Although fishers have been using DFADs for nearly a century to increase their catches, the reasons driving this associative behavior are not fully understood. The reasons of this behavior may be diverse in nature, as shown by the high number of hypotheses proposed to explain to explain why pelagic fish may associateassociated with floating objects (Castro et al., 2002). The first one, was briefly mentioned by Suyehiro (1951), and proposes that the objects act as a shelter from predatorpredators for tuna species. However, the hypothesis is unlikely for large predators such as tuna due toas tuna schools are too big to hide under small objects, which cannot be a shelter for them. Another hypothesis is that DFADs may be an indicator of food (Bard et al., 1985). This hypothesis suggests that floating objects aggregate small fish in their vicinity, on which large fish could prey. However, no strong evidence was found to support the presence of a sufficient amount of small fish near floating object is sufficientenough for tuna to sustain itself, due to tuna needneeding to eat approximately 5% of their weight each day (Olson and Boggs, 1986). Klima and Wickham (1971) proposed that floating objects could provide spatial references around which fishesfish can orient in unstructured pelagic environment, but this hypothesis is difficult to extrapolate to moving floating objects such as DFADs. Another hypothesis proposed primarily for solitary predators and then for tuna, was comfortability stipulation hypothesis . It suggests that fish remain close to floating objects to rest and recover energy after feeding in the area. However, the stomach contents of tuna are difficult to study because of the regurgitation of fish when they are caught, and the author does not explain why a tuna would choose to rest near a DFAD instead of elsewhere.

The text above was approved for publishing by the original author.

Previous       Next

무료로 시도해보기

메세지를 확인해 주세요
교정할 언어 선택

를 눌러서 워드 문서 교정하기.

eAngel.me

eAngel.me is a human proofreading service that enables you to correct your texts by live professionals in minutes.