Worbis-Badias, M., U., Jakes-Cota, S., Ortega-García & R., Rodríguez-Sánchez (2023). Otoliths, spines reading and multi-model inference for ageand growth estimation of the striped marlin (Kajikia audax) in Baja California Sur. 73rd Annual Tuna Conference. LAKE ARROWHEAD, CALIFORNIA, Estados Unidos de América, mayo 22 - 25, 2023, 41.
Mariana Worbis-Badias 1, Ulianov Jakes-Cota 1, Sofía Ortega-García 1 y Rubén Rodríguez-Sánchez 1
The striped marlin (Kajikia audax) is the main target species of the sport fishery that operates off Cabo San Lucas, Baja California Sur (CSL), Mexico, which contributes 80% of the marlin species catch. Previous studies on the striped marlin age have been based on counting the annual growth marks on the dorsal spine fin. This research uses the combination of spines and otoliths of fish under one year of age in a first step; counting the daily growth marks on their otoliths are counted, associating the average diameter of the first annual mark on their dorsal spines. In a second step, with this average diameter, the count of growth marks in the spines of older fish was corrected, since errors could occur in the assigned ages due to the vascularization of the center of the spines. Monthly biological sampling of the sport-fishing fleet landings was conducted in CSL from 2015 to 2022. A total of 739 organisms (358 females, 381 males) were sampled. The lower jaw fork length (LJFL), total weight, and sex were recorded for each fish. The fourth dorsal-fin spine (357) and sagittal otoliths (198) were extracted. The LJFL range for females was 132-242 cm with an average length of 187.3 cm, and 133-228 cm with an average length of 183.7 cm for males. The average size by sex showed significant differences (p = 0.0027), contrary to the length-weight relationship where no significant differences were found (p = 0.5084). The Student's t-test indicated that b-value for combined sexes was not significantly different (p > 0.05) from the theoretical value of isometric growth. The results showed two to nine growth marks in transverse sections of the dorsal-fin spine and up to 247 daily micro-increments in polished otolith sections of younger organisms (= 170 cm LJFL). The individual growth parameters of the von Bertalanffy model of young organisms estimated with the LJFL data and daily mark counts on otoliths were: ????8 = 164.16, k = 2.1, and t0 = - 1.87. An average LJFL of 164 cm and an average diameter of the cross sections from spines of 0.88 cm were estimated at the first annual growth mark. This estimation determined that the sport-fishing fleet caught in six age groups (0-5 years). According to the Akaike information criterion, von Bertalanffy´s model (????8 = 226.92 cm, k = 0.49, t0 = -1.66) best represents the individual growth of striped marlin, which indicates accelerated growth in the early years of life of striped marlin, reaching up to 82 % of its asymptotic length in the second year.
Palabras clave: Otoliths; age and growth; Striped marlin
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