Influence of some physical and biological factors on the density and vertical distribution of Atlantic halibut Hippoglossus hippoglossus eggs

Abstract

Atlantic halibut Hippoglossus hippoglossus (L.) eggs were sampled using a Tucker trawl and a MOCNESS-sampler at 3 selected localities in North Norway. The specific density of the eggs was determined in a density-gradient column. The eggs were found to achieve higher specific density with increasing age. In areas with a horizontally stable, clearly defined pycnocline (Andfjord and Seraysund), the vertical distribution of eggs was characterized by a unimodal egg distribution. Furthermore, the older eggs were found at higher average capture salinities than younger eggs, i.e. they were distributed in relation to their neutral buoyancy. In an area with a horizontally more variable and less defined pycnocline (Malangen), the pattern of vertical distribution of eggs was less distinct, often with polymodal egg distributions. In this hydrographically variable system, no heterogeneity in the distribution of the various egg developmental stages could be discerned. In Malangen, thus, it is proposed that the vertical distribution of halibut eggs is most strongly influenced by physical factors.

The effects of different incubation conditions on the eggs of halibut, Hippoglossus hippoglossus (L.)

“…Eggs sampled from plankton, had neutral buoyancy at mean salinities of 33.9, 34.1 and 34.4 ppt respectively, for subsequently older stages (Haug et al, 1986), which is very similar to the values obtained in the present study.…”

Changes in egg buoyancy during development and its effects on the vertical distribution of anchovy eggs

“…Coombs (1981) introduced the density gradient column (DGC) to measure the neutral buoyancy of fish eggs. Subsequently, models for many species have been developed using the DGC (Boyra et al, 2003;Coombs et al, 1985;Haug et al, 1986;Tanaka, 1990), with some limitations linked to limited biological knowledge (Goarant et al, 2007).…”

Fine-scale spatial variability of different stages of pelagic fish eggs over the western Agulhas Bank, South Africa

“…Knowledge of the spatial distribution and abundance of ichthyoplankton in the oceans plays a central role in fisheries science (Haug et al 1986), and provides insights into the nature of fish behaviour and life-history stages, thereby enabling the design of optimal sampling protocols. Three pelagic species, anchovy Engraulis encrasicolus, sardine Sardinops sagax and round herring Etrumeus whiteheadi, are of considerable ecological and economic importance in the southern Benguela region.…”