A stratified random bottom-trawl surveys on Flemish Cap was carried out in
July-August 1997 following the same method used since 1988. Results of shrimp
population (Pandalus borealis) are presented in this paper and compared with those
previously observed

Río-Iglesias, J.L. (José Luis) del

English

12 páginas, 4 figuras, 6 tablas.-- Scientific Council MeetingA stratified random bottom-trawl survey on Flemish Cap (NAFO Div. 3M) was carried out in July-August
1998 on board R/V Comide de Saavedra. The survey was conducted from July 17 to August 2 following the same
method used since 1988 and provided data on the distribution, abundance, biomass and demographic structure of
shrimp in the area. Results of shrimp population (Pandalus borealis) are presented in this paper and compared with
those previously observedPeer reviewe

Río, José Luis del

Digital.CSIC

Northern Shrimp (Pandalus borealis) on Flemish Cap in July-August 1998

Río-Iglesias, José Luis  del

Northern Shrimp (Pandalus borealis) on Flemish Cap in July-August 1997

8 páginas, 2 figuras, 5 tablas.-- Scientific Council MeetingPeer reviewe

NOT TO BE CITED WITHOUT PRIOR REFERENCE TO THE AUTHOR(S) Northwest Atlantic Serial No.N2934 Fisheries Organization NAFO SCR Doc. 97/88 SCIENTIFIC COUNCIL MEETING - SEPTEMBER 1997 Northern Shrimp (Pandalus borealis) on Flemish Cap in July-August 1997 by J. L. del Rio Institute de Investigaciones Marinas, Eduardo Cabello 6 36208 Vigo, Spain A stratified random bottom-trawl surveys on Flemish Cap was carried out in July-August 1997 following the same method used since 1988. Results of shrimp population (Pandalus borealis) are presented in this paper and compared with those previously observed. Material and methods The survey was conducted following the same procedures as in previous years (Vazquez, 1997). Samples of approximately one kilogram shrimp were taken in each tow this specie was present. Samples were frozen for posterior analysis. Males and females was separated according to the endopod of the first pleopod (Rasmussen, 1953). Individuals in the changing sex phase were included with males. Females were further separated as immatures (first time spawners) and matures (spawned previously) based on the condition of the sternal spines (McCrary, 1971). Oblique caparace length (CL): the distance from the base of the eye to the posterior dorsal edge of the caparace (Shumway et al, 1985) were measured to the lower 0.5 mm. 3318 individuals were weighed to the nearest 0.1 g after a little draining time to calculate the length-weight relationship. Results Total shrimp biomass estimated by swept area method and average catch per mile from 1988 to 1997 are presented in Table I. Biomass decreased from 6502 tons in 1996 to 5096 tons in 1997. Length frequencies and percentages by sex from 1997 survey are shown in Table 2. These length frequencies are split in males, immature females, mature females and ovigerous females. The increase in the frecuency of males observed during 1996 survey was followed in 1997 by a pronounced decrease (54.0% in 1996 and 36.3% in 1997). The 63.7% of individuals were females splited as: 34.7% immatures, 25.0% matures and 4.0% ovigerous. Percentage of immature females was 17.6% in the 1996 survey (del Rio, 1996), what indicated a notable increase of the immature group in 1997 compared with 1996. The spawing period in Flemish Cap begins between the end of July and the beginning of August (Mena, 1991). This year survey was carried out from July 16th to August 1st, taster in the season that in previous years, the percentage of ovigerous females was the higher observed since the surveys began. Males presented a CL between 13 and 26.5 mm. Females presented a CL between 17 and 32.5 mm comprising the groups: 18-30.5 mm immature, 17-32.5 mm mature and 20-32 mm ovigerous. 2 Length frequencies by strata in 1997 (Table 3) indicate that the presence of shrimp is scarce in depths lower than 257 m (140 fathoms) or higher than 554 m (301 fathoms). The shrimp mainly occupy those strata between 257 and 554 m, as in previous years. Minimum length observed was 13 mm CL in strata of depths lower than 360 m (200 fathoms), in those strata between 360 and 545 m (201-300 fathoms) it was 15.5 mm CL and in depths between 545 and 725 m (301-400 fathoms) it was 16 mm CL. This indicated that the minimum shrimp size increases with depth. Total biomass estimated by strata in 1997 (Table 4) shows a distribution pattern similar to that observed in 1996 survey in most of strata, and a sharp decrease in strata 14 and 15 (201 - 300 fathoms). Shrimp length distribution on Flemish Cap 1988-1997 are provided in Figure 1. It is assumed that modal groups named with the same letter belong to the same year-class. The reduction of biomass from 1996 to 1997 was mainly due to a decrease of abundance of modal group named 1 (19 - 22 mm CL) in 1996. All individuals of this year-class were males in 1996, when the mode was 20.5 mm CL (del Rio, 1996). Mean weight by length class of shrimp in years 1996 and 1997 were compared in Table 5; it was observed that shrimp weight decreases for all length-classes in 1997. The mean weight had increased in all length-classes from 1989 to 1992, in the period 1993-1996 the weigth only increases fot sizes greater than 27.5 mm CL (del Rio and Sainza, 1997). Catch distribution in kg/tow in the survey are provided in Figure 2. Catches do never exceeded 8 kg/tow in central and slope portions of the bank as is previous surveys, but there is a large area of low catches in the North of Flemish Cap, wider than observed in previous year. Few catches were higher than 20 kg/tow. References del Rio, J. L.- 1996. Northern Shrimp (Panda/us borealis) on Flemish Cap in July 1996. NAFO SCR Doc. 96/24, 10 pp. del Rio, 1. L. and Sainza, C.- 1997. Northern Shrimp (Panda/us borealis) Stock on Flemish Cap According to 1988-1996 surveys. NAFO SCR Doc. 97/ , 24 pp. McCrary, J. A.- 1971. Sternal spines as a characteristic for differentiating between females of some pandalidae. 1. Fish. Res. Bd. of Canada, 28: 98-100. Mena, I.- 1991. Northern prawn (Panda/us borealis) length distribution and fecundity in Flemish Cap. NAFO SCR Doc 91/29, 7 pp. Rasmussen, B.- 1953. On the geographical variation on growth and sexual development of the deep sea prawn (Panda/us borealis,Kroyer). Fish. Dir. Skr. Ser Hav Unders. 10 (3):pp 1-160. Shumway, S. E., H. C. Perkins, D. F. Schick and A. P. Stikney.- 1985. Synopsis of biological data on the Pink Shrimp (Pandalus borealis, Kroyer 1838). NOAA Techn. Rep. NMFS 30. 57 pp. Vazquez, A.- 1997. Results from bottom trawl survey of Flemish Cap in July 1996. NAFO SCR Doc 97/28. 30 pp. - 3 Table 1.- Total biomass estimated by swept area method and average catch per mile Year Biomass (t) Average catch per mile (Kg) 1088 2164 1.54 ± 0.28 1989 1923 1.37 ± 0.24 1990 2139 • 1.53 ± 0.21 1991 8211 5.83 ± 0.71 1992 16531 11.75 ± 1.86 1993 9256 6.57 ± 1.04 1994* 3337 2.37 ± 0.35 1995 5413 3.85 ± 0.44 1996 6502 4.62 ± 0.34 1997 5096 3.62 ± 0.25 cod-end mesh-size 40 mm - 4 Table 2.- Length frequencies and percentages by sex Length (mm) 	Males 	Immature 	Mature 	Ovigerous Females 	Females 	Females 13.0 7 13.5 46 14.0 122 14.5 70 15.0 95 15.5 155 16.0 257 16.5 137 17.0 299 9 17.5 324 18.0 744 1 18.5 1192 1 19.0 2258 13 19.5 2201 25 20.0 2321 70 ' 	1 4 20.5 1523 63 23 19 21.0 1304 317 63 2 21.5 1080 355 113 38 22.0 1381 783 345 71 22.5 1520 896 259 81 23.0 2442 2225 778 173 23.5 1485 2070 736 237 24.0 1557 3152 1145 456 24.5 642 3233 1210 . 246 25.0 294 3026 1521 	- 333 25.5 117 2438. 1480 284 26.0 79 1949 1826 212 26.5 6 1049 1643 165 27.0 627 1624 136 27.5 165 806 33 28.0 133 984 58 28.5 433 10 29.0 49 484 20 29.5 212. 2 30.0 237 30.5 1 138 31.0 95 2 31.5 84 3 32.0 - 	26 1 32.5  3 36.3% 34.7% 25.0% 4.0% frequency x 104 - 5 Table 3.- Lenght frequencies by strata STRATA Length 3 5 6 7 8 9 10 11 12 13 14 15 16 18 19 Total 13.0 7 7 13.5 7 5 10 4 20 46 14.0 7 11 11 54 • 14 25 122 14.5 7 10 1 17 2 34 70 15.0 16 1 19 9 25 25 95 15.5 22 1 39 14 13 43 14 9 155 16.0 13 15 3 85 22 13 30 55 11 5 6 257 16.5 10 19 . 	9 18 28 36 18 137 17.0 7 22 14 98 17 11 35 66 26 11 1 308 17.5 14 16 103 5 18 61 73 13 18 2 324 18.0 13 22 21 195 19 18 106 179 58 18 43 41 11 745 18.5 7 ,31 29 226 83 55 220 263 90 53 50 88 1193 19.0 20 .48 45 442 170 78 441 414 257 81 98 160 18 2271 19.5 20 50 34 315 138 108 414 386 179 179 144 199 34 1 24 2227 20.0 13 35 49 230 96 84 462 434 207 286 219 219 59 3 2396 20.5 27 33 12 89 110 71 341 201 165 162 141 142 42 1 92 1628 21.0 33 39 72 158 73 111 376 193 147 164 135 111 20 1 54 1686 21.5 27 28 54 170 50 167 348 124 255 124 92 72 27 1 47 1586 22.0 40 63 127 400 57 141 394 263 284 175 341 190 37 2 65 2580 22.5 20 75 81 207 113 184 578 331 389 118 283 204 75 4 96 2756 23.0 47 119 170 1041 246 283 872 608 774 259 351 380 111 6 354 5618 23.5 14 97 139 721 250 316 675 657 641 212 281 191 88 4 245 4528 24.0 7 83 145 1106 348 410 929 880 1199 315 222 218 90 5 355 6310 24.5 14 74 195 1020 396 265 829 711 908 270 105 296 53 6 197 5331 25.0 7 22 90 745 494 275 619 806 728 448 210 383 110 3 233 5174 25.5 33 49 516 300 205 439 648 854 432 189 283 97 2 275 4319 26.0 12 32 282 219 292 461 436 925 470 213 304 128 9 285 4066 26.5 4 14 203 63 162 292 358 629 334 150 292 81 5 274 2863 27.0 1 5 151 86 117 254 266 538 290 140 121 94 7 316 2387 27.5 5 10 41 38 119 116 306 58 44 85 54 6 121 1004 28.0 3 57 20 74 142 101 326 133 92 66 36 4 118 1175 28.5 2 28 31 48 37 102 29 25 47 24 3 67 443 29.0 3 13 18 36 46 76 110 47 42 56 38 2 67 553 29.5 1 26 23 39 11 22 5 17 2 68 214 30.0 7 6 35 26 36 40 32 5 31 20 237 30.5 1 3 14 26 32 22 16 3 10 11 139 31.0 3 14 13 16 12 11 6 6 17 97 31.5 5 14 42 14 13 87 32.0 6 11 2 6 3 27 32.5 2 1 3 frequency x 10° - 6 Table 4.- Total biomass estimated by strata (tons) Stratum Depth 1988 1989 1990 1991 1992 .1993 1994 . 1995 1996 1997 (fathoms) 1 70-80 0 0 0 0 0 0 0 0 0 0 2 81-100 0 0 0 0 0 0 0 162 0 0 3 101-140 0 0 0 5 0 1 0 2 86 21 4 101-140 0 0 0 0 0 0 0. 0 0 0 5 101-140 0 0 0 4 8 0 0 6 12 57 6 101-140 0 0 2 19 3 3 0 11 94 111 7 141-200 18 20 212 713 2134 1404 93 299 684 637 8 141-200 9 51 46 158 1130 545 3 183 412 269 9 141-200 57 47 24 150 88 109 0 506 324 287 10 141-200 115 44 188 1499 2278 972 658 873 707 706 11 141-200 89 0 105 733 2714 794 358 452 699 669 12 201-300 786 582 313 1733 3329 1786 599 778 910 871 13 201-300 64 58 42 63 28 120 0 28 416 394 14 201-300 255 218 407 814 1640 1161 556 632 706 286 15 201-300 404 328 558 1485 2522 2029 916 1021 922 332 16 301-400 308 234 239 171 303 133 44 47 148 121 17 301-400 2 10 0 0 0 0 0 0 0 1 18 301-400 0 0 0 0 0 0. 0 1 30 8 19 301-400 56 331 4 663 354 163 111 412 351 327 Total: 2164 1923 2139 8211 16531 9256 3337 5413 6502 5096 Table 5. - Mean weight and length class in year 1996 and 1997 Length (mm) Mean weight (g) 1996 1997 10.0 0.6 0.5 12.5 1.1 1.1 15.0 2.0 1.9 17.5 3.2 3.0 20.0 4.8 . 4.5 22.5 6.9 6.4 25.0 9.5 8.8 27.5 12.7 11.7 30.0 16.6 15.3 32.5 21.2 19.5 35.0 26.6 24:4 Males Females Total 200 uto eo ea 250 1988 2o B A C B 12 14 10 18 20 22 12 14 16 18 20 22 24 20 0 30 32 34 	12 14 18 18 32 2 04 te 	za 22 24 28 2e 30 150 100 150 100 40 C 	B 	50 0 	 0 11 14 113 10 20 22 24 211 25 30 32 14 	12 14 10 10 100 ea ea 160 ea 22 24 26 20 30 32 34 1989 26 30 103 00 ea 40 20 2 14 16 18 20 22 14 34 CO - 20-00 -20 0 12 14 16 18 20 22 24 20 20 30 32 34 100 120 80 0 12 14 18 16 20 22 24 26 10 30 32 12 14 II 18 20 22 24 34 	11 14 16 10 20 22 24 28 20 30 32 34 2 14 IS 10 20 E 12 14 11 13 20 22 24 211 20 30 32 34 	12 14 11 18 20 22 24 21 10 30 32 34 12 14 18 18 20 22 24 20 28 30 32 34 IW eo 80 100 eo eo 40 20 0 12 14 10 18 20 22 24 20 28 30 32 34 40 0  12 14 18 00 20 22 24 21 28 30 32 0 34 	12 14 68 18 20 22 24 20 10 30 32 34 200 120 80 40 0 	  12 04 18 113 20 22 24 26 211 30 32 34 	12 04 18 18 20 22 24 28 21 30 32 34 200 150 1123 11 	G 1993 1994 100 	 20 	 2 eo eo 40 22 24 28 211 30 32 34 K J L 0 12 14 10 IS 20 22 24 20 113 30 32 12 14 83 18 20 22 24 26 28 38 32 34 	12 14 Id 111 20 22 24 20 21 30 31 34 183 80 ea 40 10 PMI 8 8 8 8°  MIi § F F. s  °  WO 18  8 8 9 00 ; wo a 24 28 78 30 32 34 	12 14 10 10 20 22 24 	28 311 32 34 	12 14 18 18 20 22 24 211 21 30 32 34 100 00 80 20 0 12 14 IS 18 20 Figure 1.- Shrimp length distribution on Flemish Cap 1988 -1997 surveys 	1-Axis = Frequency ( 108 ) X-Axis = Length ( mm) 0 0 co 0 0 - 8 46° 00' 	 45° 00' 	 44° 00' 46° 00' 	 45 00' 	 44° 00' CO 0 0 0 0 0 Figure 2 .- Shrimp catch (Kg/tow) distribution in July 1997 on Flemish Cap. 

Repositorio Institucional Digital del IEO

A stratified random bottom-trawl survey on Flemish Cap (NAFO Div. 3M) was carried out in July-August
1998 on board R/V Comide de Saavedra. The survey was conducted from July 17 to August 2 following the same
method used since 1988 and provided data on the distribution, abundance, biomass and demographic structure of
shrimp in the area. Results of shrimp population (Pandalus borealis) are presented in this paper and compared with
those previously observed

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Northern Shrimp (Pandalus borealis) on Flemish Cap in July-August 1997

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