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Fine‐scale vertical and horizontal movements of juvenile yellowfin tuna ( T hunnus albacares ) associated with a subsurface fish aggregating device ( FAD ) off southwestern T aiwan
Author(s) -
Weng J.S.,
Hung M.K.,
Lai C.C.,
Wu L.J.,
Lee M.A.,
Liu K.M.
Publication year - 2013
Publication title -
journal of applied ichthyology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.392
H-Index - 62
eISSN - 1439-0426
pISSN - 0175-8659
DOI - 10.1111/jai.12265
Subject(s) - yellowfin tuna , thunnus , tuna , fish measurement , fishery , diel vertical migration , oceanography , perciformes , juvenile , biology , daytime , fish <actinopterygii> , geology , ecology , atmospheric sciences
Summary An increase in yellowfin tuna ( T hunnus albacares ) catch by danish seine fisheries around the subsurface fish aggregating devices ( FADs ) in southern T aiwan waters has been a concern of local government and environmental groups. However, the attraction mechanism of aggregating tunas at the subsurface FADs is still poorly understood. The objective of this study is to examine the fine‐scale vertical and horizontal movements of juvenile yellowfin tunas around a subsurface FAD . In total, 53 tunas (35–81 cm fork length) were tagged with ultrasonic telemetry tags and released at a subsurface FAD in the waters off Shiao‐Liu‐Chiu Island, southwestern T aiwan from O ctober 2008 to D ecember 2009. These tunas stayed at the subsurface FAD for up to 31 days, with daytime vertical movement depths averaging 60–80 m at a maximum depth of 250 m. At night, the tuna gathered at a shallow depth of 40 m. The mean depth of vertical movement in the daytime is significantly different from that of the nighttime (P < 0.05). The maximum detectable distance of horizontal movement was 1.6 km, with 80% of the long horizontal movements occurring in the daytime. It is likely that the purpose of these vertical and horizontal movements was for feeding or avoiding predators. Moreover, the tagged tunas did not depart from the subsurface FAD simultaneously, suggesting distinct behaviors in their movements.