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

Abstract

Abstract:Copepod nauplii are the primary food item for early-stage marine fish larvae, but their feeding selectivity on the nauplii of different copepod species has not been well studied. This study revealed feeding selectivity in the dominant preflexion larvae of three fishes Sebastiscus marmoratus, Sebastes sp. and Ammodytes japonicus in the Seto Inland Sea, Japan, in spring and winter. Copepod nauplii and eggs numerically constituted 80-91% of the prey items in their guts. Chesson s preference index for the nauplii of various copepod species was positive for Calanus sinicus and Paracalanus parvus sensu lato, negative for Acartia omorii, and negative or neutral for Oithona similis. This result is probably attributable to the size and swimming behavior of the prey species. The preference index in A. japonicus larvae was not significantly different between the nauplii of different species, suggesting that the larvae are less selective than the other two fishes. The preference index for Calanus eggs was very high, especially in Sebastiscus marmoratus and Sebastes sp., and most of the eggs in the guts were shrunken, probably due to digestion. In terms of volume, C. sinicus nauplii and eggs in gut contents represented 36-72% of total copepod nauplii and >80% of total copepod eggs, respectively, because of high selectivity by fish larvae and their large individual volumes compared with the dominant copepods. This indicates that C. sinicus is the most important prey species for early fish larvae despite their low abundance in the environment.

High abundances of small copepods early developmental stages and nauplii strengthen the perception of a non-dormant Arctic winter

“…Overwintering in the upper water column as copepodids in Microcalanus spp., O. similis, Pseudocalanus spp., and M. longa may be a survival strategy to reduce predation pressure. Predators, such as large copepods (Sell et al 2001;Bonnet et al 2004), chaetognaths or fish larvae (Falkenhaug 1991;Swalethorp et al 2014;Mitsuzawa et al 2017;Grønkjaer et al 2018) that prey on nauplii and small copepodids may be present in surface waters during winter, but at lower abundances than in other seasons (Daase et al 2013;Grigor et al 2014Grigor et al , 2017. Therefore, the impact of the predators' feeding activity is likely reduced, leading to lower copepod mortality.…”

Environmental characteristics of spawning and nursery grounds of Japanese sardine and mackerels in the Kuroshio and Kuroshio Extension area

“…Copepods are of great ecological importance, as they comprise one of the most abundant zooplanktonic groups and play various roles in the food web as herbivorous, omnivores/detritivores, and carnivore (Mauchline, Blaxter, Southward, & Tyler, 1998;Ohtsuka & Nishida, 1997;Sano, Maki, Nishibe, Nagata, & Nishida, 2013). The importance of two coastal/shelf-water species of copepods, Calanus sinicus and Paracalanus parvus s.l., as prey for small pelagic fish around the Kuroshio area off the coast of Japan, has been established (Hirai, Hidaka, Nagai, & Ichikawa, 2017;Mitsuzawa, Miyamoto, & Ueda, 2017;Nakata & Hidaka, 2003;Sogawa et al, 2017;Uye, 2000). Copepods are also known to prey on ichthyoplankton (Bailey & Yen, 1983;Lillelund & Lasker, 1971;Turner, Tester, & Hettler, 1985), and competition between copepods and fish larvae for food organisms has been pointed out (Ambler & Frost, 1974;Turner, Tester, & Conley, 1984;Yen, 1985).…”

Establishing an astaxanthin-rich live feed strain of Pseudodiaptomus annandalei

“…As an essential component of marine mesozooplankton, copepods substantially influence marine trophic systems. Studies investigating gut contents of several fish larvae, including silver pomfret ( Pampus argenteus ), bluefin tuna ( Thunnus thynnus ), marbled rockfish ( Sebastiscus marmoratus ), and sand lance ( Ammodytes japonicus ), underscored the significant role of copepods as natural prey items for fish larvae 2 – 4 . Copepods have been employed as live feed for aquatic larvae since the 1980s 5 , leading to enhanced aquaculture performance in larval rearing, and supporting the cultivation of many emerging marine fish species 6 – 8 .…”