Maturity and Other Biological Aspects of Main Deep-Water Squaloid Sharks, in the North and Northwest of the Iberian Peninsula (ICES Divisions Viiic, Ixa and Ixb)

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Northwest Atlantic Fisheries Organization

Serial No. N4509 NAFO SCR Doc. 01/121

SCIENTIFIC COUNCIL MEETING – SEPTEMBER 2001 (Deep-sea Fisheries Symposium – Poster)

Maturity and Other Biological Aspects of Main Deep-water Squaloid Sharks, in the North and Northwest of the Iberian Peninsula (ICES Divisions VIIIc, IXa and IXb)

José Miguel Casas, Carmen Piñeiro and Rafael Bañón. Centro Oceangráfico de Vigo (IEO), Apdo. 1552, Vigo, Spain http://www.ieo.es

Abstract

The aim of this poster is to compile different information concerning some biological aspects of deep-water sharks captured during between 500 and 1300 m depth off the continental slope in the north and northwest of the Iberian Peninsula (ICES Division VIIIc, IXa and IXb).

The catches and yields of the different deep water squaloid sharks (Centrophorus squamosus, Centrophorus granulosus, Centroscymnus coelolepis, Deania calceus and Scimnodon ringen) are reported as well as other aspects concerning their depth distribution, length distribution, sex ratio, length-weight relationship, fecundity and maturity.

Introduction

For the purpose of this study deep-water sharks are defined as demersal or benthopelagic sharks which inhabit at depths greater than 400 m. Data on specific deep-water sharks is scarce in the north and northwest of the Iberian Peninsula because the small fisheries developed with a notable local and seasonal character.

The aim of this study is to report the available information concerning deep-water sharks, their depth distribution and the main biological aspects obtained in commercial fisheries and exploratory surveys.

Material and Methods

Specimens were captured between 500 and 1300 m depth off the continental slope in the north and northwest of the Iberian Peninsula (ICES Division VIIIc, IXa and IXb) during two experimental surveys carried on commercial vessels (bottom trawlers and longliners). Additional information was provided by samplings conducted from 1996 to 1998 on board longliners from commercial fishery (Table 1, Fig. 1 and 2).

Length and depth distribution by sex of the main deep water squaloid sharks (Centrophorus squamosus, Centrophorus granulosus, Centroscymnus coelolepis, Deania calceus and Scymnodon ringens) are shown as well as the main biological aspects concerning to sex ratio, length-weight relationship, fecundity and maturity.

Length measurements (from the tip of the snout to the tip of the upper lobe of the caudal fin) were taken to the nearest centimetre and grouped by 3-cm length class.

Maturity was determined following the scale described by Stehmann (1987). This scale is based on macroscopic aspects: for mature males with claspers fully formed and stiff. For mature females with large ovaries, well rounded and the oocytes all to about the same size can easily be counted. 2

Ovarian fecundity was estimated by counting the number the ova in ripe females. Similarly uterine fecundity was determined from pregnant females with embryos more or less fully formed, pigmented and yolk sacks reduced. The size at birth was estimated by measuring the embryos without yolk.

Results

In general the female length range and size were greater than males in all species here considered. With the exceptions of D. calceus and S. ringens, the specimens smaller than 70 cm were absent in the catches (Table 2).

The sex-ratio varied along the different species, highlighting C. granulosus and C. coelolepis where the most part of the specimens were females (higher than 90%). On the other side, the males of C. squamosus were the predominant (up to 83%). D. Calceus and S. ringens showed different sex-ratio in relation with the gear used (close to 50% in bottom trawlers and greater presence of females in long liners (around of 80%) (Table 2).

The analysis of depth distribution from the species here studied was difficult due to the different gears used and different objectives of the vessels sampled (commercial or exploratory fishing surveys), (Fig. 3). However in general S. ringens and D. calceus presented a depth distribution shallower than the C. granulosus, C. squamosus and C. coelolepis.

The length-weight relationship showed for all species a R2 > 0.8. (Fig. 4)

The percentage of maturity by sex, size at first maturity (L50), the ovarian fecundity, uterine fecundity and size at birth are shown in tables 3 and 4. From some species, the small number of mature and immature individuals in the catches (S. ringens and C. coelolepis respectively) as well as the absence of a sex (C. granulosus) did not permit the estimation of these parameters. Moreover the percentage of maturity by sex and length class and the maturity ogives (adjusted by the method of maximum likelihood) were plotted whenever was possible (Fig. 5).

Discussion

The different objectives in the vessels sampled (commercial or exploratory fishing surveys) and the different gears used make difficult to compare the length and depth distribution in the study areas (Fig. 4).

The absence of small specimens in the catches of genus Centrophorus and Centroscymnus in both type of vessels (bottom trawlers and longliners) is an aspect pointed out by other authors (Conolly and Kelly, 1997; Kelly et. al., 1997). However the presence of pregnant females, close to the extruding (embryos without yolk), it would indicate a different pattern distribution of the smallest specimens at greater depths (Girard and Du Buit, 1998). However this hypothesis must be confirmed.

The size at first maturity in sharks is usually greater for females than males. Nevertheless the absence of adequate samplings scheme by sex in some of the studied species does not permit to analyse this aspect.

References

Conolly, P., and C. Kelly. 1997. Deep water trawl and longline surveys in 1995. Fisheries Research Centre, Dublin, 173, 20p. Girard, M., and M.-H. Du Buit, 1999. Reproductive biology of two deep-water sharks from the British Isles, Centroscymnus coelolepis and Centrophorus squamosus (Chondrichthyes: Squalidae). J. Mar. Biol. Ass. U.K. 79. 923-931. Kelly, C., M. Clark, and P. Connolly. 1997. Catch and discards from a deep-water trawl survey in 1996. Fisheries Research Centre, Dublin, 175, 16p. Stehmann, M. 1987. Quick and dirty tabulation of stomach contents and maturity stages for skates Rajidae, squaloid and other ovoviviparous and viviparous species of sharks. American Elasmobranch Society Newslwtter. No.3, 5-9. 3

Table 1.- Exploratory surveys and commercial vessels from which data were obtained.

N- hauls Depth Range Ship Survey Type Zone Gear Date Code (N-hooks) (m.) VIIIc Jul-Sep-96 TE-VIIIc 75 512-1244 Playa de Montalvo Exploratory Trawl IXa Jul-Sep-96 TE-IXa 39 640-1171 VIIIc Jul-Sep-96 TE-VIIIc 78 580-1372 Mar de Marín Exploratory Trawl IXa Jul-Sep-96 TE-IXa 38 646-1098 IXa April-97 L2C-IXa 1 (2880) 1163 Commercial Longline Elenita2T IXb April-97 L2C-IXb 3 (5760) 1041-1145 VIIIc April-97 L2C-VIIIc 3 (8640) 1116-1165 La Polar Commercial VIIIc Longline June-97 L2C-VIIIc 1 (2000) 983 Playa del Rosal Commercial VIIIc Longline June-97 L2C-VIIIc 2 (4000) 732-769 IXb August-97 21 (19200) 725-860 Exploratory Longline L1E-IXb Coruxo IXb October-97 15 (16000) 659-805 IXb April-98 10 (12800) 686-858 IXb August-97 36 (15175) 686-1116 Exploratory Longline L2E-IXb María Rosa IXb October-97 15 (12100) 952-1072 IXb April-98 10 (9600) 946-1052 Elenita4T Commercial VIIIc Longline Nov-Dec-97 L2C-VIIIc 5 (10000) 1043-1208

Table 2.- Length range, mode length, mean length (cm) and sex-ratio from deep-water sharks species by sex, type of gear and Division.

Deania calceus Divisions VIIIc + IXa IXb Survey type Expl.-Trawl Comm.-Longline Expl.-Longline males females males females males females Min-length 24 24 72 66 60 66 Max-length 102 117 111 114 93 117 Mode Length 84 105 84 102 84 90 Mean length 73 89 85 96 83 92 Sex ratio % 52.5 47.5 36.0 64.0 27.9 72.1 Number 777 702 300 533 106 274

Scymnodon ringens Divisions VIIIc + IXa IXb Survey type Expl.-Trawl Expl.-Longline males females males females Min-length 33 33 42 42 Max-length 78 105 72 111 Length Mode 72 39 69 81 Mean length 54 59 63 85 Sex ratio % 49.3 50.7 19.3 80.7 Number 176 181 17 71

Centroscymnus coelolepis Divisions VIIIc + IXa IXb Survey type Comm.-Longline Expl.-Longline Comm.-Longline males females males females females Min-length 96 105 87 93 102 Max-length 96 117 99 120 117 Length Mode 96 111 93 111 111 Mean length 96 111 92 110 111 Sex ratio % 1.5 98.5 10.3 89.7 100.0 Number 1 64 30 260 38

Centrophorus granulosus Divisions IXb Survey type Comm.-Longline Expl.-Longline males females males females Min-length 111 111 114 108 Max-length 111 159 114 165 Length Mode 111 141 114 153 Mean length 111 136 114 146 Sex ratio % 1.4 98.6 0.9 99.1 Number 1 69 2 216

Centrophorus squamosus Divisions VIIIc + IXa IXb Survey type Comm.-Longline Comm.-Longline Expl.-Longline males females males females males females Min-length 87 87 87 102 87 96 Max-length 120 138 120 135 129 144 Length Mode 111 105 111 126 111 132 Mean length 109 115 110 124 83 92 Sex ratio % 75.6 24.4 83.0 17.0 83.1 16.9 Number 685 221 186 38 1015 207 5

Table 3.- Percentage by sex, and size at the first maturity (L50) of the caught specimens.

Sample size (number) % of mature L50 of maturity Species males females males females males females C. squamosus 1265 272 95% 30% 98.5 127.0 C. granulosus 10 157 30% 52% 144.2 C. coelolepis 28 253 57% 98% D. calceus 380 614 56% 43% 79.8 98.6 S. ringens 70 140 6% 11%

Table 4.- Ovarian fecundity (number of mature ova in ripe females), uterine fecundity (number of embryos in pregnant females) and size to birth of the studied species.

Ovarian fecundity Uterin Fecundity Size to born Sampled Species Mean ova/female Mean embryos/female Specimens Range Average size (range) (range) C. squamosus 8 9 (7-12) 7 38-40 39.1 C. granulosus 39 5 (10-2) 3 (1-6) 35-42 39.9 C. coelolepis 52 - 14(5-22) 27-29 27.9 D. calceus 27 12 (8-19) 8 (2-13) 28-40 34.5 S. ringens 3 8 (7-8) - - -

Figure 1.-Chart with the areas sampled along continental slope of ICES Divisions VIIIc, IXa and IXb

FRANCE

VIIIc

IXa IXb SPAIN

PORTUGAL

Fig. 1.- Chart with the area sampled along continental slope of ICES Divisions VIIIc, IXa and Ixb.

Bottom trawl using during exploratory survey in ICES Division VIIIc and IXa

Longline used in exploratory surveys (L1) in depths lesser than 800 meters

Longline used in exploratory surveys and comercial fisheries (L2) in depths greater than 800 meters.

Fig. 2.- Gears used in Exploratory and Commercial fisheries.

Deania calceus Scymnodon ringens Centroscymnus coelolepis

Box & Whisker Plot: AV_DEPTH 1300 Box & Whisker Plot: AV_DEPTH Box & Whisker Plot: AV_DEPTH 1300 1300 1200 1200 1200 1100 1100 1100 1000 1000 1000 900 900 900

800 AV_DEPTH 800 800 AV_DEPTH 700 700 AV_DEPTH 700

600 600 600 Min-Max 500 500 500 25%-75% TE-IXa-m TE-VIII1 L2C-VII1 L2E-IXb1 Min-Max Min-Max TE-IXa-f TE-VIIIc L2C-VIII L2E-IXb- Median value 400 25%-75% 400 25%-75% TE-8CM TE-IXaM L2E-IXbM TE-VIIIc-m TE-IXa-m L2E-IXb-m SV_CODE Median value TE-8CF TE-IXaF L2E-IXbF TE-VIIIc-f TE-IXa-f L2E-IXb-f Median value SV_CODE SV_CODE

Centrophorus granulosus Centrophorus squamosus

Box & Whisker Plot: AV_DEPTH Box & Whisker Plot: AV_DEPTH 1200 1300

1160 1200

1120 1100 1080

1000 1040 AV_DEPTH 1000 AV_DEPTH 900 960 800 920 Min-Max Min-Max 25%-75% 700 25%-75% 880 L2C-IXbF L2E-IXbF L2C-8CF L2C-IXbF L2E-IXbF Median value L2C-IXbM L2E-IXBM L2C-8CM Median value SV_CODE SV_CODE

Fig. 3.- Depth distribution by sex, area, gear type and activity (TE: Botton Trawl Exploratory; L2C: Longline directed to deep-water sharks from Commercial Fisheries; L2E: Longline directed to deep-water sharks from Exploratory Surveys).

Deania calceus Scymnodon ringens Centroscymnus coelolepis

10000 14000 18000

3.4 158 3.8 188 3 .0 841 16000 y = 0.0007x y = 0.005x y = 0.0002x 2 12000 2 R = 0.9425 2 R = 0.8064 8000 R = 0.9702 14000 10000 12000 6000 8000 10000

6000 8000 4000 6000 4000 4000 2000 2000 2000 N=973 N=304 0 0 0 80 90 100 110 120 130 30 40 50 60 70 80 90 100 110 120 25 35 45 55 65 75 85 95 105 115 TL (cm) TL (cm) TL (cm) Centrophorus granulosus Centrophorus squamosus

40000 25000 3.7225 3.65 54 35000 y = 0.0002x y = 0.0002x 2 R = 0.9213 20000 R2 = 0.8276 30000

25000 15000 20000 15000 10000 10000 5000 5000

0 0 90 100 110 120 130 140 150 160 170 70 80 90 100 110 120 130 140 150

TL (cm) TL (cm)

Fig. 4.- Length-weight relationships for both sexes and different areas joined.

Maturity o jive from females o f D.calceus Maturity ojive from males of 100% 100% observeb predicted P-observed P-predicted 75% 75%

50% 50%

25% 25% N=612 N=377 0% 0% 52 58 64 70 76 82 88 94 100 106 112 TL (cm) 46 52 58 64 70 76 82 88 94 100 109 115 TL (cm)

Maturity o jive from females of C. granulosus 100%

observed predicted 75%

50%

25% N=153

0% 106 112 118 124 130 136 142 148 154 160 166 TL cm

Matu rity ojive from females of C. squ amosus Maturity ojive from males of C. squamosus

100% 100%

observed predicted observed predicted 75% 75%

50% 50%

25% 25% N=272 N=1264

0% 0% 86 95 101 107 113 119 125 131 137 143 86 92 98 104 110 116 122 128 TL (cm) TL (cm)

Fig. 5.- Maturity ogives from the species studied.