Diel patterns of vertical distribution in larvae of southern bluefin Thunnus maccoyii, and other tuna in the East Indian Ocean

Abstract

Vertical distributions of larvae of 3 tuna species were investigated in the East Indian Ocean. In the presence of a strong pycnocline, the entire depth range of tuna larvae could be covered by sampling the mixed layer by both day and night. A small proportion of tuna larvae were found below the mixed layer when the pycnocline was weak. Thunnus maccoyii and T. alalunga larvae moved into the surface layers durlng the day. Katsuwonuspelamis, however, moved into deeper water during the day. All species of tuna were more evenly dispersed in the mixed layer at night. Greater numbers and larger larvae of T rnaccoyli and K pelanijs were captured at night, indicating marked differences in net avoidance between day and night. No evldence of increased avoidance during the day was found in T alalunga. The relative abundance of T m a c c o j~~i larvae could be predicted from surface tows; however, the relationship between surface and obllque tows showed regional and diel variability. To reduce blas and increase preclslon, estimates of tuna larvae abundance should be based on oblique tows made at night from the surface to just below the mixed layer.

A comparison of sampling methods for larvae of medium and large epipelagic fish species during spring SEAMAP ichthyoplankton surveys in the Gulf of Mexico

“…Scombrid larvae exhibited different vertical distributions by species as has been described in previous studies (Davis et al 1990;Boehlert and Mundy 1994;Hare et al 2001). The greatest abundances for T. thynnus, K. pelamis, and other Thunnus spp.…”

“…In contrast to K. pelamis and other Thunnus taxa, T. thynnus exhibited more compressed vertical and horizontal distributions in the Gulf of Mexico. These differences may be a result of a shallower thermocline, halocline, or pycnocline (Davis et al 1990;Hare et al 2001) as would be seen in divergences associated with boundaries of anti-cyclonic eddies and the loop current frontal zone.…”

“…Many of these taxa have shown vertical and horizontal distributions (Davis et al 1990;Boehlert and Mundy 1994;Hare et al 2001;Prince et al 2005;Richardson et al 2009;Muhling et al 2010;Lindo-Atichati et al 2012;Rooker et al 2012) that would suggest direct or indirect competition with bluefin tuna larvae. Thus, it is necessary to obtain accurate data regarding their distributions, which will depend highly on the sampling effectiveness of the particular gear used in surveys.…”

Fish larvae retention linked to abrupt bathymetry at Mejillones Bay (northern Chile) during coastal upwelling events

“…The vertical distribution of fish larvae has often been linked to the thermal stratification of the water column (Roepke et al, 1993;Boehlert & Mundy, 1994;Moser & Pommeranz, 1999). The thermocline is considered important as a barrier (Smith & Suthers, 1999) or as an indirect measurement of the offshore Ekman layer, that acts above or below in the vertical distribution of some fish larvae (Coombs et al, 1981;Davis et al, 1990;Olla & Davis, 1990;Rojas, 2014). The significant correlations found between the depth values of physical variables with the vertical position of some fish larvae having bathy-mesopelagic (V. lucetia) and epimesopelagic (T. oculeus) habits, suggest that location of the thermocline and oxygen minimum zone may have a large influence on the vertical distribution of these species.…”

Diel vertical migration related to foraging success in snapper Chrysophrys auratus larvae

“…433: 185-194, 2011 the day (e.g. Brewer & Kleppel 1986, Davis et al 1990, Jenkins et al 1998. Diel vertical migratory behaviour can vary taxonomically, with nocturnal ascent being the most commonly observed pattern for marine fish larvae (Neilson & Perry 1990).…”