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FISH SPECIES CAUGHT BY SHRIMP TRAWLERS OFF THE COAST OF SERGIPE, IN NORTH-EASTERN BRAZIL, AND THEIR LENGTH–WEIGHT RELATIONS

Abstract. The objective of this study was to report all fish species caught by shrimp trawlers based in Pirambu, in the state of Sergipe, Brazil and estimate the length–weight relation (LWR) for the most abundant species in the samples. Four samples were collected monthly from four shrimp trawlers. A total of 8522 fishes were caught (89 species; 38 families). LWRs were estimated for 18 species having the parameter b within the range of 2.5–3.5: Cathorops spixii (Agassiz, 1829); Stellifer brasiliensis (Schultz, 1945); Pellona harroweri (Fowler, 1917); Odontognathus mucronatus Lacepède, 1800; Paralonchurus brasiliensis (Steindachner, 1875); Stellifer rastrifer (Jordan, 1889); Isopisthus parvipinnis (Cuvier, 1830); Selene brownii (Cuvier, 1816); Anchoa spinifer (Valenciennes, 1848); Trinectes paulistanus (Miranda Ribeiro, 1915); Symphurus plagusia (Bloch et Schneider, 1801); Chirocentrodon bleekerianus (Poey, 1867); Stellifer stellifer (Bloch, 1790); Citharichthys spilopterus Günther, 1862; Ctenosciaena gracilicirrhus (Metzelaar, 1919); Anchoviella lepidentostole (Fowler, 1911); Peprilus crenulatus Cuvier, 1829; Genyatremus cavifrons (Cuvier, 1830). Five new maximum size records were reported in this study for Trinectes paulistanus, Citharichthys spilopterus, Anchoviella lepidentostole, Chirocentrodon bleekerianus, and Stellifer brasiliensis. Fifty-four new maximum weight records were also registered. LWR estimated here are the first for Genyatremus cavifrons and Peprilus crenulatus.


INTRODUCTION
Length-weight relations (LWR) are used to estimate the weight corresponding to a given length, which reflects different conditions for various populations throughout their life cycle (Wootton 1998, Freire et al. 2009). LWRs and their parameter b are not considered interesting science for some fisheries scientists (Hilborn andWalters 1992, Froese 2006), even though these relations are important for estimating biomass where weighing fishes is not possible (Macieira and Joyeux 2009) or for species where such relations were not previously known (Froese 2006). Although LWRs have been estimated for many fish species along the Brazilian coast, data are still missing for many species, especially those that are not commercially important, or localities (Freire et al. 2009). This paper aims to identify all fish species caught by shrimp trawlers off the coast of Sergipe and estimate LWRs for the most abundant species.

MATERIAL AND METHODS
Samples were collected from the artisanal shrimp trawl fishery based in the municipality of Pirambu, in the state of Sergipe (Fig. 1). Four samples were obtained monthly from March 2015 to May 2016, with the exception of April and December 2015 and April 2016 due to two closed seasons per year for the shrimp fishery (90 days in total). Each sample, with approximately 6 kg, was separated immediately after the last trawl before heading to the port and was stored on ice and later kept frozen * Correspondence: Dr Kátia M. F. Freire, Laboratório de Ecologia Pesqueira (LEP), Departamento de Engenharia de Pesca e Aquicultura (DEPAQ), Universidade Federal de Sergipe (UFS), Rodovia Marechal Rondon, S/N, Jardim Rosa Elze, São Cristóvão, Sergipe, 49100-000 Brazil, phone: +55 79 3194 7401, e-mail: at the Laboratório de Ecologia Pesqueira da Universidade Federal de Sergipe (LEP/UFS) until further processing. All fish species collected here were identified and catalogued at LEP/UFS collection. Additional specimens were sent to the Acervo Zoológico da Universidade Santa Cecília (AZUSC/UNISANTA).
Total length (TL, cm) and total weight (TW, g) of each specimen were determined using an ichthyometer (precision: 1 mm) and a digital scale (precision: 0.1 g), respectively. Length-weight relations TW = a • TL b were estimated for all species with the sample size larger than 20 and with the maximum observed length corresponding to more than 70% of the maximum size reported in FishBase (Froese and Pauly 2018) or significantly higher than the length at first maturity (L m ). A linear regression was applied to the logarithm of both length and weight to estimate the parameters a and b and their respective confidence intervals were calculated. A t-test was used to determine if b was statistically different from 3 (α = 0.05).
The occurrence of the fish species reported in this study for the state of Sergipe was compared with existing information available in FishBase as well as their LWRs. FishBase is the largest online encyclopaedia of fishes and contains information on 34 000 species (Froese and Pauly 2018), based on scientific publications, which has been increasingly cited in the scientific literature (Stergiou and Tsikliras 2006).

DISCUSSION
Freire and Araújo (2016) listed commercial fish species for the state of Sergipe. Thirty species are also listed here, indicating they are, in fact, commercially important. Juveniles of important species correspond to a high proportion of the bycatch of shrimp trawlers and species without market value are probably discarded or consumed by fishers (Tischer andSantos 2001, Branco 2005). Thus, a high proportion of the catch may not be accounted for in officially reported catch statistics. It is also worth pointing out that many species reported here were never registered in previous studies carried in the area related to the bycatch of shrimp trawlers in the state of Sergipe (Santos 1996    All results for b from the LWR are within the usual range (2.5-3.5) described by Carlander (1969). Species for which only juveniles were sampled were excluded from this analysis as small individuals change during growth (Lima Filho et al. 2006), resulting in very different b values. These values may also be influenced by differences among seasons (Pauly 2010), localities, and feeding habits (Wootton 1998). This is the first time that an LWR is presented for G. cavifrons, and P. crenulatus under their revised scientific names (Tavera et al. 2011, Marceniuk et al. 2016). n = number of individuals, TL = total length observed, TL max = total length reported in FishBase, L m = length at first maturity reported in FishBase; a and b = parameters of the LWR, SE = standard error, r 2 = coefficient of determination; only species with more than 20 specimens examined and the maximum observed length representing more than 70% of the maximum size reported in FishBase (Froese and Pauly 2018) or significantly higher than L m are presented; 1 no LWR found for Brazil, 2 LWR not found for NE Brazil; 3 new species name according to Tavera et al. (2011) and Marceniuk et al. (2016), 4 TL max obtained in this study higher than currently reported in FishBase, 5 b statistically different from 3.