Spatial distribution and feeding habits of Pacific cod (Gadus macrocephalus) larvae in Mutsu Bay, Japan

Abstract

The spatial distributions and feeding habits of Pacific cod (Gadus macrocephalus) larvae, and the spatial distributions of copepod nauplii and copepodites, their main prey, were examined in Mutsu Bay from February to March during 1989–92. Yolk‐sac larvae were caught at 30–45 m depth at the bay mouth. Larvae without yolk were collected at 8–45 m depth at the bay mouth and the inner part of the bay, and large larvae were chiefly found in the bay. This geographical pattern in larval size may have been because of transport to the inner part of Mutsu Bay by the Tsugaru Warm Current. The dominant taxa of copepod nauplii and copepodites in the diet and the environment changed each year. Larvae fed mainly on abundant taxa in the environment, suggesting that larvae are opportunistic feeders. Nauplii and copepodites were abundant in the bay, especially in 1992. Copepodites were slightly more abundant in the diet of cod larvae in 1992 than in 1991, but this difference was smaller than in the environment. In addition, larvae with empty digestive tracts were scarce in 1991 and 1992. Prey concentrations in the bay in 1991 and 1992 seem to have been high enough to sustain most Pacific cod larvae.

Feeding selectivity of early-stage fish larvae on the nauplii and eggs of different copepod species

“…nauplii and Paracalanus-type nauplii with the composition of copepod nauplii in the diets closely matching that in the plankton assemblage (Hirakawa et al 1997). A similar opportunistic feeding pattern was observed for larvae of the Pacific cod Gadus macrocephalus Tilesius, 1810 in Mutsu Bay, northern Japan (Takatsu et al 2002), in which the larvae fed mostly on the dominant taxa of copepod nauplii in the environment.…”

“…Copepods constitute a major prey resource for various marine fish larvae, of which the survival and recruitment have been the focus of studies on commercial fish species in relation to the spatiotemporal heterogeneity of copepod abundance (Kane 1984, Peterson & Ausubel 1984, Hirakawa et al 1997, Takatsu et al 2002. Studies that successfully identified copepods to the species level have shown that fish larvae feed selectively on different copepod species and that the selectivity depends on fish species and fish size (Checkley 1982, Kane 1984, Govoni et al 1986, Hansson et al 1990, Van Ginderdeuren et al 2014.…”

Experimental evidence of fatty acid limited growth and survival in Pacific cod larvae

“…For these reasons rotifers still represent the best vehicle to experimentally examine the effects of prey quality on fish larvae. Larvae of Pacific and Atlantic cod feed opportunistically on protozoa, copepod nauplii or copepodites in the wild (van der Meeren & Naess 1993, Takatsu et al 2002). Takatsu et al (2002) showed that Pacific cod larvae off Japan consumed a variety of copepod nauplii and copepodites.…”

“…Larvae of Pacific and Atlantic cod feed opportunistically on protozoa, copepod nauplii or copepodites in the wild (van der Meeren & Naess 1993, Takatsu et al 2002). Takatsu et al (2002) showed that Pacific cod larvae off Japan consumed a variety of copepod nauplii and copepodites. Over a 3 year study, small larvae (3.6 to 7.0 mm TL) had many nauplii (41 to 83% of prey items) while large larvae (7.1 to 15.5 mm TL) had mostly copepodites (80.4 to 99.5%) in their guts.…”

Estimating the Abundance and Fishing Mortality of Pacific Cod Gadus macrocephalus during the Spawning Season in Jinhae Bay, Korea, Using a Mark-Recapture Method

“…3) , 1990;Dunn and Matarese, 1987;Poltev, 2007;Savin, 2007;Savin, 2008;Shimada and Kimura, 1994;Takatsu et al, 2002 …”