continental shelf and slope and this shark is likely to occur almost every place trawls are used (Figure 2). Ketchen (1986), based on historical records dating from the peak of the fishery (1941–1949) identified the most important commercial fishing grounds for dogfish in BC as: (1) Hecate Strait and in particular the flats extending east of the Queen Charlotte Islands (Statistical Areas 5C and 5D; Figure 3), (2) the Strait of Georgia - located between southern Vancouver Island and the BC mainland - and its convergence with Puget Sound (Area 4B), and (3) the south west coast of Vancouver Island around La Pérouse and Swiftsure Banks (Area 3C). More recent analyses based on at-sea observer data for the 1996 groundfish trawl fishery (excluding data for the Strait of Georgia) confirm wide occurrence of dogfish along the BC coast. These data also indicate that dogfish CPUE is higher around the eastern portion of Dixon Entrance off the NE Queen Charlotte Islands, in the central-southern part of the Hecate Strait, around Mitchell's Gully in Queen Charlotte Sound, and off the southwest coast of Vancouver Island (Figure 4). Note that these observations pertain to catches of dogfish, not necessarily to landings.
1.4 Associated species either as bycatch or discards
The landings of dogfish in BC are mostly bycatch from the hook and line and trawl fisheries. although a few of the hook and line vessels target dogfish specifically. Thus it is inappropriate to consider other species caught with dogfish as bycatches of the dogfish fishery. In fact, usually dogfish is the bycatch from fisheries targeting other species, e.g. rockfish, hake and flatfishes. An exception to this pattern are the 10–15 longline boats that target dogfish mainly in the Strait of Georgia (D. Trager DFO, per. comm., Feb. 1998). Because of the lack of an at-sea observers programme or data collection programme for the longlining fleet no information exists on the bycatches of other species in this fishery.
Along the west coast of the US, dogfish are generally associated with several groundfish species, probably as an important predator of some of them. Most commonly, dogfish have a strong association with hake, but are also caught with American sanddab (Citharichthys sordidus), English sole (Parophrys vetulus), rex sole (Glyptocephalus zachirus), arrowtooth flounder (Atheresthes stomias), Dover sole (Microstomus pacificus), sablefish (Anoplopoma fimbria), yellowtail rockfish (Sebastes flavidus), walleye pollock (Theragra chalcogramma) and lingcod (Ophiodon elongatus) (Jay 1996).
Estimated spatial abundance (annual average CPUE) of dogfish in BC during 1996 based on observer's data. Black cells show highest average CPUE.
2. DEVELOPMENT AND CURRENT STATUS OF FISHING METHODS
2.1 The harvesting process
The dogfish fishery of BC has traditionally concentrated most of its effort in the Strait of Georgia, and then on fishing grounds around the banks of the south west coast of Vancouver Island and the Hecate Strait. Although the historical record of fishing gears and vessels is limited, during the history of the fishery from about 1940s onwards longlines (known as set-lines) and trawl nets have dominated the fishery. Special permits for sunken gillnets have been granted for short periods in the Strait of Georgia during the last 45 years, but as a rule they have not been permitted in BC for several decades.
Map of the coast of British Columbia showing the major groundfish management areas
The trawl and longlining fleets exploit slightly different portions of the dogfish stocks. Longlines - which are set almost exclusively on the bottom - catch dogfish that tend to be larger due to their higher selectivity and the natural distribution of dogfish in the water column (adult dogfish tend to be more demersal while the juveniles and young adults feed mostly in mid-water). Usually better quality and larger fish are landed by longliners and this is why most landings are by this fleet. Fish quality is better because trips are shorter and thus they deliver fresher product and because fish are not crushed and damaged as happens in trawl cod-ends. In recent times, the longlining fleet that supplies the dogfish export market mainly fishes in the Strait of Georgia and off the west coast of Vancouver Island. The bottom (rockfish and flatfish) and mid-water (hake) trawl fleets operate along the entire coast but land only a small percentage of the dogfish catch. They mostly discard at sea (on average, about 55% of the trawl catch since 1979; see Table 1). Because bottom trawling is restricted in the Strait of Georgia to a few small areas, the trawl fleet tends to exploit a greater mixture of adults and juveniles than from the offshore stock along the coast. The longline fleet catches chiefly large adults of both the offshore (SW coast of Vancouver Island) and coastal stocks (St. of Georgia).
Spatial distribution of fishing effort intensity in the demersal fisheries of BC during 1996
Top panel shows all tows observed, bottom panel is based only on tows where dogfish was caught. Note the virtual perfect match of data, indicating that dogfish is found almost everywhere along the BC coast. Data from the at-sea observer programme for the groundfish trawl fishery, DFO. Black denotes highest effort rate
Data for 1943–1953 from Ketchen (1986), Table 15.
Data for 1953–1959 from Ketchen (1986), Table 17.
Data for 1972–1979 are only for Strait of Georgia from Ketchen (1986), Appendix 10.
Data for 1979–1996 from Thompson (1995) and Saunders (1997); data 1994–96 preliminary.
2.1.2 Historical overview of the fishery
Ketchen (1986) provides a detailed and comprehensive historical account of the BC dogfish fishery which is summarized here. Use of dogfish by the natives of the region has been estimated to go back 4000–4600 years (based on dogfish spines found in a shell-midden at Friendly Cove, Vancouver Island). Historical accounts from the post-contact era indicate that the people of the west coast of Canada had several uses for dogfish; some used the skins for polishing and finishing wood, a few ate the flesh, and most used the liver oil for tanning hides and water proofing and preservation of canoes and other uses. Among the Haida of the Queen Charlotte Islands, dogfish were one of the fishes used as crests in the decoration of totem poles.
Ketchen identifies five phases in the commercial exploitation of dogfish in BC. First, an early period (1870–1916) when dogfish liver and body oils were used as an industrial lubricants and lighting fuel, followed by a two decade period when dogfish oil and fishmeal were used in, or as substitutes for, fertiliser (1917–39). The years 1937 to 1950 marked the golden era of the liver-oil fishery for the production of Vitamin A. This gave way to a period (1951–74) of failed and often subsidised attempts to reinitiate a fishery. The final stage - which started in 1977 - constituted a “revival” of the dogfish fishery for the export of its meat. From 1987 to the present has been a continuation of this last phase outlined by Ketchen. The following paragraphs summarize the main features of each of the five historical phases of the fishery.
The first records of commercial exploitation of dogfish in BC indicate that by 1870 the dogfish fishery had steadily developed - exclusively by native fishermen - and had surpassed in importance the whaling industry with a total production of 50 000 gallons of dogfish oil. A large proportion of the oil was exported to Britain as excessive duties prevented the development of a market in the neighbouring United States. Dogfish were a prime resource in those days: in 1876 dogfish oil exports constituted at least 24% of the total value of fish exports. Dogfish oil had use as a lubricant and lamp fuel: some lighthouses in BC relied exclusively on dogfish oil and the coal mining industry on Vancouver Island relied on its oil for naked-flame lamps. In the opinion of Anderson, then inspector of fisheries for British Columbia, the dogfish resource was a source of employment to a large number of people along the coast of BC and could continue to be so for a long time given the practically inexhaustible supply. He also saw in the dogfish fishery a potential for the creation of a large flow of cash and in 1879 the Skidegate Oil Company was established in the Queen Charlotte Islands to produce dogfish oil, employing 16 native fishermen and five in shore labor. Production of dogfish oil reached a high of 1 300 000t in 1883, equivalent to 9000–14 000t round weight (Figure 5). Despite the detailed historical account by Ketchen, no information is provided about the boats and gear used during the early period of the fishery. Nevertheless, it can be assumed that the fishery used traditional canoes and fishing gear employed for other fisheries by the natives of BC. The fishing technology of the native peoples was diverse and included ingenious and efficient gears and methods. Indians of Western Canada are known to have used wooden hooks with boned barbs and stone sinkers attached to lines made of twisted cedar fibre, animal intestines or giant kelp. Up to 10–15 lines could be deployed from a canoe manned by two natives (Alverson et al. 1964). One method of dogfish fishing used lures made with pieces of salmon tied to a wooden stick. The lure was sunk and slowly raised to the surface with the dogfish in pursuit. Once the dogfish reached the surface and approached the canoe, the fish were grabbed by the tail and tossed into the boat (Stewart 1982). During the early period of the commercial dogfish fishery the main fishing ground was the Strait of Georgia until the Skidegate Oil Co. started exploiting the lucrative grounds on the flats of the western Hecate Strait. Ketchen speculates that a mixture of circumstances leading to sluggish demand (new lubricants derived from petroleum, the advent of new lighting fuels and the electric lamp, etc.) might have initiated the decline of the dogfish fishery from the 1890s until its collapse in the mid 1910s.
Towards the end of the 1920s the dogfish fishery revived as a result of shortages of meat in the US - apparently caused by WWI - and the demand for dogfish for industrial uses. These uses included production of fish meal for animal food, use of liver oil in poultry and medicine preparations, as a base for insecticide sprays, for leather tanning, and use of dogfish body oil and lower-grade liver-oil for tempering steel and manufacture of sheep and cattle dips. During these years, seven plants operated in the Strait of Georgia and a freighter was converted into a floating dogfish reduction plant. As the global markets for fish oil and meal grew, landings of dogfish increased through the 1920s. Baited set-lines (longlines) were the main gear used followed by sunken gillnets (Table 2). A few otter trawlers fished then but it is unlikely that they landed significant amounts of dogfish; trawling did not expand on the NE Pacific until after 1933 (Alverson et al. 1964). The pattern of production in the meal industry usually involved salmon reduction during the summer and dogfish reduction in winter. The depression of 1929 caused the prices for dogfish and consequently the catches, to fall sharply. The fishery picked up again during the 1930s, but not before several processing plants had gone bankrupt.
Proportion of discards of dogfish in the operarations of the groundfish fishery of BC 1979–95 Data from Thompson (1995) and Saunders (1997)
The period 1937–50 was the major period of the dogfish fishery. The discovery around 1927 that dogfish liver oil contained higher concentrations of vitamin A than cod liver oil was mainly responsible for the revival of the fishery. During 1936–37 dogfish liver oil became the preferred ingredient to enrich cattle and poultry feed together with other fish oils that had high concentrations of vitamin D. The northwest US was the main market for this liver oil. WW II and the development of an efficient and economical process for extracting vitamin A from dogfish livers generated the high demand for dogfish that resulted in the boom of the fishery; prices rose in the US and to a lesser extent in Vancouver (see Figure 6). Effort and catch increased, more dogfish were processed at sea, and as the fishery developed less whole dogfish and more livers were landed. British Columbian catches of dogfish peaked in 1944 at 31 000t. In the same year, dogfish was most valuable fish in BC and 4th in Canada. In this period, the fishery expanded beyond the Strait of Georgia and Puget Sound into shallow as well as deep-water grounds in the Hecate Strait. The use of sunken gillnets to catch dogfish in the Strait of Georgia was widespread in 1939, but during 1940–44 increasing pressure from lingcod fishermen caused progressively tougher regulations eventually prohibiting their use by the end of the 1940s. At the same time, the incorporation of the power-driven drums on gillnet vessels and the use of cotton discarded salmon gillnets as sunken gillnets for dogfish became increasingly common in open coastal waters after 1942. Otter trawls also entered the fishery, especially after 1937 when the number of licences for this gear began to increase. However, otter trawls had lower size-selectivity than other gears. The stocks started to show signs of overfishing in 1944 (Holland 1957, cited by Ketchen 1986) with supplies of larger dogfish declining for all types of gears but especially for longlines. After 1944 production fell as signs of overfishing continued (increased difficulty to find larger dogfish, falling catch rates in gillnets, and indirect evidence of decreasing average size of fish caught). The year 1950 marked the end of the major era of dogfish fishing when synthetic production of vitamin A became feasible and prices for dogfish crashed.
|Year||Type of gear||Total|
|Hook and line||Sunken gillnet|
The market driven crash of the vitamin A liver-oil fishery was followed by a long period of government-subsidised activity intended to revive the fishery and rid fishermen of what was perceived as a nuisance. As a result of substantial decreases in the catches after 1950, the stocks of dogfish recovered and by 1958 there were complaints that dogfish were eating baits and the catches of fishermen and destroying hooks and nets. The problem was acute in the south west coast of Vancouver Island and the Strait of Georgia and halibut fishermen were having the toughest times with dogfish interactions (Salsbury 1986). Several initiatives were taken by the government to introduce control measures and encourage a renewed fishery for dogfish. Some measures taken in 1959 under a special $Can500 000 grant included subsidies for liver oil, chartering trawlers in the Strait of Georgia to kill dogfish, buying livers from trawlers and longliners fishing anywhere along the coast, and paying subsidies to companies participating in the programme. An additional $Can150 000 was granted in 1960 and again in 1961 to continue subsidising purchases of livers. Most of the catches then were taken in the Strait of Georgia until abundance decreased and fishermen switched to the west coast of Vancouver Island. Although the government's initiative encouraged renewed interest in fishing for dogfish during those years, the programme showed no evidence of reducing dogfish abundance in the Strait of Georgia. The few CPUE statistics available show no decline, perhaps due to differences in year-to-year availability of dogfish. The “control” programme was followed in 1966 by a new initiative to develop a food-fish fishery for dogfish. An experimental marketing programme was launched with a $Can25 000 government grant. Landings of round dogfish received $60 and $40/t for longline and trawl-caught fish. A market survey identified potential markets in some European nations and dogfish products shipped during this trial were well received in most of these countries. Despite the experiment showing that a fishery could be developed if processing and shipping costs could be reduced, landings declined over the next six years. A further attempt to reduce dogfish numbers and develop a viable processing industry occurred in 1973. The $Can250 000 programme included roe herring catch bonuses for companies buying dogfish and focused on the Strait of Georgia where longline vessels took most of the catch followed by trawlers; also, some sunken gillnets were allowed under a special permit. The programme was successful in creating employment and spurring interest in dogfish among fishermen but failed as a marketing venture because of the short notice for implementation. The programme was extended in 1975 with an additional $Can50 000 to subsidise plants processing dogfish, but production fell again in 1975–76 (see Figure 7 and Table 3).
Ex-vessel prices for dogfish in current and 1986- constant dollars 1917–97. Data from Ketchen (1986), and Annual Summary British Columbia Commercial Catch Statistics, DFO Pacific Region (years 1973 to 1970)
2.1.3 Recent developments in the fishery
The present marginally successful food-fish fishery for dogfish started towards the end of the 1970s. Apparently, due to declines in the Scottish-Norwegian stock of dogfish and aggressive marketing by local entrepreneurs, European markets finally opened to dogfish from North America (Anon 1979, Ketchen 1986). The fishery for dogfish in the state of Washington was more successful to first capture a small part of the European market in 1975 and sharply boosted production in 1976. The BC fishery followed in Washington's footsteps in 1977. Since then, dogfish landings have been exported, in various forms, to several European and some Asian countries (Anon 1979, Salsbury 1986). Quality control for these markets requires prompt and diligent processing of dogfish. As a result, the fishery first relied heavily in longline vessels operating in the Strait of Georgia as processing plants receiving dogfish were more stable in the Vancouver-Seattle area. For a few years. there were efforts to develop the dogfish industry by opening more dogfish processing plants along the BC coast and expanding the fishing grounds to exploit the offshore stock. The number of plants involved in dogfish processing in BC increased from three in 1976 to eleven in 1980. According to Ketchen (1986), declining abundance in the Strait of Georgia stock coupled with financial problems (see Sec. 1.3.1) prevented the full development of the fishery in BC. Until present, a large proportion of the BC catches of dogfish are delivered directly or transshipped to US plants for processing (Table 4). The dependency on foreign processing plants and external markets makes for an unstable fishery and this is reflected in dogfish landings throughout this period. Since the late 1970s, landings have fluctuated around 3000t/yr with considerable variation (see Table 5). According to information from the BC Ministry of Food and Fisheries (J. Carson, BC MAFF, per. comm., Feb. 1998), during 1996 there were three main plants (from a total of eleven) processing dogfish in BC. Of the 24 plants processing skate, two major processors accounted for about 75% of the skate processed. A Polish joint venture fishery for dogfish using factory vessels and trawl gear was allowed to operate in 1977 but the fleet apparently took only about 450t of the 20 000t allocated. This fishery was not continued because of concerns over bycatches of rockfish and other species valuable to BC fishermen (Ketchen 1986, Salsbury 1986).
Historical catches of dogfish in BC. (a) top panel, total BC estimated catches (minimum and maximum estimates depend on conversion rate of parts to total weight of dogfish [see Ketchen 1986]) the five main phases in the history of the fishery are shown at the bottom of the figure; (b) middle panel, estimated catches for northern BC subareas; (c) bottom panel, estimated catches for southern BC subareas. Note that (b) and (c) do not always add up to (a) due to lack of spatial detail for some catches during certain periods. Data from Ketchen (1986). Thompson (1995) and Saunders (1997).
|Year||Queen Charlotte Islands||W. Coast Queen Charlotte Is||Hecate Strait||Queen Charlotte Sound||Strait of Georgia||W. Coast Vancouver Island||B.C. Total||Total Can+US|
Data for 1876–1916 from Ketchen (1986) table 3. Data for 1917–1939 from Ketchen (1986) table 4. Data for Hecate Strait 1940-1942 from Ketchen (1986) appendix 6. Data for Strait of Georgia 1940–1978 from Ketchen (1986) table 13. Data for BC total 1940–1978 from Ketchen (1986) table 12. Data for Hecate St., Queen Charlotte Sound, and WCVI for 1943–1953 from Ketchen (1986) table 15. Data for Hecate St., Queen Charlotte Sound, and WCVI for 1954–1961 from Ketchen (1986) table 17. Data for Hecate St., Queen Charlotte Sound, and WCVI for 1964–1975 from Ketchen (1986) table 19. Data for Hecate St., Queen Charlotte Sound, and WCVI for 1976–1978 from Ketchen (1986) table 23. Data for 1979 -onwards from Thomson (1995) and Saunders (1997): 1994–97 data are preliminary.
Management of the fishery through total allowable catch quotas (TAC's) has been in place at least since 1978 (Tyler 1988) but to date the fishery has never exceeded the TAC. For a number of years there were calls from industry for the reduction of dogfish populations due to gear and catch damage and alleged competition with fishermen for valuable fish species. The latter view was reinforced by Jones and Geen (1977) which suggestd that dogfish ate about 230 000t of herring/yr However, further research proved these figures to be overestimates (Ketchen 1986, Salsbury 1986). Because the fishery is marginally profitable and at the mercy of volatile markets, there has usually been a lack of suitable conditions for the expansion of the fishery; the development of new products and new markets in North America has been suggested as the only viable way to fully expand the fishery (Salsbury 1986). However, attempts to establish a successful and fully developed dogfish fishery will face two problems: dealing with high rates of bycatch of other species, and having a reliable and constant supply of dogfish that can sustain a stable market.
2.2 Evolution of catch
2.2.1 Overall catches
Ketchen (1986) estimated historical dogfish catches using the earliest records available by using conversion factors and statistics of liver, liver oil, body oil, mixed oil, and several body parts from dogfish. Because of uncertainty about the type of oil recorded in the historical statistics, he gave annual minimum and maximum estimates of dogfish catches for the period 1876–1939. Better reporting methods were used for the period 1940–82. Figure 7 shows the history of dogfish catches for BC (data in Table 3). The five major periods in the history of the fishery are easy to identify.
Dogfish catches at the beginning of the historical record were relatively high and comparable to the levels of the last 20 years. The low catch periods of the 1910s and 1960s are well marked, as are the outstanding catches during the boom vitamin A liver-oil fishery in the 1940s when over 31 000t were landed in BC in 1944. Two things are noteworthy: (1) the downturn of dogfish landings in 1993 was chiefly due to fire damage at one of the main processing companies in the Puget Sound area (Thomson 1995, Bonfil and Saunders 1997) and (2) the apparent increase in catches in 1996–97 might reflect improved information about discards rather than increased catches as the at-sea observer programme in the trawl fleet started in 1996.
The historical record presented in Figure 7 corresponds mostly to dogfish landings because discards in the different groundfish fisheries were not recorded until after 1979. Since then, the available statistics should be closer to actual removals of dogfish, although the total discards are still only partially documented. Discards in the hake fishery are known from logbook data only since 1986 but could also be inaccurate because of misreporting. The discards of dogfish in the halibut fishery remain unknown but could be significant given the complaints over the dogfish ‘nuisance’ among halibut fishermen (see Section 2.1.2). Given the importance of the dogfish industry in the last century and the first part of this century it is likely that prior to 1950 the landing data more closely represent the actual removals.
|Year||Fresh/whole dogfish||Total||Frozen/whole/dressed dogfish||Total||Grand total|
From 1979, it is possible to separate landing statistics from the component sources. The data presented for this period in Table 5 and Figure 7 correspond to the largest part of the total removals. These include statistics on landings, discards from the trawl fishery discards from the joint venture hake fishery and catches from the sport and shrimp bait fisheries. Only data on discards from the hook and line sector are missing. The estimated total catches of dogfish for the entire west coast of North America (including catches of the US fishery) are presented in Figure 8 and Table 3. The pattern of these catches follows that of the BC fishery demonstrating that the same market factors drove both fisheries. The maximum catch recorded in the history of the NE Pacific dogfish fishery was more than 50 000t landed in 1944 during the peak of the vitamin A liver-oil fishery. This peak catch can be used to bound values for the virgin biomass for stock assessments by use as a minimum value for B0 for all stocks of dogfish from Alaska to California, inclusive of the ‘coastal’ Strait of Georgia-Puget Sound stock.
|Year||Landings||Total landings||Total discards||Grand total|
Data for 1994–96 are preliminary
The large proportion of dogfish discards in the different groundfish fisheries of BC is poorly documented and difficult to estimate. Bycatch information has only been routinely collected for the trawl fishery since 1979 via logbooks, but the bycatch records from the trawl fishery are suspect because of severe misreporting which is well known among local fishermen and DFO personnel. Fishermen were known to group several species in the logbook records under a single name, or to not report fish dumped at sea. The suspicion of misreporting of dogfish catches in the past has been reinforced through inconsistencies found during modelling of the groundfish fishery (Walters and Bonfil 1997). This situation has improved considerably since the establishment of a mandatory 100% coverage at-sea observer programme for the trawl fishery (see Section 7.3). However, it is likely that large amounts of dogfish are dumped by the longline, especially by the talibut fishery, which are currently unaccounted for in stock assessment and management processes. The longlining fleet (with the exception of vessels fishing for rockfish) and the halibut fishery are not required to provide information on discards (logbooks are obligatory) and have no observers on board. This situation needs to be addressed if the dogfish fishery is to expand. At present, the only source of information of by catch of dogfish in the halibut fishery is the information held by the International Pacific Halibut Commission (IPHC) obtained through their yearly surveys (see Section 5.3.2).
Estimated total catches of dogfish in the Western North Pacific (Canada and U.S.) Data from Ketchen (1986), Thompson (1995) and Saunders (1997)
Discard data for the trawl fishery are available only for 1979–95 (Table 6), but there is a long period when discards were unaccounted for, and for which estimates are impossible. Quantities of dogfish may have been discarded by trawlers between the introduction of otter trawling (1903) and the beginning of the vitamin A fishery (1938), specially after 1933 when a sustained otter trawl fishery developed in the region (Alverson et al. 1964). Dogfish discards are expected to have been negligible or restricted to small fish during the years of the vitamin A fishery. Nevertheless, there is still a lack of information about trawl discards of dogfish since the collapse of the vitamin A fishery until about 1979 when trawl logbooks (on a voluntary basis) were instituted in the groundfish trawl fishery. The available data indicate that the proportions of discards and landings of dogfish vary considerably through the years. This might be due to changes in fishing patterns of the bottom trawl fishery and market constraints that limited the amount of dogfish that could be absorbed by the industry. Discards accounted for about 50% of the trawl dogfish catch up until 1986 but the rate of dumping increased sharply from 1987 and has only recently declined (Figure 5). This trend is mirrored in the amount of discards as proportion of the total catches of dogfish from all fisheries, although the pattern is less clear. Known discards exceeded 50% of estimated total catches of dogfish only in 1983 and 1992–94.
Most of the discards of dogfish occur on the west coast of Vancouver Island (areas 3C–3D). During 1979–94, 36% of the total discards were recorded in this region. Dogfish catches of the joint venture hake fishery - all of which are usually discarded - account for about 26% of the total discards. But this is an underestimate because there are no records of dogfish catches in the joint-venture hake fishery for the first half of this period. The Hecate Strait fishery accounts for 23% of the total discards, while Queen Charlotte Sound and the Strait of Georgia (the latter with bottom trawling severely restricted) contribute 12% and 4% of total discards respectively (see Table 6). Within each region, dogfish discard rates were proportionally higher in the Hecate Strait (72% discard rate), then in Queen Charlotte Sound (59%) and the west coast of Vancouver Island (34%), but were much lower in the Strait of Georgia (6%). More recently, better quality data for the trawl fishery were obtained through the at-sea observer programme. Preliminary total dogfish discard rates for the groundfish trawl fishery in 1996 (without considering the hake fishery) were estimated at about 95% (1650t).
|Year||WC Vancouver |
|St. of Georgia||QC Sound||Hecate St||Hake joint venture*|
L = Landings;
D = Discards
* All hake JV dogfish catches are discarded.
2.2.3 Catches by area
Ketchen was able to estimate catches in the major areas of the BC coast for a large part of the historical record (Figure 7, Table 3). Due to inadequate and changing reporting systems, fishing ground information was not always included in the landings reports. Thus, for some years it was impossible for Ketchen to allocate reported catches to specific geographical areas. Thus, some of the information of catches by area is incomplete and may only represent trends, or at best, minimum estimates of catches for each area; this is so for 1938–53 and 1962–63.
The information by area shows that dogfish fishing has traditionally been more important in the southern part of BC, specially in the Strait of Georgia. This is expected given the historical concentration of human settlements and processing facilities in southern BC. Until the late 1930s, most of the dogfish landings came from the Strait of Georgia although the Hecate Strait also played a role as a dogfish ground during the vitamin A liver-oil fishery. In recent years, the catch of dogfish in the Strait of Georgia has declined and the west coast of Vancouver Island has become the major fishing ground for dogfish, accounting for almost 50% of total catches for the period 1979–94.
2.2.4 Catches by gear
Throughout the history of the fishery most of the larger catches of dogfish have been made by the trawl fleet though the longline vessels delivered most of the landings in the later part of this century (Table 1). Trawl catches accounted for about 50% of the total BC dogfish catch (for which the gear is known) between 1943–59, while longlines accounted for about 10% during 1943–53 and for 27% during 1954–59. Sunken gillnets - now prohibited - accounted for 47% of dogfish landed in 1943–53. In the Strait of Georgia, 30% of the dogfish landed were caught with trawls, 68% with longlines and 3% with other gear (troll, trap, hand-lines) in 1972–82, a period when this area accounted for the largest part of BC's dogfish landings. During 1979–96, longlines have accounted for almost 60% of the landings of dogfish and 37% of the actual catches, while trawls took 60% of the catch but dumped half, thus accounting for only 37% of the landings. Other fishing gear accounted for 4% of the landings and 2.5% of the actual catch. As noted, the recent trend in gear used in the fishery is related to the export purpose of the fishery - human consumption. Table 5 shows that in the 1990s there was an increasing trend for most landings by longliners and lesser amounts by trawlers.
Dogfish landings in the last two decades are seasonal. There is a rather predictable pattern that seems to be independent of the gear used, but dependent on the fishing grounds. Data on quarterly landings by gear from the Strait of Georgia and the west coast of Vancouver Island for the years 1979–94 indicate larger landings during the first and mostly fourth quarters of the year in the Strait of Georgia (Table 7). Landings by both gears are larger in the first and mostly second quarters for the west coast of Vancouver Island. There is some detailed data available for catches of dogfish by gear and area. This information is presented in Table 8.
|Quarter||Strait of Georgia||W C Vancouver Is.|
2.2.5 Catches of other sharks and related species
In theory, dogfish is the only shark commercially exploited in BC as the experimental sixgill shark fishery was not allowed to develop into a commercial enterprise due to concerns over conservation. Several skate species are also landed as bycatch of the trawl and longline fisheries.
Table 8 presents data on the total landings and the landed and wholesale value of skates in BC since 1985. Skate landings have been variable and although there is an increase in landings over the period, they have never exceeded 1000t/yr. With the exception of the period 1986–88, the historical record shows yearly landings of less than 500t of skates until 1996–97 (first two years of reliable reporting through a 100% coverage at-sea observer programme) when catches (i.e. landings + discards) were estimated at 1293t and 1872t respectively (S. Spohn, DFO, per. comm., Dec. 1997). However, before this there was probably a large amount of discards that are not included in the statistics presented here. According to preliminary observer's data, about 1100t of skates were caught during 1996 in the operations of the groundfish trawl fishery but half were discarded at sea. The most commonly harvested species of skates are big skate, long-nose skate, and deep-sea skate. However, about 25% of the catch is reported only as “skates”. Landings records pertain mainly to “skates”, big skate and longnose skate (Table 9 and 10).
LL = longline,
HL&T = hand lines and troll,
Land. = landings.
Every year, small amounts of other sharks are caught and occasionally landed. Soupfin sharks, salmon sharks, blue sharks, sleeper sharks and sixgill sharks are the most common apart from an item called “sharks” in the statistics. However, the landings of “sharks” are small (8.7t and 0.3t in 1996 and 1997 respectively) and are not discussed further here.