SUMMARY : The role of vision in the entry of the cuttlefish Sepia esculenta into basket traps was examined in laboratory experiments and by histological examination of the retina. Both entry into the trap and feeding on shore crabs stopped when the tank was completely darkened. The eyes of cuttlefish have a high sensitivity to light. The visual field of cuttlefish was determined by the optical method, based on the assumption that incident light on the pupil from any direction reaches the retina through a refractive lens. The uniocular visual field was found to be 253° on the horizontal plane, and the anterior and posterior binocular visual fields were 86° and 60° respectively. On the retina, areas with especially high visual cell density formed a visual equator slightly above the optical equator. The distribution of the visual cell density indicates no specific visual axis. The visual acuity is 0.36 when estimated from the bait recognition distance and the size of bait during feeding, and 0.89 when determined from the visual cell density at the visual equator and the focal length of the lens. Cuttlefish have far superior visual acuity than fish.
SUMMARY: The behavior of the cuttlefish Sepia esculenta near basket traps was observed in the field and in the laboratory in order to analyze the capture process of basket traps. In the field, cuttlefish spawned both during the day and the night and mainly outside the traps. This finding negates the conventional idea that the entry of cuttlefish into traps is motivated by spawning. Cuttlefish entered and exited from the trap in a straight movement with the arms first, as in feeding. No cuttlefish touched the trap during these movements, which means that the reaction of cuttlefish to traps is mediated by vision. Cuttlefish inside the trap moved very slowly, not evasively, and they remained inside for at least 2 days. This behavior indicates the existence of an attractive stimulus within the trap. In laboratory tanks, individuals repeatedly entered the trap. Because the average length of stay of six cuttlefish in the trap in the first entry (6 h 18 min) was less than in the sixth entry (8 h 19 min), exploratory behavior cannot explain the behavior of cuttlefish entering basket traps.
Artificial reefs (ARs) are one of the most popular means of supporting marine ecosystem conservation and coastal fisheries, particularly in developing countries. However, ARs generate complex socio-bio-economic interactions that require careful evaluation. This is particularly the case for ARs outside no-take zones, where fish might be subject to enhanced exploitation due to easier catchability. Here, we conducted an interdisciplinary study on how ARs impact fish and fishing yields, combining mathematical and sociological approaches. Both approaches converge to confirm that fishery yields decline when ARs are exploited as if they were open access areas. This situation typically occurs in areas with weak governance and/or high levels of illegal fishing activity, both of which are common in many developing countries. To avoid these adverse effects and their associated ecological consequences, we recommend prioritizing the onset of a long-term surveillance system against illegal fishing activities, and adapting design and location of the ARs based on both and local and academic knowledge, before the deployment of ARs.
SUMMARY: The sensory basis of the behavior of cuttlefish towards basket traps explains in part the mechanism of capture by the gear. Previous studies have shown that the reaction of cuttlefish Sepia esculenta to basket traps is mediated mainly by vision. In this study, visual factors that attract cuttlefish to basket traps were examined in the laboratory. The reaction of cuttlefish was divided into three processes of recognition, approach, and entry; the frequency and the duration of each process indicated the strength of the reaction. Cuttlefish were most attracted to a basket trap that contrasted most strongly with the background. When the dismantled components of the basket trap were presented as visual targets to cuttlefish, all the components were approached by the cuttlefish, which remained in the internal space. Cuttlefish have a habit of occupying the internal space of a structure and this habit seems to be the main motivation for entry into a trap. Another experiment was carried out to examine the social attraction between individuals inside and outside a trap. Social interference between males and females seems to be part of the mechanism of capture of cuttlefish by basket traps.
In the present study, trapping experiments and observations on the behavior of immature cuttlefish Sepia esculenta towards the traps were made under field and laboratory conditions. Trapping experi ments clearly demonstrated the entry of immature cuttlefish into the basket traps. The entry rate was sig nificantly higher in immature than in mature cuttlefish studied in the same laboratory conditions. When entering and leaving the trap, cuttlefish swam straight primarily with arms in front, thus suggesting their active movement.After entry, cuttlefish remained stationary at the bottom. Females stayed in the trap longer than 3 days, while males left within 3 days. The existence or the position of branches did not influence the entry of cuttlefish into the traps. These results may rule out the possibility that spawning is a motivation for the entry of cuttlefish into the traps.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.