Aggregations and reproductive events of the narrownose smooth-hound shark, Mustelus schmitti, in relation to temperature and depth in coastal waters of the south-western Atlantic Ocean (38?42°S)

COLONELLO JORGE; SOMOZA GUSTAVO; ELISIO MARIANO; JAUREGUIZAR ANDRÉS; CORTÉS FEDERICO; MACCHI GUSTAVO

MARINE AND FRESHWATER RESEARCH

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2017 vol. 68 p. 732 - 742

1323-1650

Knowledge ofenvironmental influence on reproductive dynamics in chondrichthyans is criticalfor effective management. The present study assessed the potential influencesof temperature and depth on aggregations and reproductive events of thenarrownose smooth-hound shark (Mustelusschmitti), using an analysis criterion based on the co-occurrence ofdifferent reproductive stages. Data were collected from 363 sample sites duringsix research surveys, covering an area of ~13 920 nm2along the coast (38?42°S, depth of <50 m). Aggregations M. schmitti adults were mostly associated with the warmer springsurveys, with the aggregation sites being significantly warmer than those of non-aggregation.Evidence of pupping and ovulation was observed, almost simultaneously, duringall spring surveys. However, the occurrence of these reproductive events showeda clear interannual variability pattern that was significantly explained bywater temperature. Particularly, the occurrence of ovulation was associatedwith temperatures above 16?17°C. These results suggest that M. schmitti adults may follow thewarming gradient along the environment and, thus, they aggregate in shallow andproductive waters during the course of spring. Their reproductive events couldbe induced by temperature increase. This scenario suggests that changes in thepatterns of bottom temperature may be important drivers of the reproductivedynamics of M. schmitti.The present studyprovided evidence of interannual changes in the M. schmitti reproductive aggregation patterns in coastal waters ofthe south-western Atlantic Ocean, associated with different bottom-temperatureregimens, depending on depth. The M. schmittireproductive aggregations, observed during spring, were associated withtemperatures above 16?17°C, which occurred mainly in shallow waters. Theresults suggested that changes in depth-dependent bottom-temperature patterns maybe important drivers of the reproductive dynamics of this species.