Temporal and latitudinal comparisons of reproductive parameters in a heavily exploited shark
29. March 2020
Temporal and latitudinal comparisons of reproductive parameters in a heavily exploited shark, the bonnethead, Sphyrna tiburo (L. 1758), in the southern Gulf of Mexico
D. Palacios‐Hernández, J.L. Castillo‐Géniz, I. Méndez‐Loeza, J.C. Pérez‐Jiménez
ABSTRACT:
In the southern Gulf of Mexico, the bonnethead shark, Sphyrna tiburo, is one of the most frequently captured species in landings of small‐scale fisheries. Based on the analysis of two fishery‐dependent sampling periods (1993–1994 and 2007–2014), this study aimed to determine reproductive parameters and identify temporal differences between the two time periods. In the first sampling period (FSP), 776 males and 352 females with a size range of 28.0–120.0 cm LT were analyzed, and in the second sampling period (SSP), 387 males and 432 females, with a size range of 28.0–122.0 cm LT were analyzed. The size at 50% maturity in SSP was significantly different between sexes, 82.6 cm LT for females and 73.8 cm LT for males (no estimation was possible for FSP). The size at 50% maternity was not different between sampling periods, 97.3 cm LT for FSP and 99.0 cm LT for SSP. Litter size varied from 3 to 19 embryos and the average was not statistically different in both periods, 10.1 (S.D. = 3.8) for FSP and 11.3 (S.D. = 3.5) for SSP. The female reproductive cycle is asynchronous, and it seems to be annual, with a gestation period of 5 to 6 months, and a consecutive ovarian cycle and gestation period. Temporal (between sampling periods) and latitudinal (southern Gulf versus northern regions) variations occur in synchronicity of the reproductive cycle, temporal variation in the relationship between maternal length and litter size, and latitudinal variation in average size of mature sharks.
Fish Biology, DOI 10.1111/jfb.14330