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

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.

KEYWORDS:

• small-scale fisheries
• trammel nets
• muricids
• discards
• Mediterranean

Acknowledgments

The current study was carried out as part of the ‘ENVIRO_NETS: mitigating the environmental impact of trammel nets’ project, which was funded by the Greek Operational Programme for Fisheries and Sea (2014–2020), under the call for ‘innovation related to the conservation of marine living resources’ [MIS 5068822]. The authors would like to thank Chryssanthi Antoniadou and Katerina Charitonidou for their assistance with laboratory analysis and scientific diving and Maria Garagouni for curating the database. Konstantina Vei and Dimitris Pavlidis are thanked for their assistance at experimental fishing trials. A special thanks goes to the collaborating fishers for sharing their knowledge and insights throughout all stages of this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Greek Operational Programme for Fisheries and Sea (2014-2020),: [Grant Number MIS 5068822].