Reproductive ecology of demersal elasmobranchs from a data-deficient fishery, Pacific of Costa Rica, Central America

Fisheries Research 157 (2014) 96–105

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Reproductive ecology of demersal elasmobranchs from a data-deficient fishery, Pacific of Costa Rica, Central America Tayler M. Clarke a,b,∗ , Mario Espinoza b,c,d , Ingo S. Wehrtmann b,c a Programa Gestión Integrada de Áreas Costeras Tropicales (GIACT), Centro de Investigación en Ciencias del Mar y Limnología (CIMAR), Universidad de Costa Rica, 11501-2060 San José, Costa Rica b Unidad de Investigación Pesquera y Acuicultura (UNIP) of the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR), Universidad de Costa Rica, 11501-2060 San José, Costa Rica c Escuela de Biología, Universidad de Costa Rica, 11501-2060 San José, Costa Rica d Centre for Sustainable Tropical Fisheries and Aquaculture, School of Earth and Environmental Sciences, James Cook University, Townsville, QLD 4811, Australia

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Article history: Received 10 November 2013 Received in revised form 31 March 2014 Accepted 3 April 2014 Handling Editor A.E. Punt Keywords: Sharks and rays Size at maturity Segregation Critical habitats Eastern Tropical Pacific

a b s t r a c t The elasmobranch bycatch associated with the Costa Rican deepwater shrimp fishery is mainly comprised of four species: Raja velezi, Mustelus henlei, Zapteryx xyster and Torpedo peruana. In data-deficient fisheries such as this one, knowledge of the reproductive ecology of a species may serve as a valuable management tool to determine its vulnerability and apply precautionary measures to ensure its long-term conservation. This study examined the reproductive ecology of R. velezi, M. henlei, Z. xyster and T. peruana based on data collected during demersal trawling along the Pacific coast of Costa Rica, Central America. A total of 290 trawls was analyzed at depths of 18–350 m (March 2010–August 2012). While R. velezi, M. henlei and Z. xyster matured at similar sizes (range: 37–60 cm TL), T. peruana matured at a larger size (70 cm TL in females). The four elasmobranch species exhibited strong sex and size segregation patterns, which were mainly influenced by depth. Adults were more common at depths >50 m, whereas neonates and gravid females were more abundant in shallow estuarine waters (100 m (Table 1). Overall, a sample of 3762 elasmobranchs from 23 species and 13 families was obtained, of which 1851 specimens belonged to the four studied species. Raja velezi was the most abundant species in trawl catches (38.2%), followed by M. henlei (30.0%), Z. xyster (21.2%), and T. peruana (10.6%) (Table 2). Raja velezi, M. henlei and T. peruana were caught throughout the sampled depth range, while Z. xyster was rare at depths >100 m. The minimum size of the four studied species varied from 13.2 to 21.8 cm TL; the smallest specimen was of R. velezi. The maximum observed sizes of all species ranged between 66.5 and 88.9 cm TL (Table 2). Torpedo peruana attained the largest size with 88.9 cm TL, followed by R. velezi with 85.6 cm TL (Table 2). 3.1. Size at maturity Most of the examined R. velezi had small or large sizes, intermediate-sized R. velezi were nearly absent from the samples (Fig. 2a and b). Overall, 59% of female and 62% of male R. velezi were classified as mature (Fig. 2a and b, Table 3). Females matured at 53.0–58.0 cm TL, while males reached maturity at 57.5–60.5 cm TL (Table 3). In M. henlei, 42% of all females and 79% of all males were mature (Fig. 2d and c). Females matured at 41.0–44.0 cm TL and males at 36.0–39.0 cm TL (Table 3). In Z. xyster, most females were mature (59%), while most males were immature (56%) (Fig. 2f and e, Table 3). The size at maturity for female Z. xyster was estimated at 47.0–52.0 cm TL and for males at 42.0–47.0 cm TL (Table 3). The Table 2 Abundance and size (minimum, maximum and mean total length – TL – cm) of Raja velezi, Mustelus henlei, Zapteryx xyster and Torpedo peruana captured along the Pacific coast of Costa Rica, Central America (March 2010–August 2012). Species

Size

100 m

Raja velezi

N Max. TL Mean TL ± S.E. Min. TL

1 65.8 65.8 65.8

141 85.6 46.1 ± 1.0 13.2

566 76.4 66.1 ± 0.6 24.7

Mustelus henlei

N Max. TL Mean TL ± S.E. Min. TL

10 52.3 48.4 ± 0.9 42.7

384 66.5 41.8 ± 0.5 21.8

161 63.6 44.6 ± 0.5 25.5

Torpedo peruana

N Max. TL Mean TL ± S.E. Min. TL

5 55.9 31.3 ± 7.5 15.4

71 90.0 42.2 ± 2.0 14.2

120 88.9 46.7 ± 0.9 21.6

Zapteryx xyster

N Max. TL Mean TL ± S.E. Min. TL

60 78.3 32.0 ± 2.3 15.6

327 70.7 44.7 ± 0.9 15.1

5 66.2 52.4 ± 4.6 41.8

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Fig. 2. Maturity ogives for Raja velezi (males (a) and females (b)). Mustelus henlei (males (c) and females (d)), Zapteryx xyster (males (e) and females (f)) and Torpedo peruana (males (g) and females (h)). Histograms display the sample size structure, black portions represent immature individuals while gray portions represent mature individuals.

majority of female (96%) and male (80%) T. peruana were immature (Fig. 2h and g; Table 3). Females reached their size at maturity at 66.0–75.0 cm TL, while males matured at 52.0–55.5 cm TL (Table 3). The size of gravid female R. velezi (N = 20) ranged from 60.6 to 76.9 cm TL and had up to two egg capsules at a time. Gravid females

of M. henlei (N = 33) ranged from 46.5 to 66.5 cm TL and had litter sizes of 1–12 embryos (Fig. 3). A positive linear relationship was found between female size and litter size in M. henlei (Fig. 3). Size of gravid female Z. xyster (N = 5) ranged from 39.6 to 64.0 cm TL, with litter sizes that varied between one and eight embryos. Gravid female T. peruana were not observed during the study period.

Table 3 Maturity curve parameters for males and females of Raja velezi, Mustelus henlei, Zapteryx xyster and Torpedo peruana from the Pacific coast of Costa Rica. The 95% confidence interval for the maturity size is also presented. Raja velezi

Maturity interval Maturity size (cm) B A

Mustelus henlei

Zapteryx xyster

Torpedo peruana

Male (N = 185)

Female (N = 199)

Male (N = 293)

Female (N = 133)

Male (N = 141)

Female (N = 251)

Male (N = 81)

Female (N = 97)

57.5–60.5 59.5 −0.7 40.3

53.0–58.0 55.8 −0.3 17.4

36.0–39.0 37.2 −0.3 12.1

41.0–44.0 39.7 −0.6 23.1

42.0–47.0 44.5 −0.3 11.2

47.0–52.0 43.0 −0.6 25.1

52.0–55.5 53.3 −0.8 42.3

66.0–75.0 69.7 −0.4 28.0

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T.M. Clarke et al. / Fisheries Research 157 (2014) 96–105

Fig. 3. Relationship between the number of embryos and the total length of the females and litter size of Mustelus henlei (a; r2 = 0.79, y = 19.8058 + 0.4630x; N = 33).

3.2. Spatial and seasonal segregation patterns Evidence of segregation by sex was observed in R. velezi, M. henlei and Z. xyster (Table 4). Male R. velezi and M. henlei were more abundant in deeper waters, while in Z. xyster, females dominated at intermediate depths. In contrast, T. peruana did not differ from a 1:1 sex ratio at any depth. The distribution of immature and mature individuals for the four studied species also varied by depth (Table 4). A greater proportion of mature R. velezi was observed at depths >100 m, while immature stages of Z. xyster dominated in shallower waters (