Feeding habits of the fishes Euthynnus lineatus and Scomberomorus sierra (Perciformes: Scombridae) in the Eastern Tropical Pacific

Abstract

ABSTRACT. Introduction: Black skipjack, Euthynnus lineatus, and Pacific sierra, Scomberomorus sierra, are of great economic importance in the small-scale fishery of the Tropical Eastern Pacific and in particular in the study area. Objectives: The objectives of the present study were to assess the diet components of E. lineatus and S. sierra, as well as to evaluate the niche width, trophic level, and trophic overlap between the two species, by size and season. Methods: Biological samples were obtained weekly from small-scale fishery catches in Bahía de Acapulco, Mexico. The E. lineatus sampling period occurred from October 2016 to October 2017, whereas S. sierra was sampled from October 2016 to June 2018. The Prey-specific Index of Relative Importance (% PSIRI) was used to evaluate the importance of each prey item in the diet of the predator. Levin´s index (Bi) was used as a measure of niche width. The Morisita-Horn index was used to evaluate diet overlap by size (juveniles or adults), by season (dry or wet), and between the two species. The trophic level (TL) of predators was calculated using the Cortés´ method. Results: A total of 262 E. lineatus stomachs were analyzed (42 % were empty and 58 % contained food) and a total of 209 S. sierra stomachs were analyzed (74.6 % were empty and 25.3 % contained food). Of the total E. lineatus specimens sampled, 107 were juveniles and 155 were adults. Black skipjack juveniles fed on five food items and adults fed on 13 food items. Of the total S. sierra specimens sampled, 75 were juveniles and 134 were adults. Pacific sierra juveniles and adults fed on five food items. The diet of the two species comprised fish, mollusks, and crustaceans. The two species showed narrow niche width. The diet of juvenile and adult E. lineatus presented differences with growth, contrary to what was observed for juveniles and adults of S. sierra. There were no significant differences in diet by season for both species. The trophic overlap obtained between the two species was low. The trophic level calculated for both species indicated that are tertiary consumers. Conclusions: Black skipjack and Pacific sierra are tertiary predators and present a specialist behavior, feeding mainly on fish from the families Engraulidae and Clupeidae. Although a degree of similarity in the dietary food components of these species was observed, there was not a high degree of interspecific competition for food.

Ectoparasitic community of the gills of Pacific sierra Scomberomorus sierra Jordan & Starks, 1895 (Actinopteri: Scombridae) from northern Peru

“…However, all that has been published to date in the scientific literature does not show differences in the ecological relationships (habitat, behavior, and feeding) of males and females of S. sierra and does not help us to adequately explain the differences found between the sex of the host and the ecoparasitological parameters of T. crocea and Didymocylindrus sp. (Sandoval-Ramírez et al, 2020;Torres-Rojas et al, 2020). This interpretation would also apply the differences observed for the parasitological indices of (Iannacone et al, 2013;Rey et al, 2022).…”

“…The high vagility and endothermy of scombrids require the need for high metabolic energy which is met by foraging large quantities of food items (e.g., crustaceans, fish of the Engraulidae and Clupeidae families, molluscs, and finally, polychaetes) and can function as intermediate and paratenic hosts for didymozoids. This indicates that this species act as tertiary consumers, or mesopredators, in the food network (Miranda-Delgado et al, 2019;Sandoval-Ramírez et al, 2020). The high prevalence and medium abundance levels of Didymocylindrus sp., could be explained by the preference of S. sierra to prey on fish (Moreno et al, 2011), since these actinopterygians are intermediate or paratenic hosts for didymozoids of this group of trematodes (Bárcenas et al, 2021).…”

Length-weight relationship and condition factor of bullet tuna (Auxis rochei Risso, 1810) in the waters of Mamuju District, West Sulawesi Province, Indonesia

“…Bullet tuna, classified in the Scombridae family, is an epipelagic fish discovered in worldwide distribution, particularly in tropical waters (Sandoval-Ramírez et al 2020;Mardlijah et al 2021). Furthermore, it is a major target during fishing activities (Ollé-Vilanova et al 2022) and holds high economic value due to its nutritional content.…”