DOCSLIB.ORG

Population Structure of the Thornback Ray (Raja Clavata L.) in British Waters ⁎ Malia Chevolot A, , Jim R

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Population Structure of the Thornback Ray (Raja Clavata L.) in British Waters ⁎ Malia Chevolot A, , Jim R Journal of Sea Research 56 (2006) 305–316 www.elsevier.com/locate/seares Population structure of the thornback ray (Raja clavata L.) in British waters ⁎ Malia Chevolot a, , Jim R. Ellis b, Galice Hoarau a, Adriaan D. Rijnsdorp c, Wytze T. Stam a, Jeanine L. Olsen a a Department of Marine Benthic Ecology and Evolution, Center for Ecological and Evolutionary Studies, University of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands b Centre for Environment Fisheries and Aquaculture Sciences (CEFAS), Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK c Wageningen Institute for Marine Resources and Ecological Studies (IMARES), Animal Sciences Group, Wageningen UR, P.O. Box 68, 1970 AB IJmuiden, The Netherlands Received 27 July 2005; accepted 24 May 2006 Available online 17 June 2006 Abstract Prior to the 1950s, thornback ray (Raja clavata L.) was common and widely distributed in the seas of Northwest Europe. Since then, it has decreased in abundance and geographic range due to over-fishing. The sustainability of ray populations is of concern to fisheries management because their slow growth rate, late maturity and low fecundity make them susceptible to exploitation as victims of by-catch. We investigated the population genetic structure of thornback rays from 14 locations in the southern North Sea, English Channel and Irish Sea. Adults comprised <4% of the total sampling despite heavy sampling effort over 47 hauls; thus our results apply mainly to sexually immature individuals. Using five microsatellite loci, weak but significant population differentiation was detected with a global FST = 0.013 (P < 0.001). Pairwise Fst was significant for 75 out of 171 comparisons. Although earlier tagging studies suggest restricted foraging distances from home areas, the absence of genetic differentiation between some distant populations suggests that a substantial fraction of individuals migrate over wide areas. Autumn/winter locations appear to have a lower level of differentiation than spring/summer, which could be due to seasonal migration. Management and conservation of thornback ray populations will be challenging as population structure appears to be dynamic in space and time. © 2006 Elsevier B.V. All rights reserved. Keywords: Elasmobranchs; Genetic structure; Microsatellite; Thornback ray; Rajidae 1. Introduction Africa (Stehmann and Bürkel, 1994), though their taxonomic status in these waters is unclear. Around Thornback ray, Raja clavata, is a widely distributed the British Isles, thornback rays are most abundant in skate (Rajiformes: Rajidae) in the eastern Atlantic, coastal waters and large bays, including The Wash, ranging from Norway and Iceland to Northwest Africa, Outer Thames Estuary, Solent, Carmarthen Bay, Cardi- including the Mediterranean and Black Seas. They may gan Bay, Liverpool Bay and Solway Firth (Ellis et al., also occur in the Atlantic and Indian Oceans of southern 2005). Prior to the 1950s, thornback rays were common and widespread in the North Sea, but have declined ⁎ Corresponding author. thereafter in distribution and abundance (Walker and E-mail address: [email protected] (M. Chevolot). Heessen, 1996; Walker and Hislop, 1998). 1385-1101/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.seares.2006.05.005 306 M. Chevolot et al. / Journal of Sea Research 56 (2006) 305–316 Thornback rays are targeted in inshore longline and be rare, as well as between the English and French coasts gillnet fisheries in coastal waters of the British Isles, and across the English Channel. It was hypothesised that this are also an important component of the mixed demersal separation was probably due to the deeper waters and trawl fisheries. Despite R. clavata being one of the most strong currents in the Dover Strait (Walker et al., 1997). commercially valuable rays, the economic value of their Taken together, tagging studies suggest that R. clavata total catch is small in comparison to other demersal may have restricted ranges and potentially strong species (e.g. sole and plaice) and as such they have not localised population differentiation-particularly among been the focus of fisheries management. Between 1956 younger individuals. and 1995, R. clavata disappeared from the waters along To date, only a few population genetic studies based on the continental coasts of the North Sea and showed an nuclear markers have been conducted on elasmobranchs, overall decline of nearly 80% in this area (Walker and and all of these have been on sharks. Heist and Gold Heessen, 1996). Similarly, they are thought to have (1999) found no differentiation (three microsatellite loci) declined by approximately 45% between 1988 and 1997 in population structure of sandbar sharks (Carcharinus in the Irish Sea (Dulvy et al., 2000). This rapid decrease plumbeus) between the mid-Atlantic Bight and the has led to concern about the sustainability of ray western Gulf of Mexico. Schrey and Heist (2003) populations (Walker et al., 1997; Dulvy et al., 2000), observed evidence of population differentiation (four especially given their low fecundity, slow growth, and microsatellite loci) in shortfin mako shark (Isurus late maturity, which makes them potentially vulnerable oxyrinchus) between the North Atlantic and North Pacific. to exploitation (Brander, 1981; Heist, 1999). Feldheim et al. (2001) found weak but significant The fecundity of R. clavata is thought to be in the population structure (four microsatellite loci) in the range of 48–150 eggs per year (Holden, 1975; Ryland lemon shark (Negaprion brevirostris) in the western and Ajayi, 1984; Ellis and Shackley, 1995). Following Atlantic Ocean. Keeney et al. (2005) also found a weak mating in early spring, eggs are deposited regularly, with but significant population structure (8 microsatellite loci the spawning season occurring between February and and control region of the mtDNA) in the blacktip shark September (Holden, 1975), though the egg-laying (Carcharinus limbatus) between nine nursery areas periods of individuals may be more restricted (Holden (Northwestern Atlantic, Eastern, Western Gulf of Mexico, et al., 1971; Ellis and Shackley, 1995). Fertilised eggs North Yucatan and Belize). In studies where nuclear and are deposited as egg cases on the seabed and, after 4– mitochondrial markers were used, evidence for male- 5 months incubation, fully formed rays (ca. 8 cm disc biased dispersal and female philopatry has been suggested width) hatch (Ellis and Shackley, 1995). Tagging studies for white shark Carcharodon carcharias (Pardini et al., have shown that juveniles tend to remain in shallow 2001), shortfin mako (Schrey and Heist, 2003), lemon waters (10–30 m deep) for several years, with shark (Feldheim et al., 2001) and blacktip shark (Keeney recaptured individual close to the point of release et al., 2005). Only one population structure study has been (Walker et al., 1997). conducted on a Rajidae by Blake (1976) on thornback R. clavata matures at between 9 and 12 y of age rays in the Irish Sea using a eye-lens protein. No (Nottage and Perkins, 1983). At this stage, adults show differentiation was found, probably due to the lack of seasonal movements, from deeper waters (10 to 30 m) in polymorphism of the allozyme. winter, to shallower waters (<10 m) in spring, where they Here, we investigate the population genetic structure are presumed to mate and spawn (Walker et al., 1997). of R. clavata in the southern North Sea, English Despite these seasonal movements, past tagging experi- Channel, and Irish Sea using five microsatellite loci. ments indicated that 100% of the individuals remained The objectives were to determine the spatial scale of R. within a 60 nautical miles (nmi) area and 80% remained clavata population differentiation, assess the home within 20 nmi. This ‘home range’ has since been extended range based on assignment tests, and to compare to a maximum travelling distance of 70 nmi from studies migratory movements based on genetic data with using Data Storage Tags (DSTs) (Hunter et al., 2005b). those based on earlier tagging data. Their study also confirmed the seasonal movement pattern of thornback for mature and immature individuals 2. Material and methods (30–60 cm total length), and showed a philopatric behaviour as most individual rays were found in the 2.1. Sampling and DNA extraction same area during spring/summer time every year (Hunter et al., 2005a). Wider-ranging migrations between the A total of 483 immature rays were sampled from 14 southern North Sea and the English Channel appeared to locations during standard, annual bottom trawl surveys M. Chevolot et al. / Journal of Sea Research 56 (2006) 305–316 307 conducted by various fisheries institutes from 2002 to was determined using internal lane standard (GENES- 2004 (Table 1). Five out of the 14 locations were CAN™ 350 ROX™) and GENESCAN™ software. sampled at different time period (Fig. 1, Table 1). Adults were only rarely represented in the sampling (N = 20) 2.3. Data analysis and, therefore, not included in the population structure analysis. Individuals were classified as adult or The software package MICRO-CHECKER 2.2.1 (Van immature based on reproductive criteria, i.e., presence Oosterhout et al., 2004) was used to check for of fully differentiated shell glands for females and fully genotyping errors due to null alleles, stuttering, and developed testes and claspers for males (Stehmann, large allele drop-out for all loci and all locations. 1995). If reproductive data were not available, total Allelic diversity was calculated and corrected for length (<55 cm for immature) was substituted. sample size using GENCLONE β version (Arnaud-Haond Sampling was not easy as any single haul (fishing and Belkhir, available on request). In order to compare for 30 min at 4 nmi/h) provided only a small number of diversity among populations of different sample sizes, individuals (mean=4.7 individuals/haul, SD=5.8). the program performs a jacknife re-sampling of Single hauls producing >20 individuals occurred only individuals at each location.
Load more

Recommended publications
  • Sharks in Crisis: a Call to Action for the Mediterranean
    REPORT 2019 SHARKS IN CRISIS: A CALL TO ACTION FOR THE MEDITERRANEAN WWF Sharks in the Mediterranean 2019 | 1 fp SECTION 1 ACKNOWLEDGEMENTS Written and edited by WWF Mediterranean Marine Initiative / Evan Jeffries (www.swim2birds.co.uk), based on data contained in: Bartolí, A., Polti, S., Niedermüller, S.K. & García, R. 2018. Sharks in the Mediterranean: A review of the literature on the current state of scientific knowledge, conservation measures and management policies and instruments. Design by Catherine Perry (www.swim2birds.co.uk) Front cover photo: Blue shark (Prionace glauca) © Joost van Uffelen / WWF References and sources are available online at www.wwfmmi.org Published in July 2019 by WWF – World Wide Fund For Nature Any reproduction in full or in part must mention the title and credit the WWF Mediterranean Marine Initiative as the copyright owner. © Text 2019 WWF. All rights reserved. Our thanks go to the following people for their invaluable comments and contributions to this report: Fabrizio Serena, Monica Barone, Adi Barash (M.E.C.O.), Ioannis Giovos (iSea), Pamela Mason (SharkLab Malta), Ali Hood (Sharktrust), Matthieu Lapinksi (AILERONS association), Sandrine Polti, Alex Bartoli, Raul Garcia, Alessandro Buzzi, Giulia Prato, Jose Luis Garcia Varas, Ayse Oruc, Danijel Kanski, Antigoni Foutsi, Théa Jacob, Sofiane Mahjoub, Sarah Fagnani, Heike Zidowitz, Philipp Kanstinger, Andy Cornish and Marco Costantini. Special acknowledgements go to WWF-Spain for funding this report. KEY CONTACTS Giuseppe Di Carlo Director WWF Mediterranean Marine Initiative Email: [email protected] Simone Niedermueller Mediterranean Shark expert Email: [email protected] Stefania Campogianni Communications manager WWF Mediterranean Marine Initiative Email: [email protected] WWF is one of the world’s largest and most respected independent conservation organizations, with more than 5 million supporters and a global network active in over 100 countries.
    [Show full text]
  • Skates and Rays Diversity, Exploration and Conservation – Case-Study of the Thornback Ray, Raja Clavata
    UNIVERSIDADE DE LISBOA FACULDADE DE CIÊNCIAS DEPARTAMENTO DE BIOLOGIA ANIMAL SKATES AND RAYS DIVERSITY, EXPLORATION AND CONSERVATION – CASE-STUDY OF THE THORNBACK RAY, RAJA CLAVATA Bárbara Marques Serra Pereira Doutoramento em Ciências do Mar 2010 UNIVERSIDADE DE LISBOA FACULDADE DE CIÊNCIAS DEPARTAMENTO DE BIOLOGIA ANIMAL SKATES AND RAYS DIVERSITY, EXPLORATION AND CONSERVATION – CASE-STUDY OF THE THORNBACK RAY, RAJA CLAVATA Bárbara Marques Serra Pereira Tese orientada por Professor Auxiliar com Agregação Leonel Serrano Gordo e Investigadora Auxiliar Ivone Figueiredo Doutoramento em Ciências do Mar 2010 The research reported in this thesis was carried out at the Instituto de Investigação das Pescas e do Mar (IPIMAR - INRB), Unidade de Recursos Marinhos e Sustentabilidade. This research was funded by Fundação para a Ciência e a Tecnologia (FCT) through a PhD grant (SFRH/BD/23777/2005) and the research project EU Data Collection/DCR (PNAB). Skates and rays diversity, exploration and conservation | Table of Contents Table of Contents List of Figures ............................................................................................................................. i List of Tables ............................................................................................................................. v List of Abbreviations ............................................................................................................. viii Agradecimentos ........................................................................................................................
    [Show full text]
  • Spatial Ecology and Fisheries Interactions of Rajidae in the Uk
    UNIVERSITY OF SOUTHAMPTON FACULTY OF NATURAL AND ENVIRONMENTAL SCIENCES Ocean and Earth Sciences SPATIAL ECOLOGY AND FISHERIES INTERACTIONS OF RAJIDAE IN THE UK Samantha Jane Simpson Thesis for the degree of DOCTOR OF PHILOSOPHY APRIL 2018 UNIVERSITY OF SOUTHAMPTON 1 2 UNIVERSITY OF SOUTHAMPTON ABSTRACT FACULTY OF NATURAL AND ENVIRONMENTAL SCIENCES Ocean and Earth Sciences Doctor of Philosophy FINE-SCALE SPATIAL ECOLOGY AND FISHERIES INTERACTIONS OF RAJIDAE IN UK WATERS by Samantha Jane Simpson The spatial occurrence of a species is a fundamental part of its ecology, playing a role in shaping the evolution of its life history, driving population level processes and species interactions. Within this spatial occurrence, species may show a tendency to occupy areas with particular abiotic or biotic factors, known as a habitat association. In addition some species have the capacity to select preferred habitat at a particular time and, when species are sympatric, resource partitioning can allow their coexistence and reduce competition among them. The Rajidae (skate) are cryptic benthic mesopredators, which bury in the sediment for extended periods of time with some species inhabiting turbid coastal waters in higher latitudes. Consequently, identifying skate fine-scale spatial ecology is challenging and has lacked detailed study, despite them being commercially important species in the UK, as well as being at risk of population decline due to overfishing. This research aimed to examine the fine-scale spatial occurrence, habitat selection and resource partitioning among the four skates across a coastal area off Plymouth, UK, in the western English Channel. In addition, I investigated the interaction of Rajidae with commercial fisheries to determine if interactions between species were different and whether existing management measures are effective.
    [Show full text]
  • Review of Migratory Chondrichthyan Fishes
    Convention on the Conservation of Migratory Species of Wild Animals Secretariat provided by the United Nations Environment Programme 14 TH MEETING OF THE CMS SCIENTIFIC COUNCIL Bonn, Germany, 14-17 March 2007 CMS/ScC14/Doc.14 Agenda item 4 and 6 REVIEW OF MIGRATORY CHONDRICHTHYAN FISHES (Prepared by the Shark Specialist Group of the IUCN Species Survival Commission on behalf of the CMS Secretariat and Defra (UK)) For reasons of economy, documents are printed in a limited number, and will not be distributed at the meeting. Delegates are kindly requested to bring their copy to the meeting and not to request additional copies. REVIEW OF MIGRATORY CHONDRICHTHYAN FISHES IUCN Species Survival Commission’s Shark Specialist Group March 2007 Taxonomic Review Migratory Chondrichthyan Fishes Contents Acknowledgements.........................................................................................................................iii 1 Introduction ............................................................................................................................... 1 1.1 Background ...................................................................................................................... 1 1.2 Objectives......................................................................................................................... 1 2 Methods, definitions and datasets ............................................................................................. 2 2.1 Methodology....................................................................................................................
    [Show full text]
  • A Review of Longnose Skates Zearaja Chilensisand Dipturus Trachyderma (Rajiformes: Rajidae)
    Univ. Sci. 2015, Vol. 20 (3): 321-359 doi: 10.11144/Javeriana.SC20-3.arol Freely available on line REVIEW ARTICLE A review of longnose skates Zearaja chilensis and Dipturus trachyderma (Rajiformes: Rajidae) Carolina Vargas-Caro1 , Carlos Bustamante1, Julio Lamilla2 , Michael B. Bennett1 Abstract Longnose skates may have a high intrinsic vulnerability among fishes due to their large body size, slow growth rates and relatively low fecundity, and their exploitation as fisheries target-species places their populations under considerable pressure. These skates are found circumglobally in subtropical and temperate coastal waters. Although longnose skates have been recorded for over 150 years in South America, the ability to assess the status of these species is still compromised by critical knowledge gaps. Based on a review of 185 publications, a comparative synthesis of the biology and ecology was conducted on two commercially important elasmobranchs in South American waters, the yellownose skate Zearaja chilensis and the roughskin skate Dipturus trachyderma; in order to examine and compare their taxonomy, distribution, fisheries, feeding habitats, reproduction, growth and longevity. There has been a marked increase in the number of published studies for both species since 2000, and especially after 2005, although some research topics remain poorly understood. Considering the external morphological similarities of longnose skates, especially when juvenile, and the potential niche overlap in both, depth and latitude it is recommended that reproductive seasonality, connectivity and population structure be assessed to ensure their long-term sustainability. Keywords: conservation biology; fishery; roughskin skate; South America; yellownose skate Introduction Edited by Juan Carlos Salcedo-Reyes & Andrés Felipe Navia Global threats to sharks, skates and rays have been 1.
    [Show full text]
  • Modelling Abundance Hotspots for Data-Poor Irish Sea Rays
    Modelling abundance hotspots for data-poor Irish Sea rays Simon Dedmana,b, Rick Officera, Deirdre Brophya, Maurice Clarkeb, David G. Reidb a Marine and Freshwater Research Centre, Galway-Mayo Institute of Technology, Galway, Ireland, b Marine Institute, Rinville, Oranmore, Co. Galway, Ireland Emails: [email protected] , [email protected] , [email protected] , [email protected] , [email protected] Abstract Skates and rays represent one of the most vulnerable components of fish communities in temperate demersal fisheries such as the Irish Sea. They also tend to be data poor in comparison to commercially exploited teleost fish. Spatial management has been suggested as an important tool to protect these species, but requires an understanding of the abundance distribution, and the relationship the abundance distribution has with the environment at both adult and juvenile life history stages. Here we modelled bottom trawl survey data using delta log-normal boosted regression trees on to derive rays’ spatial abundance, and environmental links. The modelling approach allowed the development of high resolution predictive maps of abundance of four skate and ray species targeted by fishing activity: thornback, spotted, cuckoo and blonde rays. The distributions of these species were driven by a general preference for sand and coarser substrates as well as higher salinities, temperatures and currents speeds. Spatial comparisons between abundance distributions and locations of skate and ray commercial landings indicated that the main hotspots for the investigated species are outside of the main commercial fishing areas and overlap with potential MPAs proposed for wider ecosystem protection. The method offers a useful tool for selecting potential MPA’s to assist the management and conservation of data-poor species.
    [Show full text]
  • Oceanological and Hydrobiological Studies
    Oceanological and Hydrobiological Studies International Journal of Oceanography and Hydrobiology Volume 50, No. 2, June 2021 pages (115-127) ISSN 1730-413X eISSN 1897-3191 Biology of the thornback ray (Raja clavata Linnaeus, 1758) in the North Aegean Sea by Abstract 1, The study deals with aspects of the population Koray Cabbar *, dynamics in the thornback ray (Raja clavata L., 1758), one 2 Cahide Çiğdem Yiğin of the most abundant cartilaginous fish caught in the North Aegean Sea. Females accounted for 73.08% and males 26.92% of all individuals. Total length of females and males ranged between 50.2 and 89.9 cm (disc width: 33.4–62.0 cm), and between 43.1 cm and 82.7 cm (disc width: 30.7–64.2 cm), respectively. Relationships between total length (TL) and total weight (TW), and between DOI: 10.2478/oandhs-2021-0011 disc width (DW) and total weight (TW) were described by 3.10 3.03 Category: Original research paper the equations: TW = 0.0041 TL and TW = 0.0178 DW , respectively. Age data derived from vertebrae readings Received: September 23, 2020 were used to estimate growth parameters using the von Accepted: December 1, 2020 −1 Bertalanffy function: L∞ = 101.71 cm, K = 0.18 y , t0 = −0.07 −1 y for males and L∞ = 106.54 cm, K = 0.16 y , t0 = −0.28 y for females. The maximum age was 8 years for males 1Çanakkale Onsekiz Mart University, and females. Total length at first maturity of males and females was 70.9 cm and 81.2 cm, respectively.
    [Show full text]
  • The Conservation Status of North American, Central American, and Caribbean Chondrichthyans the Conservation Status Of
    The Conservation Status of North American, Central American, and Caribbean Chondrichthyans The Conservation Status of Edited by The Conservation Status of North American, Central and Caribbean Chondrichthyans North American, Central American, Peter M. Kyne, John K. Carlson, David A. Ebert, Sonja V. Fordham, Joseph J. Bizzarro, Rachel T. Graham, David W. Kulka, Emily E. Tewes, Lucy R. Harrison and Nicholas K. Dulvy L.R. Harrison and N.K. Dulvy E.E. Tewes, Kulka, D.W. Graham, R.T. Bizzarro, J.J. Fordham, Ebert, S.V. Carlson, D.A. J.K. Kyne, P.M. Edited by and Caribbean Chondrichthyans Executive Summary This report from the IUCN Shark Specialist Group includes the first compilation of conservation status assessments for the 282 chondrichthyan species (sharks, rays, and chimaeras) recorded from North American, Central American, and Caribbean waters. The status and needs of those species assessed against the IUCN Red List of Threatened Species criteria as threatened (Critically Endangered, Endangered, and Vulnerable) are highlighted. An overview of regional issues and a discussion of current and future management measures are also presented. A primary aim of the report is to inform the development of chondrichthyan research, conservation, and management priorities for the North American, Central American, and Caribbean region. Results show that 13.5% of chondrichthyans occurring in the region qualify for one of the three threatened categories. These species face an extremely high risk of extinction in the wild (Critically Endangered; 1.4%), a very high risk of extinction in the wild (Endangered; 1.8%), or a high risk of extinction in the wild (Vulnerable; 10.3%).
    [Show full text]
  • Aquatic Zoos
    AQUATIC ZOOS A critical study of UK public aquaria in the year 2004 by Jordi Casamitjana CONTENTS INTRODUCTION ---------------------------------------------------------------------------------------------4 METHODS ------------------------------------------------------------------------------------------------------7 Definition ----------------------------------------------------------------------------------------------7 Sampling and public aquarium visits --------------------------------------------------------------7 Analysis of the data --------------------------------------------------------------------------------10 UK PUBLIC AQUARIA PROFILE ------------------------------------------------------------------------11 Types of public aquaria ----------------------------------------------------------------------------11 Animals kept in UK public aquaria----------------------------------------------------------------12 Number of exhibits in UK pubic aquaria --------------------------------------------------------18 Biomes of taxa kept in UK public aquaria ------------------------------------------------------19 Exotic versus local taxa kept in UK public aquaria --------------------------------------------20 Trend in the taxa kept in UK public aquaria over the years ---------------------------------21 ANIMAL WELFARE IN UK PUBLIC AQUARIA ------------------------------------------------------23 ABNORMAL BEHAVIOUR --------------------------------------------------------------------------23 Occurrence of stereotypy in UK public aquaria --------------------------------------29
    [Show full text]
  • Fishery of Sinop Coasts in the Black Sea Surveys
    RESEARCH ARTICLE Eur J Biol 2018; 77(1): 18-25 Fishery of Sinop Coasts in the Black Sea Surveys Levent Bat1*, Fatih Sahin1, Murat Sezgin1, Sedat Gonener2, Ercan Erdem3, Ugur Ozsandikci2 1Sinop University, Fisheries Faculty, Department of Hydrobiology, Sinop, Turkey 2Sinop University, Fisheries Faculty, Department of Fishing Technology and Processing, Sinop, Turkey 3General Directorate of Fisheries and Aquaculture, Ministry of Food Agriculture and Livestock, Ankara, Turkey Please cite this article as: Bat L, Sahin F, Sezgin M, Gonener S, Erdem E, Ozsandikci U. Fishery of Sinop Coasts in the Black Sea Surveys. Eur J Biol 2018; 77(1): 18-25. ABSTRACT Objective: The current work was carried out between 2013-2014 during the fishing periods to evaluate certain fish aggloremations within 3 miles of the coastal zone. Therefore, some basic characteristics of fish populations along the Inceburun coast of the Sinop province of the Black Sea were examined. Materials and Methods: Data was collected from 5 trawl operations in the Sinop-Inceburun Region of the Black Sea at depths of 20 to 39 meters at 5 different locations. Biometric measurements of each species was made. A literature search was performed to gather information about the status of threatened fish species found in the region. The length-weight parameters of 4 commercial fish species were estimated. Results: During the fishing season between 1st September 2013 and 15th April 2014 different fish species were captured depending on the season and climate. In these surveys, 16 teleost species from 15 families, 2 elasmobranch species from 2 families and 2 species of invertebrates were recorded from 5 different stations.
    [Show full text]
  • Reproductive Biology of Raja Clavata (Elasmobranchii: Rajidae) from Southern Black Sea Coast Around Turkey
    Helgol Mar Res (2012) 66:117–126 DOI 10.1007/s10152-011-0252-5 ORIGINAL ARTICLE Reproductive biology of Raja clavata (Elasmobranchii: Rajidae) from Southern Black Sea coast around Turkey Hacer Saglam • Orhan Ak Received: 6 September 2010 / Revised: 17 February 2011 / Accepted: 8 March 2011 / Published online: 22 March 2011 Ó Springer-Verlag and AWI 2011 Abstract Specimens of Raja clavata were monthly col- can be classified as equilibrium (K-selected) strategists and lected at the coast of Havaalanı (Trabzon/Turkey) from typically share the biological characteristics of low January 2009 to December 2009 at depths between 20 and fecundity, late maturity, high juvenile survivorship, slow 40 m. A total of 230 individuals of thornback ray (131 body growth, and long life span (Hoenig and Gruber 1990; females and 99 males) were collected by bottom trawls Winemiller and Rose 1992; Camhi et al. 1998). Equilib- during research cruises. Using logistic regression, it was rium strategists tend to have slow rates of population determined that TL at 50% maturity of males was 718 mm growth and generally cannot sustain high levels of fishing TL and of females 746 mm TL. The ovarian fecundity pressure (Holden 1974; Hoenig and Gruber 1990). ranged from 27 to 60 yellow follicles in both ovaries. Thornback rays, Raja clavata, are found in coastal Females carrying egg cases were found in July and Octo- waters of the northeast Atlantic and the Mediterranean and ber. Variations in the gonadosomatic and hepatosomatic Black Seas (Stehmann and Bu¨rkel 1984). Thornback ray is indices indicated a continuous reproductive cycle during a bottom-dwelling species on the shelf and upper slope the year.
    [Show full text]
  • Thornback Ray Family Rajidae Max Age: 15 Years
    Raja clavata Max size: 100 cm Thornback Ray Family Rajidae Max age: 15 years Introduction Taxonomy: The thornback ray (or roker) Raja clavata, Linnaeus, 1758 (Order: Rajiformes, Family: Rajidae) is one of about 13 species of skate that are known from the North Sea and adjacent waters. Comm. common names Danish Sømrokke Icelandic Dröfnuskata Dutch Stekelrog Latvian Dzelkņraja English Roker / Thornback ray Norwegian Piggskate Estonian Astelrai Polish Raja nabijana a. ciernista Faeroese Naglaskøta Portuguese Raia lenga / Raia brocheada Finnish Okarausku Russian Колючий скат French Raie bouclée Spanish Raya de clavos German Nagelroche Swedish Knaggrocka General: Thornback ray is one of the more common and widespread skates in the NE Atlantic and Mediterranean and is also one of the dominant species in commercial landings. Minimum Landing Size: Although there is no EU regulation, individuals <40 cm length tend to be discarded. Regional Sea Fisheries Committees in England and Wales have the option of establishing by-laws for the fisheries operating in the inshore waters (extending to 6nm from shore). Within the North Sea area, the Kent and Essex Sea Fisheries Committee has established a minimum size of 40 cm disc width for skates and rays (disc width being used because the tails are often cut before landing). Distribution Biogeographical distribution: Thornback ray occurs in coastal waters of the North-East Atlantic from the Faeroe Islands, Iceland and Norway in the north to northwestern Africa, including the Skagerrak, Kattegat and western Baltic Sea, and the Mediterranean and Black Seas [1]. It also occurs off western Africa, including South Africa and, more recently, has been found in the Southwestern Indian Ocean [2].
    [Show full text]