Journal of the Marine Biological Association of the United Kingdom cambridge.org/mbi Original Article Cite this article: Kouamé KYN, Konan KJ, Ouattara NI, Koné T (2019). Aspects of the reproductive biology of the blue shark Prionace glauca (Linnaeus, 1758) in the coastal waters of Ivory Coast, West Africa. Journal of the Marine Biological Association of the United Kingdom 99, 1435–1441. https://doi.org/ 10.1017/S0025315419000274 Received: 23 July 2018 Revised: 21 February 2019 Accepted: 21 March 2019 First published online: 17 April 2019 Key words: Atlantic Ocean; blue shark; fecundity; reproductive biology; sex ratio; West Africa Author for correspondence: Kouadio Justin Konan, E-mail: konankouadjustin@yahoo.fr © Marine Biological Association of the United Kingdom 2019 Aspects of the reproductive biology of the blue shark Prionace glauca (Linnaeus, 1758) in the coastal waters of Ivory Coast, West Africa Kouassi Yves Narcisse Kouamé 1 , Kouadio Justin Konan 2 , Nahoua Issa Ouattara 1 and Tidiani Koné 3 1 Laboratoire d’Hydrobiologie, UFR Biosciences, Université Félix Houphouët-Boigny, 22 BP 582 Abidjan 22, Côte d’Ivoire; 2 Centre de Recherches Océanologiques, BP V 18 Abidjan, Côte d’Ivoire and 3 UFR Environnement, Université Jean Lorougnon Guédé, BP 150 Daloa, Côte d’Ivoire Abstract The blue shark Prionace glauca is the most abundant species in the artisanal driftnet fishery off the coastal waters of Ivory Coast. The reproductive parameters were investigated with the aim of providing basic information on the reproductive biology for fisheries management. A total of 424 specimens (256 males and 168 females) ranging from 170–330 cm in total length (TL) were sampled between August 2014 and November 2016. Sample for embryonic sex ratio was obtained from 18 litters of 503 individuals (255 males and 248 females). The embryonic sex ratio was not significantly different from 1:1 (χ 2 = 0.10, P > 0.05, N = 503). The size at 50% maturity (L 50 ) was 218.1 cm TL for males and 223.3 cm TL for females. The litter size based on the number of embryos varied from 6 to 62, with an average of 30 embryos. Mating started in July whereas ovulation, fertilization and uterine eggs occurred in late October–November. Smallest embryos of 3–5 cm in stretch total length (STL) appeared in uterus from November to January. The embryo size varied widely among months, and well-pigmented embryos were already present in April–May samples, although most of them occurred in August–September, suggesting a gestation period of around 11 months. The absence of neonates in catches, as well as parturition females, does not support a hypothesis that parturition takes place in the Gulf of Guinea. Introduction The blue shark Prionace glauca (Linnaeus, 1758) is a large pelagic Carcharhinid, widely dis- tributed in temperate and tropical waters (Compagno et al., 2005; Hazin & Lessa, 2005). Its distribution and movements are strongly influenced by seasonal variation of water tempera- ture, reproductive condition and availability of prey (Nakano, 1994; Nakano & Stevens, 2008). This species is mainly captured by tuna longline and driftnet fisheries as a target or by-catch species (Nakano & Stevens, 2008). There is a growing concern over the impact of commercial fisheries on this species and the effects on the oceanic ecosystem of major reduc- tions in their abundance (Stevens et al., 2010). According to Froese & Pauly (2005), the impact of fisheries on blue shark annual mortality (mainly by-catch) has been estimated at 10–20 million individuals, which could have a marked effect on the world population. Knowledge of the reproductive aspects of exploited species is essential for the sustainable management of fisheries since these parameters are used to estimate productivity and rebound potential of a fish stock in assessment models (Baremore & Passerotti, 2013). Given its abun- dance, distribution range and commercial importance, the reproduction biology of P. glauca has been extensively studied (Pratt, 1979; Francis & Duffy, 2005; Megalofonou et al., 2009; Zhu et al., 2011; Jolly et al., 2013; Montealegre-Quijano et al., 2014; Fujinami et al., 2017) as well as its distribution patterns and population structure in different oceans (Mejuto & García-Cortés, 2005; Coelho et al., 2018). Despite its importance in catches (Clarke et al., 2006), no published works exist on its reproductive biology in the central eastern Atlantic, except that of Castro & Mejuto (1995) in the Gulf of Guinea. In Ivory Coast, the available works are restricted to N’Goran & Amon-Kothias (2002), N’Goran et al.(2005) and Konan et al.(2014) on abundance and catch composition. The aim of the present study was to deter- mine the reproductive parameters of P. glauca caught in the central eastern Atlantic by the artisanal driftnet fishery of Ivory Coast. Materials and methods Sampling and data collection Samples of Prionace glauca used for this study were collected from commercial catches at the fishing harbour of Abidjan from the artisanal driftnet fishery targeting tuna species, which operated between latitudes 4°N and 5°N and longitudes 2.30°W and 8°W (Figure 1). The specimens were sampled monthly from August 2014 to November 2016. https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0025315419000274 Downloaded from https://www.cambridge.org/core. IP address: 207.241.231.108, on 11 Mar 2020 at 11:52:36, subject to the Cambridge Core terms of use, available at