Diet and histological features of digestive tube from four discarded fish species by trawl bycatch in Northeastern Brazil

Abstract

Fish feeding habit associated to the morphology of their digestive tube can provide useful biological and ecological information. Between January and December 2012, we examined 16 fish species discarded by trawl in the Potiguar basin, northeastern Brazil, and classified them into four groups according to Alimentary Index - IAi. Our aims were to: (1) provide information on diet composition of one species represented by each group (Opisthonema oglinum, Conodon nobilis, Larimus breviceps and Sphoeroides testudineus), (2) examine the morphology of their digestive tube, and (3) associate ingested food items with the morphological features. Stomach contents were collected and classified according to IAi: main, accessory and secondary categories; fragments of esophagus, stomach, and small intestine were examined using paraffin section technique. Biometric data (total length-TL, standard length-SL and total weight-TW), stomach weight-SW, and gonadal weight-GW were recorded and applied in two indices: (1) the stomach Repletion Index - SRI (SRI = SW/TW × 100) and (2) the gonadosomatic index - GSI (GSI = GW/TW × 100) for the analyses of feeding and reproductive activities, respectively. The main food categories were (1) Teleostei for C. nobilis, (2) Crustacea for L. breviceps and O. oglinum, and (3) Mollusca for S. testudineus. The feeding activity was higher during the dry season, while the GSI was higher in the rainy season. The morphological analysis revealed a regular structure of the tissues analyzed. We highlight the presence of tubular gastric glands and strong muscular walls in the stomach (O. oglinum; L. breviceps); well-developed pyloric caecum in the intestine (O. oglinum; C. nobilis; L. breviceps); and presence of pseudo-stomach (S. testudineus). Our study confirms that the digestive tube of the examined species has morphological adequacy for carnivorous feeding habit, providing useful information on tissue structures associated to diet composition.

Ecomorphological relations of sympatric juveniles of Clupeiformes from a Brazilian sandy beach

“…These variables are directly related to the body stretching and to the ability to feed on bigger prey items (Gatz, 1979;Watson & Balon, 1984). This not only morphologically differentiated these clupeids, for being species of carnivorous food habit, but also showed differences between them, since H. clupeola presents a more planktivore habit than O. oglinum which has a feeding preference for crustaceans (Vega-Candejas et al, 1997;Chaves & Vendel, 2008;Soares et al, 2018;Favero et al, 2019;Bomfim et al, 2020).…”

Dietary metabarcoding of keystone sardine species reveals the importance of their ichthyoplankton prey in food webs of the Southern Brazilian Bight fisheries

“…In our study, fish were identified as the dominant source of prey for S. brasiliensis , but the pteropod mollusk C. virgula was also found. The dorosomatid O. oglinum has also been described as having a feeding preference for crustaceans (Bomfim et al, 2020; Couto & de Vasconcelos Filho, 1986; de Chaves & Vendel, 2008; Olher & Gasalla, 2023; Vega‐Cendejas et al, 1997), but some of the cited studies found food items that were only classified as “unidentified fish” (Couto & de Vasconcelos Filho, 1986; Vega‐Cendejas et al, 1997), or Teleostei remains (scales and bones), otoliths, juveniles, or animal matter (Bomfim et al, 2020; Olher & Gasalla, 2023). In our study, fish were identified as the dominant source of prey for O. oglinum , though some invertebrates ( P. avirostris and C. virgula ) were also detected in its diet.…”

Stock assessment of Larimus breviceps, a bycatch species exploited by artisanal beach seining in Northeast Brazil

“…The relative fishing mortality of shorthead drum we estimated differed from a similar study (García & Duarte, 2006), likely because fishing strategies differed. The use of motorized trawling as a fishing method may have a detrimental impact on shorthead drum stocks (Bomfim et al, 2019). Moreover, differences in Z estimated by Bessa et al (2013) might have been influenced by the sampling method, which primarily targeted juveniles in a limited range of the shorthead drum distribution.…”

“…Its distribution spans the West Atlantic region from Costa Rica to Santa Catarina in Brazil (Cattani et al, 2011). The shorthead drum holds significant socioeconomic importance, as bycatch and a food source for fishing crews and local communities (Bomfim et al, 2019; Lira et al, 2022; Silva‐Júnior et al, 2019). In artisanal beach seining fisheries in Brazil, this species can comprise up to 28% of total biomass (Freitas et al, 2011; Santos et al, 2021).…”