Aggregation based Cuttlefish fishery Geetha Sasikumar Sr. Scientist, Molluscan Fisheries Division
Cephalopods are actively sought in artisanal fisheries with highly selective gears and fishing techniques based on knowledge of their biology and behaviour (Reid et al., 2005). Such techniques use substrates for egg deposition or use live sexually mature females as lures for attracting males while targeting spawning cuttlefishes.
Benthic FADs in the form of basket traps has been the most popular cuttlefish fishing method since olden times (Watanuki and Kawamura, 1999). Basket traps were employed around Inland Sea in Japan, Atlantic coast in Europe and by countries around the Mediterranean Sea for cuttlefish. Most benthic trapping and potting is carried out in reefy areas, where fish and other animals are concentrated by the sheltered nature of the bottom, either for protection or for feeding purpose. Japanese fishermen have been using cuttlefish trap for Sepia esculenta as early as 1660’s. Full-scale trap fishery began in 1920’s, when fishermen noticed that the introduction of spawning substrates inside the traps facilitated the capture of cuttlefish. Trap fishing practices, which was popular in western Japan later spread to much wider areas including Korean Peninsula.
Though FADs can be an effective fisheries enhancement tool, there are few negative aspects in their deployment. In the current observation, the presence of only spawning individuals in FAD assemblages indicates that the cuttlefishes are attracted towards the submerged substratum for attaching the spawned eggs. In the process, the spawning individual aggregate and therefore increases their susceptibility to exploitation. Despite the fact that, fish aggregation may be highly adaptive, imparting several advantages to group members such as decreasing the risk of predation, increasing foraging efficiency and increasing reproductive success, such methods that are targeting spawners should be discouraged considering the long-term sustainability of the resource