Inshore Gulf of Maine Rock Crab (Cancer Irroratus)
Fisheries Pêches and Oceans et Océans DFO Science Maritimes Region Stock Status Report C3-67(2000)
Inshore Gulf of Maine Rock Crab (Cancer irroratus) Summary • Commercial concentrations of rock crabs Background were found in only a few specific areas: Rock crab (Cancer irroratus) have a broad, oval In St. Marys Bay (LFA 34), in Annapolis carapace with nine smooth teeth along the margin of Basin (LFA 35) and in southwestern each side. They concentrate in shallow water less New Brunswick (LFA 36). than 20 m deep and prefer sandy bottom, although • Removals of rock crab as a bycatch in they can be found on all types of substrate. Molting occurs primarily in April and May and earliest the lobster fishery are currently maturity is around 25 mm and 40 mm carapace width underreported but in LFA 34 & 35 (CW) for females and males respectively. Average landings statistics have shown that maturity occurs between 50 mm and 57 mm for bycatch of rock crab surpassed landings females while average male maturity is between 65 from the directed fishery in 1999. Until mm and 75 mm CW. Egg extrusion appears to occur in late October with development of six larval stages the quantity of rock crab removals by the occurring the following summer. Males reach a lobster fishery is better documented, larger size than females with a maximum carapace biological sustainability of the directed width of 150 mm and 110 mm respectively. fishery cannot be evaluated. Commercial size is reached in approximately 6 years. • Risks of overfishing of rock crab by the Inshore Gulf of Maine exploratory rock and Jonah directed fishery are low given current crab fisheries were initiated in southwest New effort levels and the high protection for Brunswick (Lobster Fishing Areas, LFA’s 36 & 38) in broodstock provided by minimum size 1995 and in southwest Nova Scotia (LFA's’34 & 35) regulation. in 1996. Two Developing Species Advisory Boards • (DSAB’s) were created to manage these new crab Based on logbook analysis, annual catch fisheries as well as other developing fisheries. One rates were higher in Annapolis Basin was initiated in southwest New Brunswick in 1995 (from 5.6 to 8.1 kg per trap haul (kg/th)) and the other in southwest Nova Scotia in 1996. The compared to St. Marys Bay (from 1.7 to crab permits were distributed by Lobster Fishing 4.3 kg/th) and southwest New Areas (LFA’s).
March 2000 Maritimes Region Inshore Gulf of Maine Rock Crab
Brunswick (from 2.3 to 3.5 kg/th). Data In LFA’s 36 & 38, exploratory crab permit collected to date is insufficient to detect holders were allowed to land rock and Jonah trends. crab. The minimum size limit for male rock • Based on at-sea sampling of trap crab was set at 102 mm CW. The trap limit contents, monthly mean size of males was set at 200 in LFA 36 and 300 in LFA and females were similar in all areas and 38, Only conical traps were allowed, and between years. The percentage of berried were required to have a minimum of two females in the traps was low (<2 %). circular openings of 63.5 mm (2 ½”) in • Lobster by-catch, as reported in diameter. Also the crab-fishing season is logbooks from the inshore rock crab open all year. For participants to retain their fishery, was a problem in St. Marys Bay exploratory fishing permits, they were (LFA 34) and Annapolis Basin (LFA required to complete 15 fishing trips and had 35), during 1996 and 1997. However, to land at least 30 % of average landings (in generally low numbers of lobsters per weight) of all fishers within a given year for trap haul were reported during 1999 (< their respective LFA. 0.01). In limited sea sampling in St. Marys Bay and Annapolis Basin (4 Distribution of rock crab fishing locations as reported in fishers’ logbooks. samples), the number of lobster per trap haul was 0.1 and 0.4 compared to 0.2 and 2.0 in 1996, respectively.
The Fishery
Evolving from two separate Developing Species Advisory Boards (DSAB’s), the present management regime has various regulations. Presently, in LFA’s 34 and 35 participants are allowed to land rock crab only. The minimum size limit for male rock crab was set at 102 mm CW. Modified lobster traps were permitted to be used as The exploratory rock crab fishery, in well as conical crab traps, with a trap limit operation since 1995, has located several of 150. Traps were to include a minimum of commercial concentrations: St. Marys Bay two escape gaps of a minimum diameter of (LFA 34); Annapolis Basin (LFA 35); along 63.5 mm (2.5 inches). They were only the New Brunswick coast in the Maces Bay allowed to begin fishing for crab one week area and around the Fundy Isles (LFA 36). after the closure of the spring lobster fishing Rock crabs were mostly found in shallow season, and had to remove their traps one waters near the coast. week before the opening of the fall lobster fishing season. In order for participants to Resource Status retain their exploratory permits, they had to land and sell a minimum of 5,000 kg of rock There are no fishery-independent surveys for crab. this species, and this assessment is based on catch rates and size composition data from
2 Maritimes Region Inshore Gulf of Maine Rock Crab the commercial catch. Traps are highly Rock Crab Catch Rate and Effort (LFA 34, 1996-99) selective, and crustacean catchability is 8000 12 (TH) 10 6000 affected by a variety of factors. The catch (Kg/TH) 8 rate data have not been standardized for 4000 6 4 2000 Kg. per Trap Hauls fisher, trap type, area and season, and No. of Trap Hauls 2 standardization would be difficult because 0 0 Jul-96 Jul-97 Jul-98 Jul-99 Oct-96 Oct-97 Oct-98 Oct-99 Jun-96 Jun-97 Jun-98 Jun-99 Sep-96 Sep-97 Sep-98 Sep-99 Aug-96 Aug-97 Aug-98 Aug-99 the important variables are available for only Monthly Periods a small subset of the data. Some of the variation in the catch rate and size In Annapolis Basin (LFA 35), landings composition probably results from factors peaked in 1997 at 45.5 t. Preliminary other than the abundance of rock crab. landings in 1999 show a decline to 13.6 t. However the yearly average catch rate has In all LFA’s most of the fishing took place remained at higher levels (varied between between June and the end of October even 5.6 and 8.1 kg/th) than all other areas. when the crab season was open all year as in Monthly average catch rates show a decline LFA 36. between August to September of each year.
Rock Crab Catch Rate and Effort (LFA 35, 1996-99) Rock Crab 1995 1996 1997 1998 1999 8000 12 LFA 34 Trap Hauls 8558 13916 3000 5451 (TH) (St. Marys Landings (t) 36.7 33.5 5.0 16.1 10 6000 (Kg/TH) Bay) Mean CPUE 4.3 2.4 1.7 3.0 8 No. of Logbooks 2 2 2 2 4000 6 By-catch (t) ** ** 48 33 4 LFA 35 Trap Hauls 2618 6445 4235 1685 2000
No. of Trap Hauls 2 (Annapolis Landings (t) 19.1 45.5 23.7 13.6 Kg. per Trap Hauls Basin) Mean CPUE 7.3 7.1 5.6 8.1 0 0 No. of Logbooks 3 4 2 2 By-catch (t) ** ** 13 26 Jul-99 Jul-98 Jul-97 Oct-99 Oct-98 Oct-97 Oct-96 Sep-99 Sep-98 Sep-97 Sep-96 Aug-99 Aug-98 Aug-97 LFA 36 Trap Hauls 7383 6103 2608 14696 10748 Aug-96 Landings (t) 22.8 16.3 9.1 37.1 24.3 Monthly Periods Mean CPUE 3.1 2.7 3.5 2.5 2.3 No. of Logbooks 4 4 2 6 5 By-catch (t) ** ** ** 0 23 In southwestern New Brunswick (LFA 36), LFA 38 Trap Hauls 2023 Landings (kg) 1938 landings obtained from logbooks from the Mean CPUE 1.0 No. of Logbooks 1 original four permit holders decreased from By-catch (t) ** ** ** 0.9 5.7 ** Unknown 22.8 t in 1995 to 9.1 t in 1997. After the replacement of inactive permits, and In St. Marys Bay (LFA 34), two crab fishers allocation of four new permits, landings have been fishing for rock crab since 1996. increased to 37.1 t in 1998 and preliminary Rock crab landings obtained from logbooks landings were 24.3 t in 1999. Yearly average peaked the first year (1996) at 36.7 t and catch rate for 1998 and 1999 varied between subsequently declined to 5 t in 1998 and 2.5 to 2.3 kg/th with the increase of effort were up at 16.1 t in 1999. Since 1996, yearly during 1998 and 1999. Monthly average average catch rate in kg per trap haul (kg/th) catch rates show no seasonal trends. varied between 1.7 and 4.3. Monthly average Rock Crab Catch Rate and Effort (LFA 36, 1995-99) catch rates varied between months and no 8000 12 (TH) 10 6000 (Kg/TH) seasonal trend was noticeable. 8 4000 6 4 2000 No. of Trap Hauls
2 Kg. per Trap Hauls 0 0 Jul-99 Jul-96 Oct-98 Oct-97 Oct-95 Apr-95 Jun-98 Jun-95 Sep-99 Sep-96 Aug-98 Aug-97 Aug-95 Monthly Periods Yearly average catch rates were similar in LFA’s 34 and 36 despite the fact that
3 Maritimes Region Inshore Gulf of Maine Rock Crab different trap types were used (1.7 to 4.3 minimum legal size of 102 mm CW was kg/th). However yearly average catch rate in also lower in Passamaquoddy Bay (0.3%) Annapolis Basin (5.6 to 8.1 kg/th) was compared to the samples taken along the higher than in the other two LFA’s. New Brunswick coast (5 to 7 %). The mean size of females was larger in At-sea sampling provides detailed Passamaquoddy Bay (103 mm CW) information on crab size structure in the compared to the area along the N.B. coast traps. All crabs retained in individual trap (86 and 95 mm CW). The percentage of hauls are measured, and examined to berried females was less than 2 %. determine species, sex, molt condition and egg development stage for berried crabs. As LFA 34 (St. Mary's Bay) Sept 1996, Rock Crab the exploratory rock/Jonah crab fisheries 80 70 Males were evolving in the various LFA’s, 60 Females N= 305 50 N= 297 Mean= 121 mm CW emphasis was placed in sampling a series of Mean= 93 mm CW SD= 11.6 40 SD= 4.0 5 % < 102 mm CW representative ports in areas and at time 30 20 periods when high fishing activity occurred. No. of Rock Crabs 10 0 All the sampling occurred during July, 60 70 80 90 100 110 120 130 140 150 August and September. In some instances, Carapace Width (mm) when several samples were taken during the LFA 34 (St. Mary's Bay) August 1999, Rock Crab same month in the same location, the 80 70 Males samples were combined into one monthly 60 N = 423 Females Mean = 118 mm CW 50 sample. N = 146 SD = 11.1 40 Mean = 93 mm CW 8 % < 102 mm CW SD = 4.9 30 20 In LFA 34 (St. Marys Bay) and LFA 35 No. of Rock Crabs 10 (Annapolis Basin), rock crab at-sea samples 0 60 70 80 90 100 110 120 130 140 150 were obtained during September 1996 and Carapace Width (mm) August 1999, respectively. The average size of males was greater in St. Marys Bay (121 LFA 35 (Annapolis Basin) Sept. 1996, Rock Crab 80 and 118 mm CW) compared to Annapolis 70 Males 60 Basin (111 and 113 mm CW). The Females N = 290 50 N =119 Mean = 113 mm CW percentage of males below the legal size 40 Mean = 90 mm CW SD = 11.5 limit of 102 mm CW was less in St. Marys 30 SD = 5.7 13.8 % < 102 mm CW 20 No. of Rock Crabs Bay (5 and 8 %) compared to Annapolis 10 Basin (14 and 20 %). The mean size of 0 60 70 80 90 100 110 120 130 140 150 females was higher in St. Marys Bay (93 Carapace Width (mm) mm CW) compared to Annapolis Basin (89 and 90 mm CW). The percentage of berried LFA 35 (Annapolis Basin) August 1999, Rock Crab 80 females was less than 1 % in both areas. 70 60 Females Males 50 N =175 N = 550 LFA 36 was sampled in July 1995 and in Mean = 89 mm CW Mean = 111 mm CW 40 SD = 5.1 SD= 10.7 August and September 1999. The mean size 30 20% < 102 mm CW 20 No. of Rock Crabs of males was greater in Passamaquoddy Bay 10 (122 mm) compared to the samples along 0 the New Brunswick shore (113 and 118 60 70 80 90 100 110 120 130 140 150 Carapace Width (mm) mm). The percentage of males below the
4 Maritimes Region Inshore Gulf of Maine Rock Crab
mean sizes of rock crabs were similar in all In LFA 38, one rock crab sample was taken areas. during August 1995 before fishing effort was diverted to Jonah crab fishing. The Lobster bycatch has been a management mean size of males was 113 and 83 mm CW concern since the inception of the for females. exploratory crab fishery. However, restrictions on the type of traps used and
LFA 36 (Beaver & Maces Bay) July 1995, Rock Crab limitations on the size and shape of the 80 Males entrances, seem to have reduced the 70 N = 1305 60 Mean = 118 mm CW incidence of lobster bycatch. Yearly average SD = 10 50 Female 5 % < 102 mm CW number of lobster per trap haul (lob./th), as 40 N = 267 Mean = 86 mm CW 30 reported in logbooks was higher in St. Marys SD = 6.8 20 Bay (LFA 34) (0.3 and 0.5 lob./th) and No. of Rock Crabs 10 0 Annapolis Basin (LFA 35) (0.08 and 0.04 60 70 80 90 100 110 120 130 140 150 lob./th) during 1996 and 1997. However, on Carapace Width (mm) average low numbers of lobsters per trap LFA 36 (Maces Bay) August 1999, Rock Crab haul were reported during 1999 (< 0.01). 80 70 Limited sea sampling in St. Marys Bay and Males 60 N = 501 Annapolis Basin (4 samples) has shown that 50 Females Mean = 113 mm CW 40 N = 38 7 % < 102 mm CW in 1999, the number of lobster per trap haul Mean = 95 mm CW 30 SD = 6.1 was 0.1 and 0.4 compared to 0.2 and 2.0 in 20 No. of Rock Crabs 10 1996, respectively. In LFA’s 35 and 36 the 0 monthly average number of lobsters per trap 60 70 80 90 100 110 120 130 140 150 Carapace Width (mm) haul, as reported from logbooks, has been low (< 0.3). Limited sea sampling in 1999 LFA 36 (Passamaquoddy Bay) Sept. 1999, Rock Crab 80 indicates that the number of lobsters per trap 70 Males haul was 0.07 compared to 0.0 in 1995. 60 N = 363 50 Females Mean = 122 mm CW 40 N = 49 SD = 8.5 Lobster Bycatch (LFA 34, St. Marys Bay, 1996-99) 0.3 % < 102 mm CW 30 Mean = 103 mm CW SD = 4.3 3.0 20 2.5 No. of Rock Crabs 10 2.0 0 1.5 60 70 80 90 100 110 120 130 140 150 1.0 Carapace Width (mm) 0.5
No. of Lob./Trap Hauls 0.0
LFA 38, August 1995, Rock Crab Jul-99 Jul-98 Jul-97 Jul-96 Oct-99 Oct-98 Oct-97 Oct-96 Jun-99 Jun-98 Jun-97 Jun-96 Sep-99 Sep-98 Sep-97 Sep-96 Aug-99 Aug-98 Aug-97 Aug-96 80 Males Monthly Periods 70 N = 814 Mean = 113 mm CW 60 Lobster Bycatch (LFA 35, Annapolis Basin, 1996-99) SD = 6.8 3.0 50 Females 4% < 102 mm CW 2.5 40 N = 21 Mean = 83 mm CW 2.0 30 SD = 7.5 1.5 20 1.0
Number of Rock Crabs 10 0.5
0 No. of Lob./Trap Hauls 0.0 60 70 80 90 100 110 120 130 140 150 Carapace Width (mm) Jul-97 Jul-98 Jul-99 Oct-96 Oct-97 Oct-98 Oct-99 Sep-96 Sep-97 Sep-98 Sep-99 Aug-96 Aug-97 Aug-98 Aug-99 Overall, although different trap types were Monthly Periods used in LFA’s 34 & 35 (modified lobster traps) and LFA’s 36 & 38 (conical traps) the
5 Maritimes Region Inshore Gulf of Maine Rock Crab
Lobster Bycatch (LFA 36, 1995-99) fishery is marginal and very dependent on 3.0 the value and the demand for the product. 2.5
2.0 1.5 Removals of rock crab by the lobster fishery 1.0 as a bycatch, are currently underestimated 0.5 No. of Lob./Trap Hauls 0.0 and under no limitation. Reported landing statistics shows that rock crab landings as a Jul-96 Jul-99 Apr-95 Oct-95 Oct-97 Oct-98 Jun-95 Jun-98 Sep-96 Sep-99 Aug-95 Aug-97 Aug-98 Monthly Periods bycatch to the lobster fishery in LFA 34 & Sources of Uncertainty 35 have surpassed the directed fishery in 1999. Until the quantity of rock crab Total removals of rock crab in the Gulf of removals by the lobster fishery has been Maine are not known because the bycatch of further evaluated, biological sustainability of rock crab by the lobster fishery is not well the directed fishery cannot be evaluated. documented. Anecdotal evidence indicates few rock crab are retained by lobster fishers Other Considerations in some areas (e.g. LFA 38) but in other areas lobster traps are set specifically for Smaller rock crabs are an important rock crab to be used as bait or sold. component of the diets of lobster and some Reported landings in LFA’s 34 and 35 have inshore groundfish. The directed fishery shown that bycatch of rock crabs surpassed focuses on larger crabs that are not as landings from the directed fishery in 1999, important as a food source. Thus the effect and could increase or decrease in response to of rock crab removals on the production of economic factors. lobsters and other species is likely negligible as long as small rock crab are not harvested, Outlook and removals are below the level at which overfishing occurs. There is still some room for limited expansion in unexplored areas in LFA 34 The rock crab fishery is male only (as are all and especially in LFA 38 where rock crab Canadian crab fisheries), and there are some were initially found in 1995 but ignored as concerns that this could limit future egg effort was directed at the more lucrative production if large males are needed to mate Jonah crab. In LFA 35 & 36 it is unlikely females. More research in this area is that commercial concentrations of rock crab needed. will be located in the upper part of the Bay of Fundy. There is still some possibility of Management Considerations moderate expansion around the Fundy Isles in LFA 36. The current level of effort does Rock crabs are fished by a directed fishery not appear to be having any obvious impact and as a bycatch in the lobster fishery. The on the resource such as a reduction in potential effort by the lobster fishery is far average catch size or reduction in catch greater than the directed fishery. Removals by rates. Risks of overfishing of rock crab by the lobster fishery are a fundamental piece of the directed fishery are low given current missing information needed for the effort levels and the high protection for assessment of rock crab stock(s). Until the broodstock provided by minimum size quantity of rock crab removals by the lobster regulation. The economic feasibility of this fishery is evaluated and controlled, biological
6 Maritimes Region Inshore Gulf of Maine Rock Crab sustainability of the directed fishery cannot be Fishing Areas 34, 35, 36 & 38. DFO evaluated. The bycatch issue should be Can. Stock Assess. Sec. Res. Doc. looked at on an LFA by LFA basis since in 2000/051. some LFA’s these issues could be more easily resolved than in others. Lobster fishermen should be encouraged to report their bycatch whether it is used directly as bait or sold.
As far as the directed fishery is concerned, management provisions should remain flexible to reflect the developing nature of the fishery. More work needs to be done on evaluating trap designs that limit lobster bycatch before more stringent trap specifications are added to the regulations.
To better evaluate the potential for rock crab directed fishery, more fishing effort (e.g. increased participation rates, additional permits or additional traps) should be targeted to lightly fished areas.
For more Information
Contact: David Robichaud or Peter Lawton Fisheries & Oceans Biological Station 531 Brandy Cove Rd. St. Andrews N.B. E5B 2L9
Tel: (506) 529-8854 Fax: (506) 529-5862 E-Mail: [email protected] or [email protected]
References
Robichaud, D. A. and P Lawton, 2000. Exploratory Fisheries for Rock Crab, Cancer irroratus, and Jonah Crab Cancer borealis, in Canadian Lobster
7 Maritimes Region Inshore Gulf of Maine Rock Crab
This report is available from the:
Maritimes Provinces Regional Advisory Process Department of Fisheries and Oceans P.O. Box 1006, Stn. B203 Dartmouth, Nova Scotia Canada B2Y 4A2 Phone number: 902-426-7070 e-mail address: [email protected]
Internet address: www.dfo-mpo.gc.ca/csas ISSN: 1480-4913
La version française est disponible à l’adresse ci-dessus.
Correct citation for this publication
DFO, 2000. Inshore Gulf of Maine Rock Crab (Cancer irroratus). DFO Science Stock Status Report C3-67(2000).
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