Journal of the Marine Biological Association of the United Kingdom, 2016, 96(4), 869–875. # Marine Biological Association of the United Kingdom, 2015 doi:10.1017/S0025315415001538 Stomach contents of by-caught striped dolphins (Stenella coeruleoalba) in the eastern Mediterranean Sea ayhan dede1,2, alp salman3 and arda m. tonay1,2 1Faculty of Fisheries, Istanbul University, Ordu Cad. No: 200 Laleli, Istanbul, Turkey, 2Turkish Marine Research Foundation (TUDAV), P.O. Box: 10 Beykoz, Istanbul, Turkey, 3Faculty of Fisheries, Ege University, Bornova, Izmir, Turkey Stomach contents of six striped dolphins taken as by-catch in the swordfish fishery in the eastern Mediterranean Sea off the Turkish coast were examined. In total, 29 taxa were identified to species or family and 1777 individual food items (1394 bony fishes, 289 cephalopods, 94 crustaceans) were counted. Diaphus spp. and Ceratoscopelus maderensis were the most remark- able ones, as they accounted for 70.45% of the total number of fishes. Onychoteuthis banksii, on the other hand, was the only cephalopod species found in all stomach content analyses and represented 38.06% of the total number of cephalopods. Bony fish species: Myctophum punctatum, Notoscopelus elongatus, Electrona risso, Sudis hyalina, Moridae sp., Phycidae sp., Sternoptychidae sp. and cephalopods: Pterygioteuthis giardi and Chtenopteryx sicula were reported the first time in the stomach contents of striped dolphin in the Mediterranean Sea. Keywords: Cetacea, striped dolphin, Stenella coeruleoalba, stomach content, eastern Mediterranean Submitted 11 July 2015; accepted 23 August 2015; first published online 28 September 2015 INTRODUCTION in various fishing gears, such as driftnets in the Aegean and the Mediterranean Sea. There have been several incidents of The striped dolphin (Stenella coeruleoalba) is widely distribu- striped dolphin by-catches in the swordfish driftnet fishery ted in temperate to tropical seas worldwide and is the most in the Turkish waters before (O¨ ztu¨rk et al., 2001; Akyol common cetacean species in the Mediterranean, found in off- et al., 2005; Dede, 2008) until this particular fishery method shore water from Gibraltar to the Levant Basin and the was banned in 2006. Aegean Sea (Jefferson et al., 1993; Notarbartolo di Sciara & The aim of this study is to better understand feeding pre- Birkun, 2010). There are also some stranding and live sight- ferences of striped dolphins with more samples in the ings records in the Marmara Sea (O¨ ztu¨rk et al., 1999; Altug˘ Turkish coastal waters of the eastern Mediterranean Sea. et al., 2011). The Mediterranean subpopulation is classified by IUCN as vulnerable (Aguilar & Gaspari, 2012). The species is typically oceanic, inhabiting deep waters beyond MATERIALS AND METHODS the continental shelf (Notarbartolo di Sciara et al., 1993; Forcada et al., 1994; Gannier, 2005), where it feeds primarily The samples were collected in the Turkish coast of the eastern on mesopelagic fish and cephalopods, and crustaceans to a Mediterranean Sea (Dede, 2008), between Fethiye and Kalkan lesser extent (Wu¨rtz & Marrale, 1993). In addition, they are (Figure 1), in June 2003 and 2004. Six striped dolphins acci- recorded in shallow waters and feeding on demersal or dentally entangled in the swordfish driftnets were examined coastal fish species (Frantzis et al., 2003; Spitz et al., 2006; (Table 1). The distance from the coast was 7–9 nautical Santos et al., 2008). But typically, prey organisms are small- miles. The four animals from sampling area 2 were caught sized, pelagic, schooling and vertically migrating species by the same driftnet. All the animals were measured and the (Ringelstein et al., 2006; Meissner et al., 2012). stomachs were sampled and stored in a freezer at 2208C. The diet of the striped dolphin is well documented in the Samples were thawed in the laboratory, the contents western and central Mediterranean Sea (Pulcini et al., 1992; removed, washed and sieved in a 200 mm mesh size sieve Bello, 1993;Wu¨rtz & Marrale, 1993; Blanco et al., 1995; and stored in 70% ethanol. Prey remains consisted principally Alessandri et al., 2001; Meissner et al., 2012). But there is a scar- of beaks of cephalopods (lower beaks were used for species city of knowledge in the eastern basin, where the only existing identification), otoliths and dentaries of bony fish (e.g. study is that of O¨ ztu¨rket al. (2007), who examined cephalopod Supplementary Figure S1 – Dentaries of Sudis hyalina) and remains in the stomachs of three by-caught striped dolphins. crustaceans, which were identified using reference materials Although cetaceans have been under legal protection in and published guides (Clarke, 1962, 1986; Mangold & Turkey since 1983, they still face the threat of being by-caught Fioroni, 1966; Schmidt, 1968; Wolff, 1984; Kocatas¸ et al., 1991; Lu & Ickeringill, 2002; Campana, 2004; Tuset et al., Corresponding author: 2008; Agiadi et al., 2010). It was assumed that the number A. Dede of prey fish was equal to half the number of the otoliths. For Email: [email protected] the beaks of cephalopods, lower rostral length (LRL) was 869 Downloaded from https://www.cambridge.org/core. University of Athens, on 28 Sep 2021 at 01:49:53, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0025315415001538 870 ayhan dede et al. Table 2. Food items found in six striped dolphin stomachs from the eastern Mediterranean Sea. Species Numbers Occurrence N%O% Osteichthyes Gadidae 9 0.51 5 83.3 Gonostomatidae 28 1.58 3 50.0 Moridae 1 0.06 1 16.7 Myctophidae 49 2.76 6 100 Diaphus spp. 690 38.83 6 100 Notoscopelus spp. 1 0.06 1 16.7 Notoscopelus elongatus 2 0.11 1 16.7 Ceratoscopelus maderensis 292 16.43 4 66.7 Myctophum punctatum 48 2.70 5 83.3 Electrona risso 20 1.13 4 66.7 Lampanyctus crocodilus 97 5.46 3 50.0 Stomiidae Chauliodus sloani 145 8.16 6 100 Fig. 1. Sampling areas in the eastern Mediterranean Sea. Numbers indicate the Paralepididae specimens listed in Table 1. Sudis hyalina 8 0.45 3 50.0 Phycidae 3 0.17 1 16.7 Sternoptychidae 1 0.06 1 16.7 Table 1. Details of the by-caught striped dolphins. Group totals (bony fishes) 1394 Cephalopoda No Sampling Date Depth Sex Length ∗ Ancistrocheiridae area no (m) (cm) Ancistrocheirus lesueurii 3 0.17 2 33.3 F1 1 29 June 2003 2000 Male 198 Brachioteuthidae F2 2 30 June 2003 2500 Female 166 Brachioteuthis riisei 16 0.90 2 33.3 F3 2 30 June 2003 2500 Male 198 Chiroteuthidae F4 2 30 June 2003 2500 Male 198 Chiroteuthis veranii 10 0.56 5 83.3 F5 2 30 June 2003 2500 Male 200 Chtenopterygidae F6 3 21 June 2004 1000 Male 124 Chtenopteryx sicula 7 0.39 3 50.0 Enoploteuthidae ∗ Number indicated in Figure 1. Abralia veranyi 56 3.15 4 66.7 Histioteuthidae Histioteuthis bonnellii 20 1.13 4 66.7 measured and estimated mantle length (ML) was calculated as Octopoteuthidae defined by Wolff (1984), Clarke (1986), Lu & Ickeringill Octopoteuthis sicula 5 0.28 3 50.0 (2002) and O¨ ztu¨rk et al. (2007). Onychoteuthidae Onychoteuthis banksii 110 6.19 6 100 Ancistroteuthis lichtensteini 5 0.28 1 16.7 Pyroteuthidae RESULTS Pyroteuthis margaritifera 12 0.68 3 50.0 Pterygioteuthis giardi 7 0.39 2 33.3 The occurrence of cephalopods, crustaceans and fish found in Sepiolidae six striped dolphin stomachs are presented in Table 2. In total, Heteroteuthis dispar 38 2.14 5 83.3 29 taxa were identified to species or family level and 1777 indi- Group totals (cephalopods) 289 vidual food items were counted. Crustacea Decapoda 53 2.98 1 16.7 Caridea 41 2.31 5 83.3 Bony fish Group totals (crustaceans) 94 Totals 1777 100 A total of 1394 bony fish belonging to eight families and nine species were identified in six stomachs. The major family was N, total number of each prey in the stomachs; O, number of stomachs in Myctophidae (lantern fish), representing 86.01% of the total which the prey species was found. number of fishes and 67.48% of the total number of all organ- isms. Diaphus spp. and Ceratoscopelus maderensis were the most predominant fishes, comprising 70.45% of the total Although a great majority of its stomach contents included number of fishes (Figure 2A), and 55.26% of total preys luminous deep-sea fish (Myctophidae, Gonostomatidae etc.) (Table 2). But only Diaphus spp. and Chauliodus sloani in the eastern Mediterranean (98.5%), epipelagic species were found in all stomachs, representing 59.90% of the total were not found in the stomach contents (Table 2). number of the fishes (Figure 2A), and 46.99% of the total prey (Table 2). Myctophum punctatum, Notoscopelus elongatus, Cephalopods Electrona risso, Sudis hyalina, Moridae sp., Phycidae sp. and Sternoptychidae sp. were reported for the first time in the In six stomachs 289 cephalopod lower beaks were present. stomach contents of striped dolphins in the Mediterranean Sea. Twelve species belonging to 10 families were identified. The Downloaded from https://www.cambridge.org/core. University of Athens, on 28 Sep 2021 at 01:49:53, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0025315415001538 stomach contents of striped dolphins 871 Fig. 2. Proportions of species found in the stomachs: (A) bony fishes; (B) cephalopods. species found in the stomach were pelagic and mesopelagic understand the feeding ecology of striped dolphins in the luminous cephalopods. As the only cephalopod species study area, although by-caught dolphins in the same location spotted in all stomach content analyses, Onychoteuthis may not be good enough representatives of the eastern banksii represented 38.06% of the total number of cephalo- Mediterranean population.