Abstract

REYES-BONILLA, Héctor; RAMIREZ-ORTIZ, Georgina; HERRERO-PEREZRUL, María Dinorah  and  CALDERON-AGUILERA, Luis E.. Underestimation of the abundance of brown sea cucumber Isostichopus fuscus (Holothuroidea: Echinodermata) in daylight compared to nighttime surveys in the Gulf of California. Rev. Mex. Biodiv. [online]. 2016, vol.87, n.2, pp.519-522. ISSN 2007-8706.  https://doi.org/10.1016/j.rmb.2016.05.004.

The brown sea cucumber Isostichopus fuscus, is a holothurid with high commercial value. In Mexico it is federally protected, and the fishery in the Baja California Peninsula follows management actions established by technical committees, on the basis of agreements among government agencies, scientists and organized fishermen. One of these agreements is that evaluations of its abundance must be done during the day, as it has been suggested that during daylight hours the organisms hide inside holes, resulting on lower values, but this has not been demonstrated yet. Thus the objective of this study was to compare the abundance in census conducted inside fixed transects of 100 x 2 m, and surveyed at day and night of the same day. The results show that there were significantly more sea cucumbers seen during dark hours (mean ± standard error 3.714 ± 0.075) than during light time (1.943 ± 0.045 per census); daylight estimated abundance can be corrected by a linear equation (slope = 1.43; ordinate = 1.18). Therefore, the quota estimated from censuses conducted during daylight is 15% lower than those that would be obtained at night. In conclusion, daylight censuses work as a precautionary management strategy of this species.

Keywords : Precautionary fisheries management; Holothurian; Correction factor; Visual census; Species under special protection; Loreto Bay.