Hábitos alimenticios de Scomber japonicus en el golfo de Guayaquil
Fecha
2020-10
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Facultad de Ciencias Naturales. Universidad de Guayaquil
Resumen
Scomber japonicus es una especie ampliamente capturada en el Ecuador, de gran interés comercial, por lo tanto, es importante analizar las redes tróficas para establecer las bases nutricionales del recurso en función de los hábitos alimenticios de Macarela en el golfo de Guayaquil. Por esta razón, se determinó su composición dietaria a partir de 187 muestras provenientes del Crucero de prospección INP 2019-12-02 de diciembre 2019 y muestras del programa de observadores pesqueros en agosto 2020. Se estableció la estructura de tallas y se estimaron índices de digestión, repleción, importancia relativa (%IIR) e importancia geométrica (GII), así como, su amplitud de dieta (índice de Levin) y su nivel trófico (TROPH). Los 187 organismos analizados presentaron rangos de tallas entre 21 - 34 cm LT, de los cuales 56 fueron hembras, 115 machos y 16 organismos sin identificación de sexo. La captura mostró una concentración entre las tallas 23 - 26 cm LT, conformado en su mayoría por machos debajo de la talla de madurez sexual (26 cm). De los estómagos analizados el grado de repleción predominante fue el de 25 % (semivacíos) y el grado de digestión más frecuente correspondió al G1. La composición dietaria de S. japonicus estuvo constituida por 29 ítems presas, donde el %IIR muestra una predilección alimenticia hacia los Actinopterygii (37%), huevos de invertebrados (35%), y en menor medida hacia el fitoplancton (23%) y zooplancton (5%). Finalmente, se definió a S. japonicus como un depredador especialista (Bi = 0,2), estableciendo su posición trófica como una especie carnívora secundaria – terciaria (Troph = 3); sin embargo, se observó un cambio ontogénico en la dieta, pasando de una dieta omnívora hacia una dieta con tendencia carnívora.
Scomber japonicus is a species widely captured in Ecuador of high commercial interest; therefore it is important to analyze the food webs to establish the nutritional basis of the resource according to the feeding habits of Macarela in the Gulf of Guayaquil. For this reason its diet composition was determined from 187 samples obtained from the Survey Cruise INP 2019-12-02 in December 2019 and from the Fisheries Observer Program in August 2020. The size structure was determined, as well as, digestion, repletion, relative importance (% IIR), and geometric importance (GII) indices. Besides, the diet range (Levin's index) and trophic level (TROPH) were estimated too. The 187 individuals analyzed had size ranges between 21 - 34 cm TL, of which 56 were females, 115 were males, and 16 organisms without sex identification. The catchment showed a concentration between sizes 23 - 26 cm TL, made up mostly of males below sexual maturity length (26 cm). Of the stomachs analyzed, the predominant degree of repletion was 25% (semi-empty) and the most frequent degree of digestion corresponded to G1. The dietary composition of S. japonicus consisted of 29 prey items, where the %IIR showed a dietary predilection towards Actinopterygii (37%), invertebrate eggs (35%), and to a lesser extent towards phytoplankton (23%) and zooplankton (5%). Finally, S. japonicus was defined as a specialist predator (Bi = 0,2), establishing its trophic position as a secondary - tertiary carnivorous species (Troph = 3); however, an ontogenetic change in diet was observed, switching from an omnivorous diet to a diet with a carnivorous tendency.
Scomber japonicus is a species widely captured in Ecuador of high commercial interest; therefore it is important to analyze the food webs to establish the nutritional basis of the resource according to the feeding habits of Macarela in the Gulf of Guayaquil. For this reason its diet composition was determined from 187 samples obtained from the Survey Cruise INP 2019-12-02 in December 2019 and from the Fisheries Observer Program in August 2020. The size structure was determined, as well as, digestion, repletion, relative importance (% IIR), and geometric importance (GII) indices. Besides, the diet range (Levin's index) and trophic level (TROPH) were estimated too. The 187 individuals analyzed had size ranges between 21 - 34 cm TL, of which 56 were females, 115 were males, and 16 organisms without sex identification. The catchment showed a concentration between sizes 23 - 26 cm TL, made up mostly of males below sexual maturity length (26 cm). Of the stomachs analyzed, the predominant degree of repletion was 25% (semi-empty) and the most frequent degree of digestion corresponded to G1. The dietary composition of S. japonicus consisted of 29 prey items, where the %IIR showed a dietary predilection towards Actinopterygii (37%), invertebrate eggs (35%), and to a lesser extent towards phytoplankton (23%) and zooplankton (5%). Finally, S. japonicus was defined as a specialist predator (Bi = 0,2), establishing its trophic position as a secondary - tertiary carnivorous species (Troph = 3); however, an ontogenetic change in diet was observed, switching from an omnivorous diet to a diet with a carnivorous tendency.
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ACTINOPTERYGII, POSICIÓN TRÓFICA, HÁBITOS ALIMENTICIOS