Investigating the capture mechanism of scavenging gastropods in hanging-net fisheries

Abstract

ABSTRACT The current study aimed to elucidate the capture mechanism of B. brandaris and H. trunculus in two métiers of the Greek small-scale fisheries (SSF) that use trammel. The commercial and discarded catch from three commercial SSF boats was recorded in parallel to in-situ SCUBA diving observations and video analyses of the entangled catch at net retrieval. The abundance of gastropods in the nets was correlated with the abundance of captured fish in both métiers. This correlation was undoubtedly caused by the scavenging activity of gastropods on organisms captured in the lower portion of the net, such as combers, wrasses, and cuttlefish. Underwater observations revealed that the number of scavengers per fish increased gradually with the degree of fish consumption, whereas on-deck observations revealed that the foraging groups became malformed as soon as the flesh consumption was complete, as evidenced by the presence of fish bones in the absence of scavengers. Only a small percentage of the gastropods in the catch became entangled on the net, and that the majority of the gastropods were carried on deck by attaching to their entangled prey. The current study provided a clear explanation of the capture mechanism of the two muricids, as well as critical knowledge for their conservation.