Diel vertical distribution of fish larvae during the winter-mixing period in the Northwestern Mediterranean

Abstract

A. SabatésSabatés, A. Diel vertical distribution of fish larvae during the winter-mixing period in the Northwestern Mediterranean. e ICES Journal of Marine Science, 61: 1243e1252.The vertical distributions of the larvae of shelf and oceanic fish species that spawn during the winter-mixing period in the Mediterranean are described from 22 vertically stratified plankton tows. Diel differences in the vertical distribution patterns in relation to physical data and potential prey abundance throughout the water column were examined. Even in absence of stratification, the larvae of the various fish species showed different patterns of vertical distribution and diel changes. The larvae of shelf-dwelling species were found in the surface layers, mainly above 50-m depth, and with some exceptions, with very little diel variation in depth distribution. Therefore, the vertical distribution of the larvae of these species coincided with the maximum concentrations of their potential food, nauplii and copepodite stages of copepods. The larvae of mesopelagic fishes showed deeper distributions in the water column and most of these species were located closer to the surface during the day than at night. Given the homogeneity of the physical characteristics throughout the water column, except for light, this behaviour may be determined not only by the higher concentration of prey in the surface layers but also by adequate light levels for feeding.

Larval development and growth of the European hake <i>Merluccius merluccius</i> in the northwestern Mediterranean

“…The lack of significant differences between growth rates in length estimated for the three cruises was probably related to the vertical distribution of hake larvae, mainly below 50 m (Coombs and Mitchell, 1982;Sabatés, 2004). Due to the thermal characteristics of the hake spawning areas studied, with values ranging from 13 to 15ºC at this depth, we conclude that hake larvae develop under similar temperatures independently of the time of the year.…”

Environmental influences on the recruitment process inferred from otolith stable isotopes in Merluccius merluccius off the Balearic Islands

“…This pattern of ontogenetic variation in otolith δ 13 C is common to other species and results from predation at higher trophic levels being more enriched in 13 C (see references above). We might expect an enrichment in 13 C in the otoliths of larger hakes (> 30 cm) when their diet is totally composed of fish as observed in other demersal species (Gao et al 2001, 2004, Jamieson et al 2004). …”

“…The distribution of hake larvae is probably associated with the layers of maximum productivity (deep chlorophyll and zooplankton maxima) during the seasonal water column stratification (Olivar et al 2003), whilst there are no vertical gradients during seasons with vertical mixing, when hake might make higher vertical diel displacements in search of their prey (Olivar et al 2003, Sabatés 2004. During the night, large numbers of hake larvae gather at 60 to 80 m depth, while during the day vertical distribution can extend up to 10 m from the surface (Sabatés 2004). The temperature estimates from the otolith edge for fish caught in SO were systematically higher than for fish caught in CA, and these significant differences stand irrespective of the error of measurement (between 1.1 and 1.3°C; Høie et al 2004b).…”

Larval fish assemblages off central Chile upwelling ecosystem

“…For example, Sánchez-Velasco et al (2006) described that cyclonic circulation inside a shallow bay was linked to the spatial distribution of a coastal assemblage that spread out in the same area of circulation. Presence of more stable water column, wind induced mixing and the depth and the strength of the thermocline may also influence the abundance and vertical distribution of larval fish assemblages (Gray & Kingsford 2003, Sabatés 2004, Sánchez-Velasco et al 2007. Also, even in very nearshore areas, larval fish assemblages seem to be vertically structured at a small scale (a few meters) (Borges et al 2007a).…”