LLadó-Cabrera, D., S., Aguiñiga-García, L., Carreón-Palau, F., Galván-Magaña, R., González-Armas & A., Tripp-Valdez (2025). Food partitioning, trophic niche, and fatty acid composition and trophic retention in co-existing threatened sharks with different feeding strategies. Food webs. 45: e00427. DOI: 10.1016/j.fooweb.2025.e00427.
Dayli LLadó-Cabrera 1, Sergio Aguiñiga-García 1, Laura Carreón-Palau 2, Felipe Galván-Magaña 1, Rogelio González-Armas 3 y Arturo Tripp-Valdez 1
Predators like sharks play critical roles in marine and coastal ecosystems and shark population declines can have a variety of unexpected and disruptive effects on these ecosystems. To understand the food web associated with artisanal fishing of sharks, we analyzed the partitioning of food resources and the trophic retention of essential nutrients (e.g., fatty acids) in Sphyrna lewini, Squatina californica, and Rhizoprionodon longurio, three shark species with critically endangered, near threatened and vulnerable status, respectively, in the IUCN red list that coexist in a subtropical bay, the Bahía de La Paz, Baja California Sur, Mexico. We estimated short-term food partitioning using their diet analyzed by stomach contents. We evaluated the effect of stomach contents partitioning on the trophic niche, and profiles and concentration of essential fatty acids. The Prey-Specific Relative Importance Index showed that S. lewini has a more diverse diet. Although the three species of sharks share some prey items such as the Pacific mackerel Scomber japonicus, PERMANOVA analysis determined that the diet of these sharks is significantly different. There is low similitude of stomach content ranging between 2 and 5 %. R. longurio had the largest isotopic niche space obtained with Bayesian standard ellipse areas. Also, results of nicheROVER shows that R. longurio had higher mean probability of niche overlap with S. lewini (66 %), than with S. californica (46 %). Similarly, the greatest mean probability of niche overlap for S.californica was with R. longurio (88 %), while the mean probability of overlap in isotopic niche space was 40 % between the S. californica and S. lewini. Also, the high directional overlapping or low degree of partitioning of the isotopic niche between S. lewini and R. longurio was coincident with not significant difference in fatty acid profiles. Fatty acids profile similitude ranged between 76 and 89 %. These differences were found in the fatty acid profiles and concentrations. S. californica showed a higher separation from S. lewini and the lowest trophic retention of EPA and DHA. These observations suggest differences in metabolic requirements in S. californica or that with its ambush strategy, they obtain less food as they depend on finding ideal ambush sites.
Palabras clave: stable isotopes; essential fatty acids; Niche differentiation; Partitioning; Sharks
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