3. REPORT ON THE SPINY LOBSTER FISHERY OF BERMUDA

Tammy Trott^[12], Brian E. Luckhurst and Paul Medley

Description of the Fishery

Since the establishment of the permanent, limited entry fishery for Panulirus argus in 1996 (see Luckhurst, 2001), the level of participation, trap allotments and terms for the inshore fishery have varied but within a relatively narrow range (Table 1). While the number of participants ranged from 16 in the first year to a high of 27 in the 2000/2001 season, the total trap allotment for the fishery has only varied by 60 traps (range 270-330 traps) over the six years. All traps are owned by the government and are leased to licence holders on an annual basis.

Table 1. Summary of participation and trap allocations for the P. argus fishery in Bermuda between 1996 and 2002

Traps may only be set in the two designated inshore areas (Fig. 1) for a four-month period during the winter (December-March). The central section of the Bermuda reef platform is maintained as a reservoir where no commercial lobster fishing is permitted.

A recreational lobster diver programme was established in 1984 (Luckhurst, 2001). The number of licences issued during the past 6 years has ranged from 450 to 581.

In 1998, an experimental fishery targeting the spotted spiny lobster, Panulirus guttatus, was launched with a view to re-establishing a commercial fishery for this species (which was curtailed in 1990 due to the fish pot ban). Historically, only a small number of fishers have participated in the spotted spiny lobster fishery, but over the years a strong local market has become established for this species (Luckhurst et al., 2001b).

Figura 1. Map showing the two designated inshore spiny lobster (Panulirus argus) fishing areas in Bermuda

The experimental P. guttatus fishery commenced with four license holders and tested two basic trap types, a wire mesh trap constructed by the former Division of Fisheries and a plastic, commercially built crustacean trap. Based on analysis of data collected during the first two years of the experimental fishery, the plastic trap has been recommended for exclusive use when a commercial fishery is implemented (Luckhurst et al., 2001b).

Management Regulations

The following management regulations are in place for P. argus in Bermuda.

• It is illegal to harvest or be in possession of lobsters:

  - less than 92 mm (3.6 in) carapace length;
  - during the closed season: April 1 to August 31; with eggs;
  - using any gear type other than that for which the fisher is licensed: commercial-standard traps only, recreational-lobster noose only.

• It is illegal to wring lobster tails at sea, therefore, all lobsters must be landed whole.

• Recreational lobster divers may only take two lobsters per day.

• Area restrictions apply to both commercial and recreational fishers, however, former spatial separation between these two user groups is no longer maintained.

• Imported lobsters are inspected for compliance with regulations. Lobster tails must have a minimum weight of 336 g (12 oz).

Both commercial and recreational fishers are required to submit catch and effort statistics for each fishing trip. There is, however, no systematic validation of the accuracy of the data provided from this self-reporting system.

Biology

The tagging programme for P. argus, initiated in 1997 (Luckhurst, 2001), is still ongoing. To date 676 lobsters have been tagged and there have been 67 recaptures. Data analysed thus far shows that lobsters are capable of long distance travel, although their movement patterns are highly variable (Luckhurst et al., 2002). The longest distance (point-to-point) moved by a recaptured lobster was 45.9 km and the average distance travelled by all recaptured lobsters was 12.2 (± 11.4 SD) km. Days at liberty ranged from 9-700 days with a mean value of 294 (± 168 SD) days. From this preliminary analysis, it was concluded that lobster movements are probably adequate to replenish the two designated commercial inshore areas at the present levels of fishing effort.

Available Data and Recent Developments

Landings of P. argus have varied during the past six years from a record year in the 1999/2000 season of 36 515 lobsters to a low of 17 393 lobsters this past 2001/02 season (Fig. 2). The highest landings figure previously recorded was 35 193 lobsters in 1989 (before the fish pot ban of 1990). It is not possible, however, to directly compare this figure with lobster landings taken during the limited entry fishery as there are no acceptable measures of directed fishing effort for lobsters before the fish pot ban.

Figure 2. Reported lobster (Panulirus argus) landings from the commercial fishery and recreational divers in Bermuda

Recreational diver lobster landings have varied from 3 517 lobsters to 1 196 between the 1996/97 and 2000/01 seasons (see Fig. 2). A landings figure is not yet available for the 2001/2002 season.

The CPUE (catch per unit effort) from 1996-2001 has been relatively stable for the offshore fishery with a peak occurring in 1999. In contrast, the inshore CPUE has shown a declining trend with a substantial drop in the 2000/01 season (Fig. 3). Used as a proxy for abundance, this drop in CPUE suggests a reduction in population abundance in the inshore areas. Due to the uncertainty regarding the factors responsible for the substantial decline in landings and CPUE for the 2000/2001 season, a precautionary management approach was adopted and fishing effort was reduced for the 2001/2002 season (see Table 1). Although, the total landings for the past season (2001/2002) were down from the previous year, the CPUE was considerably higher (see Fig. 3).

Size-frequency distributions for lobsters caught offshore and inshore suggest a fairly stable population size structure as there have been few changes in modal values over time.

Figure 3. Mean CPUE figures for the Offshore and Inshore P. argus fishery in Bermuda

Mean CPUE for the Offshore Fishery

Mean CPUE for the Inshore Fishery

In the first year of the experimental P. guttatus fishery, a total of 10 592 lobsters were caught and 9 206 lobsters were landed in the second year. During the period before the fish pot ban (1975-1989), landings figures ranged between about 13 000 to almost 42 000 spotted spiny lobsters (Luckhurst et al., 2001b).

Status of the National Spiny Lobster Resource

Stock assessment: Depletion model

A depletion model was fitted to the weekly CPUE for each of the six years of the limited- entry spiny lobster fishery. A simple population model was used to estimate expected catches based on the catch removals:

The population model is the same as that used in a previous FAO workshop (FAO, 2001). Also, the method estimates fishing mortality directly and can be compared with fishing mortality reference points. For example, the natural mortality could be used as a limit reference point, so that the number of hauls in a season could be limited to the point where F = 0.35 year^-1.

The model was fitted by minimising the sum of squared differences between the square-root transformed observed and expected catches. Also, all years were fitted simultaneously with the same catchability parameter, but the initial population fitted to each year.

Figure 4. Observed and expected catch per trap haul for the inshore fishery from 1996-2001.The size of each sharp increment represents the estimated recruitment after allowing for natural mortality (Table 2)

The model fitted the data well (R² = 0.78), describing the main trends in changes of CPUE (Fig. 4). The model fitted less well than when allowing catchability to change, but the final estimate of catchability used for management purposes will be more accurate as an estimate of the expected catchability per haul.

Table 2. The lobster resource in the inshore areas shows an overall decline since it reopened in 1996. While effort has been largely controlled, the heavily exploited state of the stock is a direct result of the recruitment failures in 1997 and 2000

The implication for management of this resource is that as recruitment cannot be guaranteed in all years, fishing mortality needs to be limited to allow adequate escapement to ensure depletion does not occur in years when recruitment is poor. Such depletion has occurred in 2000, suggesting fishing was too high in the period 1997-2000. One solution might be to close the season early when insufficient recruitment is detected at the beginning of the season. The mechanism of how to do this would have to be decided.

Figure 5. Estimated fishing mortality as measured against a suggested precautionary reference point (the regional estimate for natural mortality; FAO, 2001)

The sequential years show an interesting pattern. The years show either a discrete recovery or continued decline between years. The pattern is remarkably consistent (Table 2). The increases between years are recruitments to the area being exploited. However, it is clear such recruitments are not repeated in all years, and recruitment failures can be clearly seen in the time series. The degree to which this pattern is driven by recruitment can be verified by looking at the lobster size frequencies in sequential years.

Since the start of the limited entry fishery in 1996, active monitoring of all aspects of the fishery has increased. This has provided good quality data for use in the active management of the fishery. Annual assessment of these data sets permits adaptive management of the fishery, which seeks to maintain a sustainable harvest in an economically efficient manner.

Effort has declined, probably due to recruitment failure and subsequent poor catch rates in 2000. Recruitment did occur in 2001, so that the fishery has recovered somewhat. However, it is apparent that increased effort attracted to the fishery since the inshore fishery reopened pushed the fishing above desirable levels (Fig. 5), and probably caused the overfishing in 2000. Avoiding fluctuations in catch rates and catches will require more effective fishing effort control.

Social and Economic Status and Importance of the Fishery

Spiny lobsters are sold in Bermuda according to size as opposed to weight. Most of the larger lobsters (> 5 mm CL) are sold directly to customers from fishers at roadside vending stands. Prices for these lobsters range from US$25 to US$35. The smaller lobsters (< 115 mm CL) are usually sold to local restaurants and hotels for approximately US$20. The estimated values of spiny lobster landings, summarized in Table 3, are based on size frequency distribution data collected in each year.

Table 3. Summary of commercial spiny lobster (P. argus) landings in weight and value

The lobster fishery in Bermuda is a supplementary fishery, however, it is very important to the participants as it provides an additional source of income especially during the winter months. During the period December-March, finfish catches are generally lower due to reduced effort as a result of inclement weather. In addition, the abundance of key fishery species such as wahoo (Acanthocybium solandri) and yellowfin tuna (Thunnus albacares) is typically low during the winter months (Luckhurst and Trott, 2000; Luckhurst et al., 2001a) thus reducing the fishers's potential income. As a result, participation by commercial fishers in the lobster fisheries forms a significant part of their annual fishing activities.

Recommendations

• Develop and declare precautionary and limit reference point (F_pa, F_max). Such reference points may require further research, but ultimately must be chosen by the decision-makers to represent their attitude to risk in managing the resource. Note, if fishing mortality is unacceptable, other indicators/reference points are available, such as those based on catch or mean catch-per-haul.

• Control effort (or other suitable variable) based on the indicator and reference points. For example, the end of season could be based on cumulative number of hauls rather than a fixed date or the season could be closed at a fixed early date based on whether or not recruitment failure was detected.

• Continue to monitor the population and estimate recruitment. The time series of catches and hauls will prove a valuable tool in developing new population dynamics models for this species. Bermuda is relatively isolated, so that it may be easier to identify where recruits are coming from and develop an accurate population model including terms for larval immigration if necessary.

References

FAO. 2001. Report on the FAO/DANIDA/CFRAMP/WECAFC Regional Workshops on the Assessment of the Caribbean Spiny Lobster (Panulirus argus). Belize City, Belize, 21 April-2 May 1997 and Mérida, Yucatán, México, 1-12 June 1998. FAO Fisheries Report No. 619. FAO, Rome, 381 p.

Luckhurst, B.E. 2001. National report on the spiny lobster fishery in Bermuda. FAO Fisheries Report No. 619: 175-178.

Luckhurst, B.E. & Trott, T. 2000. Bermuda's commercial line fishery for wahoo and dolphinfish: landings, seasonality and catch per unit effort trends. Gulf. Carib. Fish. Inst. 51: 404-413.

Luckhurst, B.E.; Trott, T. & Manuel, S. 2001a. Landings, seasonality, catch per unit effort, and tag-recapture results of yellowfin tuna and blackfin tuna at Bermuda. pp. 225-233 In: G.R. Sedberry (ed.). Island in the stream: oceanography and fisheries of the Charleston Bump. American Fisheries Society, Symposium 25, Bethesda, Maryland.

Luckhurst, B.E.; Trott, T. & Manuel, S. 2001b. Preliminary results from an experimental trap fishery for the spotted spiny lobster, Panulirus guttatus, in Bermuda. Gulf. Carib. Fish. Inst. 52: 222-230.

Luckhurst, B.E.; Trott, T.; Simmons, N. & Manuel, S. 2002. Movement patterns of tagged spiny lobsters Panulirus argus on the Bermuda reef platform. Gulf. Carib. Fish. Inst. 53: 76-82.

DECISION-MAKING MECHANISM FOR FISHERIES MANAGEMENT REGULATIONS IN BERMUDA