Trophic niche of the Pacific Sierra (Scomberomorus sierra) in the southeastern Gulf of California: Assessing its importance as a predator and prey (Mesopredator) in the food web

Abstract

The identification of interspecific links (trophic niche) is important to characterize resource use of a predator, and to know its trophic role (for example, mesopredator or top predator) in the food web. In this study, we examined: a) the trophic ecology of Scomberomorus sierra as a predator (niche breadth, trophic overlap, and trophic position) and b) its presence as a prey in the diets of the region´s top predators, to evaluate the critical link of S. sierra as a probable mesopredator in the food web of the southeastern Gulf of California (GC). Based on %PSIRI, the dominant diet of S. sierra were engraulids and cephalopods. The diet was similar between sexes and among size‐classes. However, the isotopic niche breadth values and δ15N variance (>1) reflect a broad niche for young adults likely related to a) changes in morphology (e.g., size of the mouth), b) development of the visual system, and c) changes in the energy requirements of the species reproductive stages. Seasonal changes in prey species’ availability and abundance resulted in isotopic variations, indicating that S. sierra is an opportunistic predator. A wide range in trophic position value (from 3.8 to 4.2) indicated that it also is an intermediary carnivore, with a high degree of trophic plasticity. Although S. sierra has not a dominant role in top predators’ diets, they share some prey species such as anchovies and other fish, depending on predator size. Therefore, S. sierra is a species with many prey‐predator relationships in the southeastern GC food webs that may be considered a critical trophic link. This information is crucial for an ecosystem‐based fisheries management in the Gulf of California.

Ontogenetic shifts in feeding habits of orangemouth weakfish (Cynoscion xanthulus): From estuarine benthic feeder to marine nektivore top predator

“…This could also indicate that the sources of carbon differ between both habitats, as estuarine organisms have increased assimilation of autochthon δ 13 C primary producers in the base of their food web, whilst large marine organisms reflect marine basal sources of δ 13 C, which are larger values when compared to estuarine and freshwater environments (Bouillon et al, 2008). The values found in our study are similar to other estuarine benthic feeders in the case of small juvenile organisms, and large nektonic predators, as in the case of large marine orangemouth weakfish (Torres‐Rojas et al, 2020).…”

“…The change in habitat is reflected in its diet, as small individuals prey on estuarine benthic and demersal fauna, and large organisms feed exclusively on nekton prey (squid and pelagic fish). This change in prey selection can be related to the development of the visual system, as well as changes in the energy requirements of the species' reproductive stages (Torres‐Rojas et al, 2020). It is known that body length plays a central role in predator–prey interactions (Sheldon et al, 1977), and the different isotopic composition of the transition from juvenile to adult orangemouth weakfish might be reflective of differences in feeding strategies associated with the increase in size and the change of habitat.…”

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

“…In other studies, no significant differences were found for the P% and MI of Didymocylindrus filiformis Ishii, 1935 between the sexes of scombrid K. pelamis (Silva et al, 2017). Our results are surprising, because biological differences between males and females of S. sierra have not previously been reported in the literature (Aguirre-Villaseñor et al, 2006;Lucano et al, 2011;Espino-Barr et al, 2017;Justo & Kohn, 2014;Torres-Rojas et al, 2020). Thus, there is a clear indication of the prefer-ence of the parasites for one of the sexes of the host fish.…”

“…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).…”

“…This pattern is opposite to that observed in other fish species, in which larger fish can facilitate parasite colonization by ecto-and endoparasites because larger fish offer a greater surface area for gill-attaching parasites, tend to ingest larger amounts of food, and are often older, meaning they have had more time to accumulate parasites than smaller, younger individuals (Miranda-Delgado et al, 2019). Differences in the diet of S. sierra have been reported among the different size classes of these fish (juveniles, pre-adults and adults) (Torres-Rojas et al, 2020).…”