Pacheco-Aldana, P., S., Ortega-García, L.A., Abitia-Cárdenas, U., Jakes-Cota, A., Tripp-Valdez & A., Preti (2024). Seasonal and ontogenic differences in the trophic spectrum of the striped marlin Kajikia audax (Philippi, 1887) in Cabo San Lucas, Baja California Sur. 74th Annual Tuna Conference. Lake Arrowhead, California, Estados Unidos de América, mayo 20 - 23, 2024, 1.
Pamela Pacheco-Aldana 1, Sofía Ortega-García 2, Leonardo Andres Abitia-Cárdenas 1, Ulianov Jakes-Cota 1, Arturo Tripp-Valdez 1 y Antonella Preti 3
Striped marlin (Kajikia audax) is important for recreational fishing in Cabo San Lucas, B.C.S., Mexico. Previous studies have described trophic ecology with analysis of stomach contents or stable isotope analysis. This study aims to apply both methods with the ultimate goal of characterizing changes due to sex, ontogenetic development (young and adults), and season (warm and cold). To achieve this goal, a total of 519 stomachs collected from the Cabo San Lucas sport fishing fleet will be processed from 2019 to 2022. To date, 239 stomachs have been successfully analyzed, of which 83% contained prey. The total length of the organisms ranges between 140 cm and 242 cm in general. Currently, there are 82 prey items reflected in the diet. To date, the Prey Specific Index of Importance (%PSIRI) has yielded preliminary results. Across all categories, cephalopods dominate the diet with fishes closely following in importance. In general, the Humboldt squid Dosidicus gigas (46%), Pacific Mackerel Scomber japonicus (17%), Auxis spp. (8.7%), Sardinops sagax (4.4%), and Argonauta spp. (4.3%) were the most important species. Female striped marlin mainly consumed D. gigas (43%), S. japonicus (25.9%), S. sagax (5.6%), Auxis spp. (4.9%), and Argonauta spp. (4.1%). Males primarily consumed D. gigas (46%), S. japonicus (13%), Auxis spp. (10%), Lagocephalus lagocephalus (5.3%), and Argonauta spp. (4.3%). The juvenile males (lengths = 188 cm) and juvenile females (lengths = 197 cm) principally consumed D. gigas (33%), Argonauta spp. (25%), Balistes polylepis (11%), Auxis spp. (7%), S. japonicus (5.3%). Adult males (lengths = 189 cm) and adult females (lengths = 198 cm) principally consumed D. gigas (36%), Argonauta spp. (26%), S. japonicus (20%), S. sagax (3%), L. lagocephalus (2.5%). Diet in the warm season consisted of D. gigas (36%), B. polylepis, (16%), Argonauta spp. (14%), Auxis spp. (7.7%), L. lagocephalus (5.3%). Diet in the cool season consisted of Argonauta spp. (38%), S. japonicus (31%), D. gigas (16%), S. sagax (10%), Auxis spp. (0.5%). Diet differences in the warm and cold season were found (R = 0.103, p = 0.01). The other categories were not found to have differences. These preliminary results suggest the following preliminary conclusions. The striped marlin tends to pursue similar cephalopod and fish species when they are available regardless of sex and maturity. The diet may change between cool and warm seasons due to prey item migrations in response to environmental conditions. Future work entails preparation of approximately 110 muscle samples for stable isotope analysis. The prepared samples will be sent for analysis at University of California Davis and results will be expected in late May or early June for further statistical analysis and interpretation.
Palabras clave: Striped marlin; feeding habits; sport fishing fleet; Cabos San Lucas; Mexico
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