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NOAA Elasmobranch Bycatch Associated with the Shrimp Trawl Fishery Off the Pacific Coast of Costa Rica, Central America

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NOAA Elasmobranch Bycatch Associated with the Shrimp Trawl Fishery Off the Pacific Coast of Costa Rica, Central America 1 NOAA First U.S. Commissioner National Marine Fishery Bulletin established 1881 of Fisheries and founder Fisheries Service of Fishery Bulletin Abstract—Demersal sharks and rays Elasmobranch bycatch associated with the are common yet vulnerable compo- nents of the bycatch in tropical bot- shrimp trawl fishery off the Pacific coast of tom-trawl fisheries. Little is known about the elasmobranch assemblages Costa Rica, Central America associated with most of these fisher- ies, particularly within the eastern Tayler M. Clarke1,2 tropical Pacific. This study charac- Mario Espinoza2,3 terized the elasmobranch assem- blage associated with the shrimp Robert Ahrens4 trawl fishery along the Pacific coast Ingo S. Wehrtmann2,3 of Costa Rica. Between August 2008 and August 2012, 346 trawl hauls Email for contact author: [email protected] were conducted at depths of 18–350 m. These hauls resulted in a sample 1 Programa Gestión Integrada de Áreas Costeras Tropicales (GIACT) of 4564 elasmobranchs from 25 spe- Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) cies and 13 families. The Panam- Universidad de Costa Rica ic stingray (Urotrygon aspidura), 11501-2060 San José, Costa Rica rasptail skate (Raja velezi), brown smoothhound (Mustelus henlei), and 2 Unidad de Investigación Pesquera y Acuicultura (UNIP) witch guitarfish (Zapteryx xyster) ac- CIMAR counted for more than 66% of the Universidad de Costa Rica elasmobranch abundance within the 11501-2060 San José, Costa Rica bycatch. Depth was the main factor 3 Escuela de Biología influencing the elasmobranch assem- Universidad de Costa Rica blage; species richness was signifi- 11501-2060 San José, Costa Rica cantly higher at depths <100 m than 4 Fisheries and Aquatic Sciences at other depths. Two groups of elas- School of Forest Resources and Conservation mobranchs were identified: the first University of Florida was found in shallow waters (<50 P.O. Box 110410 m), and the second was observed Gainesville, Florida 32653 at depths of 50–350 m. Sex and size segregation patterns are also influenced by depth. Moreover, we documented the shift of the bottom- Overfishing and habitat degradation diversity of elasmobranch species trawl fishery toward shallow-water have caused significant declines in and data-deficient fisheries (Barker resources—a change that could be elasmobranch abundance (Dulvy et and Schluessel, 2005; Cheung et al., problematic considering that elasmo- al., 2008; Ferretti et al., 2008; Dulvy 2005; White and Sommerville, 2010). branch diversity is higher in shallow Several studies conducted in the waters. et al., 2014). Most of the global elas- mobranch catch is incidental and tropics have reported large declines originates from fisheries that target in the abundance of demersal elas- higher-valued teleosts or crustaceans mobranchs associated with bottom- (Stevens et al., 2000; Walker, 2005; trawl fisheries (e.g., Thailand: Ste- Wehrtmann et al., 2012; Worm et vens et al., 2000; Australia: Graham al., 2013). In general, elasmobranch et al., 2001; Gulf of Mexico: Shepherd bycatch is not regulated or even re- and Myers, 2005). Nevertheless, elas- ported, especially in developing coun- mobranch bycatch has been poorly tries (Barker and Schluessel, 2005; studied in many tropical regions, in- Manuscript submitted 26 August 2014. Cheung et al., 2005; Walker, 2005). cluding the Eastern Tropical Pacific Manuscript accepted 10 September 2015. Furthermore, sharks and rays tend (ETP; from Mexico to Peru), where Fish. Bull. 114:1–17 (2016). to exhibit slow growth rates, late ma- abundance trends remain unclear Online publication date: 22 October 2015. turity, and low fecundity, and, there- (Mejía-Falla and Navia1; López-Mar- doi: 10.7755/FB.114.1 fore, they have a low resilience to in- 1 Mejía-Falla, P. A., and A. F. Navia (eds.). The views and opinions expressed or tense fishing pressures (Cortés, 2000; Dulvy and Reynolds, 2002; Frisk et 2011. Estadísticas pesqueras de tibu- implied in this article are those of the rones y rayas en el Pacífico Colombiano. author (or authors) and do not necessarily al., 2005). The severity of this issue Documento técnico Fundación SQUA- reflect the position of the National increases in the tropics as a result LUS No. FS0111, 70 p. [Available at Marine Fisheries Service, NOAA. of the interaction between a high website.] 2 Fishery Bulletin 114(1) tínez et al., 2010; Clarke et al., 2014). The best infor- patterns in relation to geographic position, depth, year, mation available is obtained from the Pacific coast of season, and diel period; 2) the relationship between Colombia, where significant changes in elasmobranch depth and number of elasmobranch species; 3) sex and species composition and abundance have been detected size segregation patterns of the most common elasmo- since the 1990s (Mejía-Falla and Navia1). Other coun- branch species; 4) the effects of latitude, depth, season, tries, such as Mexico (López-Martínez et al., 2010), year, and sampling type on elasmobranch species com- have basic information that is limited to species lists position; and 5) and a comparison of our results of spe- and short-term relative abundance. In the remaining cies composition with those from historical data. This countries of the ETP, even this basic information is not baseline information on the demersal elasmobranch available. Scarcity of published data has hindered at- assemblage of Costa Rica will enable an examination tempts to estimate the effect of shrimp trawl fisheries of the effects of management strategies to be imple- on the elasmobranch assemblage in the ETP (Espinoza mented in the near future. et al., 2012; Espinoza et al., 2013; Clarke et al., 2014). The commercial shrimp trawl fishery of Costa Rica operates exclusively along the Pacific coast, in shallow- Materials and methods water and deepwater areas (Wehrtmann and Nielsen- Muñoz, 2009). The shallow-water (<100 m) fishery Study area began in the 1950s, but the rapid depletion of coastal resources forced the fleet to expand their oprations The Pacific coastline of Costa Rica is highly irregular toward deeper waters by the 1980s (Wehrtmann and and is approximately 1254 km long, borders 3 large Nielsen-Muñoz, 2009). The shrimp trawl fishery in Cos- gulfs and a continental shelf that together cover an ta Rica has elevated bycatch rates of up to 93% of the area of 15,600 km2 (Fig. 1; Wehrtmann and Cortés, total biomass catch (Wehrtmann and Nielsen-Muñoz, 2009). Costa Rica has pronounced rainy (May–Novem- 2009; Arana et al., 2013). Moreover, the results of a ber) and dry (December–April) seasons (Fiedler and long-term (2004–2012) fishery-independent monitoring Talley, 2006). Although temperature remains relatively program indicate that a shift has occurred in the over- constant across seasons (27–30°C), coastal productivity all structure of the demersal community of Costa Rica along most of the central and southern Pacific coast (Wehrtmann and Nielsen–Muñoz, 2009; Hernáez et al., increases during the rainy season as a consequence of 2011; Wehrtmann et al., 2012; Espinoza et al., 2012, nutrient input from the largest rivers in this country: 2013). Changes in elasmobranch abundance associated the Tempisque, Tárcoles, and Térraba rivers (Fiedler with this shift remain poorly understood, given that and Talley, 2006; Wehrtmann and Cortés, 2009). this monitoring program was designed to study deep- The northern Pacific coast is characterized by strong, water shrimp resources and the crustacean bycatch as- seasonal upwelling between December and February sociated with the fisheries that target them. and by a limited freshwater input resulting from the Together, the lack of biological information and absence of large rivers (Jiménez, 2001; Fiedler, 2002). the unreliability or nonexistence of landing statistics The coast of the central Pacific region is influenced by have limited the development of sustainable manage- 2 large estuarine systems, the Golfo de Nicoya and the ment practices and conservation strategies for elasmo- Térraba-Sierpe delta; both estuaries have large man- branchs in Costa Rica. Given the fishery’s current man- grove forests in close proximity to coral communities agement framework is poorly enforced, the sustainabil- or rocky reefs (Quesada-Alpízar and Cortés, 2006). ity and environmental impacts have become a serious The southern Pacific coast has a very steep continen- concern. Concern regarding the effect of this fishery tal slope and includes the Golfo Dulce tropical fjord culminated in a constitutional judgment (Sentence No. (Quesada-Alpízar and Cortés, 2006). 2013-10540), enacted by the government of Costa Rica and that prohibited the Costa Rican Institute of Fish- Sampling eries and Aquaculture (INCOPESCA) from granting or renewing commercial shrimp trawl licenses. All current Sampling effort was concentrated near the main fishing licenses for this fishery are set to expire in 2018, and port, Puntarenas, located in the northern Pacific region an ongoing national decision process will eventually (Fig.1). Data for this study were collected from 3 types define the legal framework requirements for any sus- of surveys: 1) deepwater, 2) monitoring, and 3) com- tainable shrimp trawling in Costa Rica. mercial (Fig. 1). Sampling depth range was divided into According to the Code of Conduct for Responsible shallow (<50 m), intermediate (50–100 m).and deep Fisheries, the effects of a fishery on an ecosystem (>100 m). Bottom trawls were carried out exclusively on should be accounted
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