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(Tteds) for Bycatch Reduction in Suriname's Seabob Shrimp Trawl Fishery

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(Tteds) for Bycatch Reduction in Suriname's Seabob Shrimp Trawl Fishery Sustainable Management of Bycatch in Latin America and Caribbean Trawl Fisheries REBYC-II LAC - SURINAME Evaluating Trash-and-Turtle Excluder Devices (TTEDs) for bycatch reduction in Suriname’s seabob shrimp trawl fishery - December 2017 - By Pieter Meeremans1, Tomas Willems2 and Yolanda Babb-Echteld3 1Technical Project Assistant REBYC-II LAC 2National Project Coordinator REBYC-II LAC 3Act. Director of Fisheries Ministry of Agriculture, Animal Husbandry and Fisheries (LVV), Fisheries Department Cornelis Jongbawstraat 50, Paramaribo, Suriname Contact: [email protected] 1 1. Introduction Atlantic seabob shrimp (Xiphopenaeus kroyeri) is a relatively small species of penaeid shrimp with a short life span, living in shallow coastal waters on a high mud content bottom (e.g. Freire et al., 2011). The species has a wide geographical range, occurring along the Central Western Atlantic coast from Sao Paulo (Brazil) in the south up to Florida (USA) in the north. In Suriname, seabob is traditionally caught with fyke nets in estuaries (Babb-Echteld, 2008). Since 1996, industrial trawl fisheries started targeting seabob as well (Chin-A-Lin and IJspol, 2000; LVV Fisheries Department, 2013). Industrial seabob fisheries use ‘Florida-type’ demersal outrigger trawlers, equipped with paired trawls in ‘quad rig’ configuration (Southall et al., 2011). The trawls are similar to those employed for the marine shrimp (Penaeus spp.) fishery, but they are geared in top-off position. The number of licenses issuable for the seabob trawl fishery is 22 (LVV Fisheries Department, 2013). Seabob shrimp are landed on ice at one of the two Surinamese processing companies (SAIL and Heiploeg Suriname) were the shrimp are peeled, graded, and frozen for export to Europe and the US. The industrial seabob shrimp fishery lands between 6,000 and 10,000 tons annually, making it the third highest producer of Atlantic seabob shrimp in the world (FAO, 2014). In the seabob trawl fishery off Suriname, as many as 40 different species of non-target catch might occur in a single haul (Southall et al., 2011). To reduce this unwanted bycatch, the fishery currently uses Turtle Excluder Devices (TEDs) with a 4” bar spacing and square-mesh panel Bycatch Reduction Devices (BRDs) with 150 mm stretched mesh size (LVV Fisheries Department, 2010) (Fig 1). The TEDs and BRDs were introduced in the seabob fishery in 1999 and 2009, respectively, and have proven to be quite effective in reducing bycatch. An evaluation of the square-mesh panel BRD has shown that it causes an average 34%-reduction in overall fish bycatch (by weight) (Polet et al., 2010). Bycatch of marine turtles is assumed to be negligible due to the use of TEDs (S. Hall, pers. comm.). Figure 1. Sketch of a trawl codend fitted with a square-mesh panel Bycatch Reduction Device (BRD) and super-shooter Turtle Excluder Device (TED) (source: Willems et al., 2016) 2 Despite the positive effects of TEDs and BRDs, an analysis of the catch composition in the seabob fishery has shown that bycatch still accounts for ca. 40% of the catch (by weight) in the seabob fishery (Willems et al., 2016b). Bycatch is dominated by fish (31 ± 14 % of the total catch), followed by jellyfish (8 ± 10 %) and benthos (benthic invertebrates; 2 ± 3 %). Only a small proportion of the bycatch (4% of the total catch) is utilized, with three fish species representing the bulk of the retained bycatch: Macrodon ancylodon (local name: bangamary/dagutifi), Cynoscion virescens (trout/kandratiki) and Nebris microps (butterfish/botrofisi). Whenever caught, prawns (Penaeus subtilis = brown shrimp) are also retained. Most of the bycatch in the seabob fishery, however, is discarded. Small “trash fish”, including juvenile individuals of the commercial species Cynoscion similis/jamaicensis (witwitie), C. virescens, M. ancylodon, N. microps and Ariidae spp. (catfishes) represent an important part of the discards. Discards also include several species of elasmobranchs (cartilaginous fishes) such as Dasyatis geijskesi (sharpsnout stingray), Dasyatis guttata (longnoze stingray), Urotrygon microphthalmum (smalleyed round stingray), Gymnura micrura (smooth butterfly ray), Dasyatis americana (southern stingray), Rhinoptera bonasus (cownose ray), Rhinobatos percellens (guitarfish) and Narcine bancroftii (electric ray) (Willems et al., 2016a; Willems et al., 2016b). Due to their life cycle characteristics, elasmobranchs are generally known to be vulnerable to fishing mortality (e.g. Graham et al., 2001; Goodwin et al., 2002; Fisher et al., 2013), and several species are therefore categorized as Endangered, Threatened or Protected (ETP) species. According to the IUCN Red List of Threatened Species, D. geijskesi and R. bonasus classify as “Near Threatened”, while the N. bancroftii is listed as “Critically Endangered” (IUCN, 2016). The impact of the seabob fishery on these stingray species has raised conservation concerns in the management of the fishery. Because it was unclear how frequently the rays occurred in the bycatch of the fishery, and to what degree the TED actually reduced their capture, a catch- comparison study was conducted in 2012-2013 (Willems et al., 2016a). It appeared that TEDs were efficient in excluding large-sized rays from the trawls, while smaller rays passed through the bars of the TED and ended up being caught. Hence, high escape ratios were observed for D. geijskesi (77%), a large-sized species, while exclusion of the small species U. microphthalmum was not significant. A size-dependent escape was observed for the two most abundant mid-sized ray species D. guttata and G. micrura. The study concluded that ray bycatch in the Suriname seabob fishery might be further reduced by introducing TEDs with reduced bar-spacing (Willems et al., 2016a). TEDs with reduced bar spacing (2” instead of 4”) have been successfully tested in shrimp fisheries in the Gulf of Mexico (Nalovic, 2014) and French-Guiana, where they are referred to as TTEDs (Trash-and-Turtle Excluder Devices) (Fig. 4 b and c) (Nalovic & Rieu, 2010; WWF, 2010). Based on these positive results, the Suriname Fisheries Department decided to conduct trials with TTEDs in the seabob trawl fishery. 3 The goal of this study is to evaluate the performance in bycatch reduction of TTEDs with 2” and 3” bar-spacing, against the standard 4” TEDs. More specifically, the study aimed to assess whether these TTEDs are effective in reducing elasmobranch bycatch, while retaining the target seabob shrimp catch. Further, the effect of TTEDs on retained bycatch was addressed. The study therefore aimed to answer the following questions: (1) Do TTEDs cause a reduction in overall bycatch? (2) Do TTEDs cause a reduction in bycatch of elasmobranch species? (3) Do TTEDs affect catches of seabob shrimp? (4) Do TTEDs affect catches of commercially valuable bycatch species? The result of this study will help to identify an optimal bar spacing for the TEDs in the Suriname seabob fishery, balancing bycatch reduction with retention of both target catch and valuable bycatch. This approach is in line with the Suriname Fisheries Management Plan 2014 – 2018 (LVV Fisheries Department, 2013), and with the goals of the project ‘Sustainable Management of Bycatch in Latin America and Caribbean Trawl Fisheries (REBYC-II LAC). The Suriname seabob fishery is certified by the Marine Stewardship Council (MSC) in 2011 (Southall et al., 2011). By investigating the potential of TTEDs in reducing bycatch, this study will help the fishery in optimizing the fishing gear and keep improving the fishery to comply with the MSC standards for sustainable fisheries. 2. Material and methods 2.1. Study area The study was carried out on commercial seabob fishing grounds which are delimited by the 10 and 15 fathoms depth contours and up to 18 fathoms in the eastern part of the shelf (LVV Fisheries Department, 2010). The experimental hauls were mainly performed in the eastern part of the study area (Fig. 2). 4 Figure 2. Study area with the location of the experimental hauls. Start locations of sampled hauls of July (3” TTED; red circles ) and of August (2” TTED; green squares ). 2.2. Sea trials and gear specifications The experimental catch-comparison hauls were performed during two fishing trips, on board FV Neptune-6 (1-6 July 2016) and FV Sechong-29 (9-12 August 2016). Both vessels are typical ca. 20m-long, 425 hp ‘Florida-type’ outrigger trawlers of the seabob shrimp trawling fleet. They are equipped for quad-rig bottom trawling, dragging a double trawl at both starboard and port side (Fig. 3). The trawls had a vertical opening of ca. 2 m and tickler chains attached to the footrope. Mesh size of the trawls ranged from 57 mm in the body and wings of the trawl to 45 mm in the codend (Willems et al., 2016b). 5 Figure 3. The quad-rig trawl configuration as used in the Suriname seabob fishery. The outer codends (1 and 4) are used for the side-by-side catch comparisons. The inner two codends (2 and 3) are not used because the try-net (5) might interfere with the catches in these trawls. Figure adapted from Eayrs, 2012. 5 Besides the four main trawls, the seabob fishery uses a try-net to assess potential shrimp catches before and during fishing operation. The try-net, however, might interfere with the catches of the inner codends (2 and 3). Therefore, only the outer codends (1 and 4) were used in the catch comparison experiments (Fig. 3). One of the outer codends was modified to fish as experimental codend by replacing the standard TED with a TTED. Because port and starboard trawls rarely fish with an identical efficiency, the experimental codend was regularly switched between trawl 1 and 4 to cancel out these port/starboard effects. An equal amount of hauls was completed with the experimental codend fitted to trawl 1 and 4. Apart from the replacement of the standard TED by a TTED, the sea trials were done under commercial fishing circumstances, implying that aspects like vessel type, fishing gear, trawling speed, etc.
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