Not to be cited without

Ne pas citer sanspermission of the author( ) l

autorisation des au - _ur (s) 1

Canadian Atlantic Fisheries Comite scientifique consultatif desScientific Advisory Committee peches canadiennes dans I'Atlantique

CAFSAC Research Document 88/12

CSCPCA Document de recherche 88/ 12

Scotia-Fundy Shrimp Stock Status - 1987

by

M.L. Etter and R.K. MohnHalifax Fisheries Research Laboratory

Biological Sciences BranchDepartment of Fisheries and Oceans

Scotia-Fundy RegionP.O. Box 550Halifax, N.S.

B3J 2S7

'This series documents the scientificbasis for fisheries management advicein Atlantic Canada. As such, itaddresses the issues of the day inthe time frames required and theResearch Documents it contains arenot intended as definitivestatements on the subjects addressedbut rather as progress reports onongoing investigations.

Research Documents are produced inthe official language in which theyare provided to the Secretariat bythe author(s).

1Cette serie documente les basesscientifiques des conseils degestion des p@ches sur la coteatlantique du Canada. Commetelle elle couvre les problemesactuels selon les echeanciersvoulus et ales Documents derecherche qu'elle contient nedoivent pas etre considerescomme des enonces finals sur lessujets traites mais plutot commedes rapports d'etape sur lesetudes en cours.

Les Documents de recherche sontpublies dans la langueofficielle utilisee par lesauteur(s) dans le manuscrit—envoye au secretariat.

2

Abstract

The Scotia-Fundy shrimp (Pandalus borealis) fishery covers threeareas with depths > 100 fm, referred to as Canso, Louisbourg, andMisaine holes. These areas have been continuously underexploited overthe past years, as in 1987 only 152 t (7.1%) of the total quota of 2140t were taken. This represents an exploitation rate of 2.0% based on thetotal biomass estimate (Etter and Mohn, 1987).

Effort was low again this year with seven boats reporting catches.Of these, three were from New Brunswick (>65 ft) and accounted for about91% of the total catch. Of the total, 148 t was taken from theLouisbourg area which was 13.8% of the Louisbourg quota of 1070 t. Theremaining 4 t was caught in Misaine with no catches reported in Canso.The other four boats involved in the fishery were Cape Breton basedvessels (<65 ft). The fleet fished mainly with the Sputnik and Yankee 41shrimp trawls with a regulation 40 mm mesh size. This fishery isseriously affected by a 10% by-catch limit which is difficult to attainin this area.

Resume

La peche a la crevette nordique (Pandalus borealis) de la r6gionScotia-Fundy couvre trois zones situees a des profondeurs de plus de100 brasses, design6es sous le nom de trous de Canso, de Louisbourg etde Misaine. Au cours des derniares annees, ces zones ont toujours etesous-exploit6es: en 1987, seulement 152 t (7,1 %) du contingent toalde 2140 t ont 6te captures. Ces prises correspondent a un tauxd'exploitation de 2,0 % d'apres l'estimation de la biomasse totale(Etter et Mohn, 1987).

L'effort a de nouveau 6te faible cette annee, sept bateaux ayantdeclare des captures. De ce nombre, trois provenaient duNouveau-Brunswick (plus de 65 pieds) et ont preleve pres de 91 % dutotal des prises. Du total des prises, 148 t provenaient de la regionde Louisbourg, ce qui representait 13,8 % du contingent de Louisbourgfix6 a 1 070 t. Les quatres autres tonnes ont 6te prelevees dans letrou de Misaine, aucune prise ne provenant du trou de Canso. Lesquatre autres bateaux qui ont participe a la peche etaient des naviresdont le port d'attache etait au Cap Breton (moans de 65 pieds). Lespecheurs utilisaient surtout les chaluts a crevette Sputnik et Yankee41 de maillage reglementaire (40 mm). Cette peche est gravementtouchee par une limite de prises accessoire fix6e a 10 % difficile aatteindre dans cette zone.

3

Input Data

Commercial Data Commercial data for this report came from the logbooks and the

Foreign and Domestic Quota Monitoring Unit, Fisheries Operations Branch. The logs were at about 83% coverage with the official statistics for these areas.

The average yearly commercial catch rate (corrected values to Yankee 36 trawl) for Louisbourg was 39.9 kg/h (Table 1) which is the lowest value seen in the past six years (Table 2). The correction factors used are shown in Table 3. This low catch rate may be a result of the very nigh coverage rate of log information this year. The information that was available this year that has not been in the past was from boats that landed their catch in Northern New Brunswick. The low catch rate may therefore be a factor of spoiled catch. The total landings this year of 152 t is an increase from the past two years and is consistent with the increase in effort. Table 3 shows commercial catch rates according to gear type. There se~ to be trend toward using larger nets in this fishery, as in the past year the Sputnik has been used more often than in the past. This may also account for the decrease in the average catch rate of commercial vessels as it is corrected for the smaller Yankee 36. After correction factors have been applied there appears to be a substantial difference between gear types, indicating perhaps overcorrection and a need for research on trawl efficiency.

Figure 1 shows monthly catch rates from the commercial fishery and research cruises for the period 1977 to 1987. The commercial catch rates show a falling trend through the years, although 1982 and 1985 are slightly different in that they don't really reflect a general decrease in catch rates during the season. It also shows a very high catch rate in the fall research cruise of 1987 that does not correspond to the commercial catch rate at the time.

Research Data As has been the practice for the past six years, two research

cruises were completed in 1987 (May and October). Standard tows were

carried out, as in previous years, for half hour durations at a nominal speed of 2.5 knots using a Yankee 36 trawl with a 40 rom mesh size. The results of these surveys are displayed in Table 4 and graphically in Figures 2 and 3. The shrimp catches from research cruises are corrected taking tow length into account. The holes are defined by the 100 fm depth contour, where stations were allocated randomly inside the single stratum for Canso and Louisbourg holes. The Misaine stations were random stations which are carried over from year to year to save searching time for fishable bottom.

4

The average catch (kg/tow) as seen in Table 5 shows an increase in Canso and Misaine catch rates in 1987, with a slight decrease in Louisbourg. There appears to be an increasing trend from 1985 values. The shrimp fraction by weight, approximately 23% of the total catch in 1987 (Tables 6 and 7), is higher than any value seen previously, except for the 1983 research data. As before, the commercial logs show a higher catch percentage of shrimp than the research cruises, presumably because the fishing captains are directing for clean catches. The redfish by­catch from the commercial logs which in the past has been frequently above the 10% limit seems to have decreased this year while remaining high in the research cruises. The by-catch levels from the research data are closer to the values seen in cruises previous to last year's where there were high numbers of cod and silver hake. Figure 4 shows the cod and redfish by-catch size distributions from the research cr~ises in 1987. From these it appears that Louisbourg has the highest by-catch levels of cod while Misaine has the highest for redfish. The peak of redfish (20 ~~) in Louisbourg in the fall (which was from one unusually large tow containing mostly redfish) consisted of smaller animals than those seen in the Misaine area (35 em).

Samples of shrimp approxL~ating 500 animals, were collected for each tow completed. These animals were individually measured and sexed to determine length frequency distributions. The distribution figures are based on measurement of carapace length, to 0.1 rnm, and then grouped into 0.5 rnm groupings. Figure 5 separates the data by area showing sL~ilar distributions for the three holes. Grouping the data by sex we get Figures 6a and 6b, with the number at the top of each figure being the number of individuals in the total sample. In comparing the graphs from the 1982-1987 spring/fall research cruises we can see the large portion of transitionals that are present in the spring disappear from the population in the fall. We also detect two peaks of males supposedly representing two year classes which can be followed from spring to fall where they peak at a slightly higher length. This is also shown in Table 8 where the peaks have been labeled as group I-IV+. Here in the fall, groups III and IV+ become a single group of females.

According to McCrary (1971) the presence of sternal spines in female pandalids determines them as not having previously spawned. Dividing the females from the 1987 research cruises into those that have previously spawned and those that have not, as determined by the condition of the sternal spines, we see from Figure 7 that the females with sternal spines are present in larger numbers in the spring, and appear to have the same size distribution as spawned females. Table 9 covers the percentage of females with sternal spines from 1982-87 and generally shows a higher number of females with sternal spines in the spring compared to the fall. The spring of 1987 revealed an exceptionally high percentage (14.9%) of these females. Using this information to do a regression analysis, we see from Figure 8 there is

5

an inverse relationship between the number of females with sternal spines and those without. It also appears that from Figure 9 there is a slightly negative correlation between transitionals and spawned females and a positive one between transitionals and females with sternal spines.

There were two stations done in the fall 1987 cruise in the Canso area that were repeated one week later. The length frequencies for these samples (Figure 10) show very similar distributions between the initial station and its repetition. Also, two exploratory tows done in both the spring and fall cruises of 1987 shown in Figure 2 and 3 (outside the three areas and closer to shore) showed relatively high catches of shrimp. This indicates that the biomass estimates based on the three fishing areas outlined are not encompassing the complete abundance of animals and therefore would represent an underestimate. The length frequencies of the samples in these exploratory areas are shown in Figure 11 and indicate a very high incidence of males in the spring samples with virtually no females present. In the fall the males are not as abundant and there is a large group of females present indicating some movement of animals from one area to another. We also see a slightly smaller size of animal in the modes determined for these exploratory samples compared to the samples from the original areas.

Figures 12a and 13a show normalized research catch rates for Louisbourg and Canso holes. The catches from each station are normalized by dividing by the average catch for that particular cruise and plotted according to area to make comparison possible. We can from these maps pick out some patches of high concentrations of shrimp. These concentrations do not appear to be correlated with depth (Figures 12b and 13b) and do not seem to follow close to the 100 fm contour as reported by some fishermen.

When we consider biomass estimates we see a low value in April 1985 (Figure 14) with a slight increase since that time. As an index of stock health, the number of ovigerous females was compared to those non­ovigerous (Table 10). In the fall virtually all females are ovigerous as in our fall sampling from 1982-1987, approximately 153 out of 34,600 females were not.

Bottom temperatures collected for approximately 50% of the research tows revealed a slightly increasing trend from 1982-1987 (Figure 16b). When grouped by area in Figure 16a, it appears that the high temperatures seen in Canso last spring, are back to previous levels, and correspond to increased catch rates in 1987 for this area.

Assessment Results

For each hole the biomass was estimated by areal expansion, where the horizontal opening of the research gear was assumed to be 36 ft. The standard tow was 1/2 h at 2.5 knots giving a length of 1.25 nautical miles and a swept area of approximately 1/135 of a square nautical mile. The areas of the three holes measured by polar planimeter (using the 100 fm contour) were 276.4, 472.2, and 442.2 square nautical miles for Canso, Louisbourg, and Misaine respectively. Tow lengths as seen in Figure 15, ranged from 1.1 to 2.2 km and show no relationship between longer tows and higher catches. The tows were however corrected for length as defined by the start and end positions. The catch rates

-----------------------------------------------------

6

(kg/tow) for all research cruises have been calculated taking tow distance into account, resulting in generally lower average catch rates than previously stated. The average catch rates from the research cruises were standardized to Western 2A catch rates by multiplying by 1.5 to account for the vertical distribution above the Yankee 36 (Labonte, 1980).

Biomass, standard error, and proposed catch levels (t) from survey data, 1987.

Cruise Recommended Area catch

May October Avg. levels*

Canso 1248 ±482 2082 ±498 1665 580 Louisbourg 1972 ±365 3752 ±516 2862 1000 Misaine 2429 ±331 4007 ±384 3218 1130 Total 7745 2710

* Rounded to the nearest tens.

The recommended catch levels were derived from the biomass estimates (see above table) using an exploitation rate of 35% as was used in previous analysis and recommended by CAFSAC.

Quotas (t).

Year Canso Louisbourg Misaine Total

1980 1086 1553 2382 5021 1981 1982 1000 1400 1800 4200 1983 1400 2000 2400 5800 1984 1400 1800 2500 5700 1985 1350 1790 2420 5560 1986 740 1460 1600 3800 1987 210 1070 860 2140 *1988 580 1000 1130 2710 **1988 370 1160 1050 2580

* Proposed values. ** Values based on the average of biomass estimates from 1986-87.

The recommended catch level of 2710 t (determined from the 1987 biomass estimate) is up from last years value. However when you use the average biomass estimate for the last two years (Table 11) you get a lower level of 2580 t. Last year's quotas were determined on the average biomass of 1985 and 1986.

Discussion

The biomass estimates in 1987 show an increase from 1985-86 values which were a considerable decrease from previous years (Figure 14). The fact that these years show a greatly decreased biomass from previous years suggests that in using a long-term average to determine recommended catch levels, one is ignoring a strong indication of a

7

change in biomass. Even so, exploitation rates have never reached their quota levels. The abundance of shrimp in Canso and Misaine seem to be on the rise in 1987 while Louisbourg does not. The extremely low numbers of shrimp seen in Canso in the spring of 1986 which mayor may not have been related to the high temperatures and/or an increase in silver hake evident at that time, are not as low in 1987. The temperatures and levels of by-catch have returned to a value closer to the overall average for this area. This suggests a fluctuating biomass driven more so by biotic and/or environmental factors, than by fishing. The past three years saw virtually no commercial exploitation in this area.

It appears that the presence of mature or spawned females may inhibit the formation of females from the transitional stage. (Figure 8). When females withput sternal spines are present in large numbers, females with sternal spines are not. In determining confidence levels in a regression analysis of the two groups of females (for each individual area and the three areas combined) it appears they are all significant at a 5% confidence level except Misaine. Since the females with sternal spines are present in larger numbers in the spring they may be the result of males that have put on a large spurt of growth during the winter months. The spurt is evidenced from the difference in the distances between peaks in the spring compared to the fall. There is a larger distance between the mature male peaks from the fall to the spring compared to the spring to the fall (Table 8). This all goes to support the idea that spawned or mature females may inhibit females with sternal spines and transitionals. This is complementary to the supposition that animals may pass directly to the female stage in times of depressed biomass. Presumably, this is a result of the same mechanism that inhibits the formation of transitionals and females with sternal spines when the mature female biomass is high.

The recommended catch level based on the 1987 biomass estimate is 2710 t. Using the average biomass estimate for 1986-1987 you get a lower value of 2580 t. The recommended catch level used to determine a quota last year was based on an average of the two previous years.

Unless changes occur this potentially valuable resource will likely continue to be underexploited in the near future. Although prices are favourable, the catch rates at this time are not high enough to entice participation. The by-catch limit also poses a problem since it seems to be very difficult to adhere to this limit when directing for shrimp. This would seem to necessitate a provision in legislation.

References

Etter, M.L. and R.K. Mohn 1987. Scotia-Fundy Shrimp Stock Status ­1986. Can. Atl. Fish. Adv. Comm. Res. Doc. 87/10.

Labonte, S.S.M. 1980. An assessment of shrimp stocks off southeast Cape Breton, South Esquiman and North Anticosti. Can. Atl. Fish. Adv. Comm. Res. Doc. 80/67.

McCrary, J.A. 1971. Sternal spines as a characteristic for differentiating between females of some Pandalidae. J. Fish. Res. Bd. Canada 28: 98-100.

---------------------------------------------------------

---------------------------------------------------------

8

Table 1. Monthly commercial shrimp fishing infor.mation for Louisbourg and Misaine areas (1987).

May June July Aug Sept Oct Yearly

Louisbourg: Catch (kg) Effort (un) Effort (cor) CPUE

9979 111 333.0

30.0

27818 305 422.0

65.9

47440 512

1119.5 42.4

10433 105 315.0

33.1

20865 195 585.0

35.7

4211 75

225.0 18.7

120746 1303 2999.5

40.3

Misaine: Catch (kg) Effort (un) Effort (cor) CPUE

3761 59 76.7 49.0

1685 30 90.0 18.7

5446 89

166.7 32.7

Both areas: Catch (kg) Effort (un) Effort (cor) CPUE

126192 1392 3166.2

39.9

Table 2. Scotian Shelf commercial shrimp landings and CPUE.

Catch(t) CPUE(kg/h) Year

Canso Louisbourg Misaine Total Unstd. Std.*

1977 269 128.5 104.5 1978 306 121. 9 97.3 1979 534 295 8 838 174.6 128.0 1980 360 491 133 984 130.9 97.3 1981 10 418 26 454 131. 8 92.8 1982 201 316 52 569 128.0 80.4 1983 512 483 15 1010 127.7 81.2 1984 318 600 10 928 109.5 77.6 1985 15 118 133 75.4 40.7 1986 126 126 87.3 58.1 1987 148 4 152 90.7 39.9

* Standardized to a Yankee 36 trawl.

Table 3. Catch rates (kg/h) for commercial boats off southwestern Cape Breton, 1987.

No. of Gear Louisbourg Misaine Cor. boats type Area Area factor

1 Sputnik 33.22 18.72 3.0 2 Yankee 41 63.56 49.04 1.3

------------------------------------------------------------------------

------------------------------------------------------------------------

------------------------------------------------------------------------

------------------------------------------------------------------------

9

Table 4. Tow information from scientific research cruises.

* Cruise Area Tow Depth Bottom Shrimp Cor. Total

(fm) temp (kg) (kg) (kg)

May 1987 Canso

Louisbourg

Misaine

1 133 2.3 1 1 430 2 106 1.8 15 10 64 3 105 1.9 15 11 74 4 102 12 8 60 5 105 2.6 11 7 47 6 111 3 2 14

28 157 36 27 59 29 111 1.7 57 41 106 30 132 1.6 122 91 143 31 127 1.4 33 25 61

7 129 3.9 32 21 73 8 128 3.8 49 32 127 9 147 3.8 32 24 79

10 131 33 25 136 11 132 3.8 46 33 98 12 134 11 8 31 13 149 3.9 12 13 34 14 167 3.9 14 11 43 15 180 1 1 84 16 136 34 38 100

17 131 72 56 183 18 139 0.6 29 25 71 19 129 0.8 45 34 88 20 164 0.8 40 36 77 21 130 25 33 107 22 132 1.5 38 25 106 23 107 1.4 24 19 76 24 118 1.5 21 15 47 25 111 1.7 24 16 54 26 124 23 16 44 27 127 1.8 30 22 816

Total 940 726 3532

... Contd.

------------------------------------------------------------------------

------------------------------------------------------------------------

------------------------------------------------------------------------

------------------------------------------------------------------------

10

Table 4. Contd...

* Cruise Area Tow Depth Bottom Shrimp Cor. Total

(fm) temp (kg) (kg) (kg)

Oct 1987 Canso

Louisbourg

Misaine

1 104 3.3 13 8 117 2 106 3.3 35 29 208 3 104 3.2 19 18 125 4 109 2.1 8 8 251 5 118 3.1 34 31 202 6 110 11 10 129 7 162 3.0 89 83 151 8 135 2.2 70 59 88 9 107 2.1 62 51 123

10 134 2.2 80 75 104

22 156 3.0 77 66 580 23 142 14 14 47 24 151 4.1 20 19 248 25 151 4.1 53 58 96 26 145 4.1 31 26 94 27 130 3.8 54 49 241 28 124 3.8 47 43 117 29 129 3.5 37 34 93 30 112 3.6 38 51 137 31 151 3.7 37 32 104

11 120 2.7 57 50 347 12 114 38 37 255 13 113 2.3 48 40 103 14 116 2.3 33 28 1655 15 131 2.3 50 42 177 16 138 2.0 32 27 229 17 119 1.2 54 57 234 18 145 38 35 151 19 133 1.5 60 56 132 20 135 1.6 80 75 177 21 122 1.6 54 43 158

Total 1373 1254 6873

---------------------------------------------------------------

---------------------------------------------------------------

---------------------------------------------------------------

------------------------------------------------------------------------

------------------------------------------------------------------------

11

Table 5. Average catch (kg/tow) from research cruises.

Area Year ---------------------------------------

Canso LOuisbourg Misaine

1982 56.8 41. 4 34.2 1983 114.5 62.3 117.4 1984 45.6 44.5 57.0 1985 13.6 24.3 24.1 1986 8.2 39.3 30.7 1987 29.8 29.9 35.8

Table 6. Percentage catch composition of shrimp tows.

May June July Sept Oct Species

Res** Com* Com* Com* Res**

Shrimp 26.5 56.7 69.8 49.1 20.4 Cod 18.2 32.8 20.7 3.3 12.3 Redfish 26.0 5.4 2.9 43.8 36.9 Flatfish 8.8 3.1 2.0 1.8 10.6 Hake 14.0 0.1 0.4 13.4 Halibut 0.6 0.1 Haddock 0.1 0.2 Pollock 0.9 4.2 0.7 Misc 6.5 0.3 0.4 0.8 6.5

Total shrimp 726 14889 34766 11793 1254 catch (kg)

* Commercial log data. ** Research cruises.

Table 7. Corrected catch rates in kg/h (left-hand column) and percentages (right-hand column) of individual species in research cruises (1982-87) .

Cruise Shrimp Cod Redfish Flatfish Hake Misc. Total

Apr 82 58 20 76 26 72 25 34 12 51 18 291 Nov 82 120 21 117 21 50 9 86 15 147 26 48 8 568 May 83 212 37 100 17 160 28 47 8 58 10 578 Nov 83 169 33 83 16 16 3 58 11 122 24 62 12 510 May 84 132 24 140 25 222 40 30 5 31 6 561 Oct 84* 64 13 88 18 86 18 43 9 169 35 35 7 486 Apr 85 32 19 35 21 49 30 24 14 27 16 167 Oct 85 50 19 34 13 63 24 18 7 80 31 17 6 261 May 86 71 13 170 32 90 17 37 7 117 22 50 9 537 Oct 86 34 11 31 10 107 35 28 9 86 28 21 7 307 May 87 47 26 32 18 46 26 16 9 25 14 12 7 177 Oct 87 81 20 49 12 147 37 42 11 53 13 26 7 398

*Change of trawl door.

------------------------------------------------------------------------

------------------------------------------------------------------------

------------------------------------------------------------------------

------------------------------------------------------------------------

12

Table 8. Length (mm) of shrimp at peaks of length frequencies by sex.

Year I II III IV+

Spring 1982 14.5 19.0 22.5 25.0 1983 18.0 23.0 25.0 1984 14.0 20.0 23.0 24.0 1985 19.5 23.5 24.5 1986 15.5 20.5 23.5 24.5 1987 15.5 20.0 23.5 24.5

Fall 1982 17.0 20.0 25.0 1983 17.0 20.0 24.0 1984 16.0 21.0 25.0 1985 17.0 19.5 25.0 1986 17.0 20.5 25.0 1987 16.5 20.5 24.5

Table 9a. Females with sternal spines as a percentage of total females (Spring) .

Year Canso Louisbourg Misaine Total* % * % * % # %

Apr 82 6/826 (0.7) 4/1532 (0.3) 1/920 (0.1 ) 11/3278 (0.3) May 83 8/1030 (0.8) 5/1234 (0.4) 11/1139 (1. 0) 24/3403 (0.7) May 84 33/611 (5.4) 41/1130 (3.6) 37/840 (4.4) 111/2581 (4.3) Jul 84 5/165 (3.0) Apr 85 19/861 (2.2) 1/1243 (0.1 ) 4/1348 (0.3) 24/3452 (0.7) May 86 10/133 (7.5) 82/866 (9.5) 8/1152 (0.7) 100/2151 (4.7) May 87 76/382 (19.9) 78/876 (8 . 9) 131/655 (20.0) 285/1913 (14.9)

Table 9b. Females with sternal spines as a percentage of total females (Fall) .

Year Canso Louisbourg Misaine Total # % # % % # %*

Nov 82 4/2190 (0.2) 1/2223 (0.0) 9/2640 (0.3) 14/7053 (0.2) Nov 83 2/1597 (0.1) 1/1323 (0.1) 3/2920 (0.1 ) Oct 84 0/1488 (0 .0) 0/2022 (0.0) 2/2221 (0.1) 2/5731 (0 .0) Oct 85 2/1719 (0.1) 1/2340 (0.0) 6/2511 (0.2) 9/6570 (0 .1) Oct 86 6/1342 (0.4) 4/2764 (0.1 ) 16/2329 (0.7) 26/6435 (0.4) Oct 87 2/1701 (0.1) 0/2064 (0.0) 3/2098 (0.1 ) 5/5863 (0.1)

----------------------------------------------

13

Table 10. Numbers of ovigerous/non-ovigerous individuals in samples from research cruises.

Non-ovigerous Ovigerous females females

Spring Apr 82 2638 650 May 83 1330 2085 May 84 2574 12 Apr 85 3211 246 May 86 1286 866 May 87 351 1567

Fall Nov 82 52 7016 Nov 83 11 2917 Oct 84 15 5716 Oct 85 21 6551 Oct 86 40 6396 Oct 87 14 5852

Table 11. Research vessel biomass estimates (tl

Area

Year --------------------------------------Canso Louisbourg Misaine

1978 3900 5600 1979 2900 4300 9600 1980 1981 3000 4100 5000 1982 3180 3970 3080 1983 6410 5970 10560 1984 2550 4250 5120 1985 760 2330 2170 1986 460 3760 2760 1987 1670 2860 3220

Average 2760 4130 5190

--

200

1977 1978 1979 1980 1981 1982

150 -I

~ 100 -I ~ V\

0

/\ O~~ ~ ::c Ol 50 ~ £ U ca u 0 a. 1983 1984 I 1985 I 1986 I 1987E

.1:: 0 £

~ ~

Cf} 150 J 0

100 -I \/\ -i 0 ~

50 -I "'-- ~)\ 0 ~

I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I FM AMJ J A SON D FM AMJ J A SON D FM AMJ J A SON D FM AMJ J A SON D FM AMJ J A SON D

Figure 1. Shrimp catch rates by month from 1977-1987. commercial boats (standardized)

o research cruises

46°00'

I''' .......'''' ..,:...

"---_.,'/ \----"\ --- 42 I ,'_I

/--1$4 • .22 :' 'It Z'Cape Breton .:;./ ,-, • .'--, 26 ," ,,/" ! (--' )'. '-- I 50"". //,' :, ,--.J'l­

f \.' ..."','" '" I , __ ... :::cJ ,.-, ,) - • 16 (/,/ /':....____ \ ',,~,:(~,::::::-::.~ ... ' .......... ' 48- -,"' ... '" " _"" ...,/ \,I"~ '-,' - 66,,/" />:._<::::),-;' ,/

.. "".... ,"----, r' , .. ",--' j" ,1 , .. ~"", ,1""," ,'.. ' ... ,/ >,,-_! ';:-'7ir L/ ..-,:::/',J < .:-- {,' (; .,_/'\~ ,~-:/--"''''''

''''II .;:::':'," ''', '''ti,'.\/( \\ Ii)) ... 'f'J '-. Louisbourg,,,//32L ....." \... ".,'" :J204

I-' Ln

,-....

:"f~/ Canso / Misaine ,~. 45°00' ../' -..- . _ F\ I ,_,-;;:,­

,-' -161. ---;;'" ,-. ,/if' / '" \} I r" ...... ___" " ,~ , : ': :-'_, __';:.", t' 112 ", • \ :~ 4

: ,> \.... \ t; ~I : 82 'II) I: 3') ) \. '. " ! 1\ l ~ ,,: \'\. \ \ ,..,! ~ \~,. ,,:, / /'" h " J ,I • 20: I I , .. , 'II,., ,.. ...... I, .. ... ",' I " • ~ I J If,\ \ __, ..... , .. '72 ".... I I'"

r \ 22 I I I '\ \.. / ,..... I , ........:.;.:.... ...."'" to", 50 I I}: :: , __ J \ \ .. ~~, .. / \' \'''' \ !,,.t••J ' .. l ...1 I 182"t t ....... 1 I "-, I ,',,\ ; ...., I' ....' \ " '" II I' t .... I"~, ,"....... _.., "".. ( " ""__ '\ "_'#

I # .. ... I I ,. '\ "....." ' ;: \ , " ... ' '''.,... I ," __,.' " • - I ,... ' \ I 5Q' , ,{,'\.......... '~ \t 2 L ..' ..... , ''''''-.. /,,,, '...... -\.. .jt_;I ('",~''''' ,./54: J /, '",\ 32: : ( '';' '''''''-''''' : ,t ~ : A \ ;-\ t t:··~ ,: ~.. ,,' ,...\ ,,'" f'\ \......'......_,... 1,\1 '........ '' ,.. , - 50'- ...... I I ,I \.. \ • I'" I • , ..... , I ..... \ ,_ I... _.... .. \ 68 ' " f "-"l ', ..... -... ,.';,:1 \... -,......~: I .. , ,'. ') \: .....30......,,' \ \ t .:'.. ~,..\ \J \ r: t_... '\ \ f\ r:- ..... l ' ,.... .. I , ..., \ \ I I 1 \ , \ ...... ,,'" , , 66 \ .. • .... ........ .. I

\---:. ).\';) (' i '/r-' \ \, ,-.44" I-:;~ "::::-. \J\ ,,~:\ '>f \. _,-~'.. 1'----' v -" '.' c." \, " .. , I '. - .. \ • I'. I I,,;' J , ' \\" I ..... .i'" t_ .... '' " • VI,' ,/ '-. \ \. / \t ,;/ (38 \;', 1i \:-\ ../ i .(,__ /--,l \ \, .: \', -',_) \\ : \ -' ,-'" \ \ ,','" .......':~ - ,-, '......

'.....l ('\ \ \1 , I , I L'

61°00' 60°00' 59°00' 58°00'

Figure 2. Shrimp catch rates (kg/h) from the May 1987 research cruise.

46°00' ","';

,,;''''' ....iI t" , ,/ ' ........ -""..,

"""'----_.... ,.,. \/' .38: ,,( Cape Breton ,/'-: 68 .52 .116 j :'28'"

...:------~ /;' /",.., l ~..... - J: , , ....:/ ,/" l \ ............. -.....q'O

-,-~ ,,' • 102 86 I " ,: " ,______ ',"':",~~-~-----...:::::~> ,.' .. -....' • ",-'"," ,i/........ " \',1 '" c.,64 ..'''''''' .......... , ....';:.. '" / .. ;::~ .....' ..>'-:-46 ""' ...., • , ..... -......) • /'" .......-"...:..' ... I-::~"::"":"'/'· ........' ...

l ",l ',,9ji;: ,....;......._ l I' .. •_.......",'" / ...11 132 " ,.. " ,'" I / • ..,. ... l \', ,,/' ..............•,.... ~./ t/" ,-, \ "' .......--- ............

" '-' '", ~::.::~~ .. ...,:, f':','\\ I'" 182I~ \1 ;.... J\ .../,,,,1 Louisbourg,..... ' •'----1·38r '. ;, :/

.j

t-' 0\

"/';~i~ Canso / Misaine ••p

45°00' ,-' / ,-, I _'-:;-'/~,' 36:, ----,...- _ r/~ 1'-', (,) I r-' " • ('7 :_,_ _--;'":.',,! ( ... ." , 162 ( ; I ' " I. ,----,.' I. " , ". I .' ", Ii '.'

,,' 58 I :,.: ) '" '{, J ,,} I I l ~\ .', : \ 0 Ii \" \\_S'.1 ,~, ) / ,:~,// i\ 1/86 I'.... • f I l ...... '" .... , ,.. ,.......... 2 I } 80..-...... -.. ... ........ 1' ,,' \. l I, I ,-'" j \ ...~~ ... " /70 \ '" c;:n" \ :_~, : ..: I 118~. f;;":;'~' l .. -.. 10

I I"";'" • ........ '....... ,... -.... '''5l}' ..,' \.': : \ • ", 7" I'""',",,,,,,_;,.~ /\ l """"'Y\', ..._,/ • "'" - • " --,., " ,., 1,' , ',. I I '----', _ • I " """'.'"l • 19....... 'J I .... \ ...-,.\ ).. , I ,. *, '1 I 4', '''' __ ,.. .. I \ I"" f \', ... .. I " .. " ' '_.. ,_" .... ", I .......• - , ", '-, ,,)..., ,',- , • I - • I. ". " ",. " I, • I) ',.' I , "

t" ~ ...-- l 20'" ..."".,' ...... ..-""" t ' .. J I " ... ,,, \ • I.... f 54'.' I ..../\ '" .. ',\ \........ I.. _" '\ • _ ..~, .:' '--, '~'" • ,,;,;. \.':'1 {, I ~/J 74 '; \: ,- '\ :' \ \ t., :~~' \, "J ,\ rl ,_, \ .. [\,tJ,2--:-,..• 'I '''-''''t:;.-,' "', \, • , '. ,-,' , " '" .. 114 f, • \ I ... "" "'. " 1·_. 1>0'1' : " ,,- \" ,'~-~, ',_ '._ \ r- '.', ~:, ,_' ~ r----' . -.. ' ,';"\,' (", :" ". \: G f ~~! ,;') - \\,,, : '., '::, L ,,/

, ., I " \.,' ., / • ~ ',:: ", ,~,' \ \ .: '~," <',_. 84 \ I, '" ,. "150,·, \ "100 ,\ ,_, to' .,'. \ \ 1/' ' ......-~ _"*"'/ , .....\ \ \.1

61°00' 60°00' 59°00' 58°00'

Figure 3. Shrimp catch rates (kg/h) from the October 1987 research cruise.

20, 400 REDFISH ..........._h....." ............._ ........uCOD Canso Canso

----- Louisboufg ---- .. Louisboufg~ Misaine/, Misaine

151 300 I ' I : I ,.. I ,IISPRING

10 ~ 200

,I '\ 5-1 ,I J}' 100

I I I ..,~~

o I 0 >- 0 20 40 60 80 100 120 0 10 20 30 40 500 c Q) ::::I t-o CT '-I Q)....

LL 20, 400

, ,, , J \ I \

I ,,

I ,I

\I

,...,151 3001

FALL 10 ~ 200

1 5-1 100

.......- ..... o I 0

0 20 40 60 80 100 120 0 10 20 30 40 50

Length (em)

Figure 4. Length frequencies (by area) of cod and redfish by-catches in 1987 research cruises.

400

18

600 May n = 12071

_ ..- Canso 500 - - -- - Louisbourg

Misaine

>. u c (I) 300 ::::l t:r' ~

U.

200

100

0 5 10 15 20 25 30 35

Length (mm)

600 October n =12696 --_...... Canso

500 ----- Louisbourg Misaine

400

>. u C (I) 300::::l t:r' (I)... u.

200 ~ I \ I \

O~--~~--~~T-~--~--~~~~~~--~~

5 10 15 20 25 30 35

Length (mm)

Figure 5. Shrimp length frequencies by area, 1987.

100

1000SPRING

800

600

400

200

0 5

1000,

800 >. 0 c (U 600::J c­(U... 400

200

0

I..L.

5

1000

800

600

400

200

0 5

10 15

M

10 15

20

J ,

20

1982 1000 I FALL11957 14106 800

600

400

200

0 25 30 35 5 10 15 20 25 30 35

1983 1000 14225 I 5832

800

T 600

U ~ 1.0400 I ~

200

0 25 30 35 5 10 15 20 25 30 35

1984 1000

800

600

400

200

0 25 30 35 5 10 15 20 25 30 35

Length (mm)

Figure Ga. Shrimp length frequencies by sex (1982-1984).

10 15 20

1000 I1000 ~ 11366 1985 A 14.t1~ FALLSPRING 800

600

400

200

0

1000

800

>­0 c 600 (I) ::l rr (I) 400 ~

LL

800 T

600

400

200

0 5 10 15 20 25 30 35 5 10 15 20 25 30 35

1986 1000 8468

800

600 I NMJ\ J \ I \ F a T 400

2:1 d.AK. 200

0 5 10 15 20 25 30 35 5 10 15 20 25 30 35

1987 1000, 1000

800

600

400

200

0

12071 12696I 800

600

400

200 F

0 5 10 15 20 25 30 35 5 10 15 20 25 30 35

Length (mm)

Figure 6b. Shrimp length frequencies by sex (1985-1987).

21

1000 May

800

600

400

200

,Il 1\ IVI I I , I

.. .11;-..1 I

r\/ V \ ! ; \ I .f'. j Ii'\ \

.... i:! I i I'

)\: \ .:f \.\ .fiiii Y

/ I ! I

._--....__.. Males - - -- - Transitionals

Females w/o sternal spines •.•.•••.•. Females with stemal spines

O~~~~--~~~--~~~-F~~~--~:'r-~~

5 10 15 20 25 30 35

Length (mm)

1000 October

......-.~........ Males Females w/o sternal spines

800 ........... Females with sternal spines

600

400

200

10 15 20 25 30 35

Length (mm)

Figure 7. Shrimp length frequencies by sex (differentiating females by sternal spines). 1987.

•

ot-~~~~~~~~--o 500 1000 1500 2000

Females without Sternal Spines

300

(f) Q) c

~ y = 2974.7" 1 0"(-6.4962e-4x) RI\2 == 0.875

(f) Q)

~ Q) u.

O+---~----~--~----~~~--~

150

(f) Q) c

~ "ffi 100 c.... Q)

U5 -:S'?a (f) 50 Q)

"ffi E Q) u.

0 0

150

(f) Q) c '0. (j)

"ffi 100 c... Q)

U5 .r::. .~ (f) 50 Q)

E Q) u.

•

22

y = 310.66" 10"(·1.4322e-3x) R"2 = 0.473

, •

500 1000 1500 2000

Females without Sternal Spines

0 Canso

y == 203.92 .. 10"( -1.4540e-3x) R"2 == 0.801 Louisbourg•

y = 4210.9" 10"(-2.252ge-3x) RI\2 == 0.657

c Misaine

y == 454.58 * 10"(-1.6571e-3x) RI\2 = 0.426

1000 2000 3000 4000

Females without Sternal Spines

Figure 8. Regression analysis comparing females with sternal spines to those without.

• •

• •

• •

1600

23

• .. y= 1499.3· 10"(-1.7536e-4x) R"2 = 0.179

1200 •

(/)

cti •c: .2 800 •·11 c: ~ • l ­ • •

400

o+---~--~--~----~--~--~--~--~

o 500 1000 1500 2000

Females without Sternal Spines

150

y = - 16.248 + 4.5354e-2x R"2:::: 0.129 •

100cti c:... d,) •US .~-= (/) d,)

cti E d,)

u..

Figure 9. Regression analysis comparing transitionals to females with and without sternal spines.

50

o 400 800 1200 1600

Transitionals

5050 ................. Males C09 Females

C06 n=440n=444

4040

1Ii,:3030

~.

1 \ 1\: i I: : ,..2020 Ii i

• : i····/ ::: : r \ i I I

i I Ii: i i f \ i \1' \i ! lit if ii !! i : r1010 I l.:

: "i f i i !

:

I I : I : \ !i t . :

o I :...;...... / i i '.--" "> i o 5I I V l i --oj 'J )

5 " ~ o>­ 10 15 20 25 30 35 10 15 20 25 30 35 c Q) :J CT Q) N L. -I>U.

50 RepeatC06

50 RepeatC09 n=549n=455 l4040 't

It JIi ii

30 30~ f \ Hr• ~ II, !i '" Ii Ii!i f i I I

I i'! i j i 20 20~n , \ , \ f \/ \

! I i l !!~ i I Ii! i: \1 i \ i \10 10 . \ i .I ~...J " i

,

Us 1 o I 1\.1. ,;i I i'~ o I '? i "', • ;==-. ,•

5 10 15 20 25 30 35 5 10 15 20 25 30 35

Length (mm)

Figure 10. Stations and repetitions from the Canso area in the October 1987 research cruise.

.. ., ..

150

100

50

25

, May ~ ! \

I I

MalesI \ i I Transitionals t ! Femalesi I I ! i i i ji i

i i i

i I \ l

Ii"! \ , ,

i \ I,

! \ :' A :'1. i \ I h / \ ! v..•' \r ~ i (''/ \

j \./ f\ \ ) \.... /\ I

..l o+-~--~~~~----~~~--~~--~~~~

5 10 15 20 25 30 35

Length (mm)

150 October

Males Females

100

J50

:f'\1\ i A

\ i \ ./ \ ! \" . i Ir '\

/ \, .' \ "I.,.., "

O~__~__~~~··~i~__~__~~\~.~~~~__~__~~ 5 1 0 15 20 25 30 35

Length (mm)

Figure 11, Shrimp length frequencies by sex from the exploratory tows, 1987,

26

45 00'

44 45'

Canso

o o4 o

o

61 00' 60 30'

Figure 12a. Normalized catches for Canso area (1982-1987).

5

Figure 12b. Normalized catches verses depth (Canso).

f"! t I •

46 00'

27

45 30'~----------r---------------------------~--------------------~ 59 00' 58 30'

Figure 13a. Normalized catches for Louisbourg area (1982-1987).

5

4

J: (..)

(tj 30

(1) >«::c 2(..)

~ 0

1

0

Louisbourg

0

0 0 0

o 0 00 CO1:00 ~ ~ 0 ~ ~ §~ ~ o 0 fPO,~~o 0 o 0 o 00 00

80 100 120 140 160 180 200 220

Depth (fm)

Figure 13b. Normalized catches verses depth (Louisbourg).

••

28 . ..

30000

o Total Biomass • Fishable Biomass

20000-~-(Jl (Jl Ctl E 0 ljj

10000

APR NOV MAY NOV MAY OCT APR OCT MAY OCT MAY OCT

1982 1983 1'984 1985 1986 1987

Research Cruise

Figure 14. Biomass estimates from research cruises.

125

100

-~ 75-..c £ Ctl U

'$ ~ 50

U5 0

25

0

0 1.2

0

0 May

• October

• • • 0• • ••• , • • 0

0 0• 0

•• 0" 00. ",. o Co 0 0

0 000

•tit

• •l} 0

• 0 0

0

1.4 1.6 1.8 2.0 2.2

Tow Distance (km)

Figure 15. Shrimp catch per tow verses tow distance from 1987 research cruises.

29

7

6

(.) 5-0-Q) ~

:::! 4 "@ Q) a. 3E Q) I ­

2

1

0

7

6

5u­0-~ :::! 4 "@ Q) a. 3E Q) I ­

2

1

0

• Canso LouisbourgII

m Misaine

Apr82 Nov82 Nov83 May84 Oct84 Apr85 Oct8S May86 Oct86 May87 Oct87

Research Cruises

Figure 16a. Average temperature by area from research cruises.

• 100-120 fm 120-140 fmB 140+fmII

Apr82 Nov82 Nov83 May84 Oct84 Apr8S Oct8S May86 Oct86 May87 Oct87

Research Cruises

Figure 16b. Average temperature by depth from research cruises.