Anchovy (Engraulis encrasicolus) egg density measurements in the Bay of Biscay: evidence for the spatial variation in egg density with sea surface salinity
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Knowledge of the pelagic vertical distribution of fish eggs is central for several aspects of fisheries science including fisheries recruitment and egg production studies. In modelling egg vertical distributions, variation in fish egg density is an important issue. Though variation in egg density between individual eggs has been reported, evidence for significant spatial variation in egg density is novel. The present study provides evidence that egg density of anchovy (Engraulis encrasicolus) varies spatially across spawning sites in the Bay of Biscay, depending on the regional scale variation in sea water properties due to river discharge. We measured the density of the eggs using a density gradient column at 17 stations in 2005 and 2006 as well as their diameter. At station, the variability in the individual egg density was statistically distributed according to a Gaussian probability function. Significant variation in the mean egg density was observed across stations. Mean egg density displayed a significant correlation with sea surface salinity. Results are discussed in light of the mechanisms determining the egg density.
KeywordsSurface Salinity Oocyte Hydration Block Kriging Purse Seine Fishery Ichthyoplankton Sampling
The authors would like to thank Jacques Massé (Ifremer in Nantes) for organising the PelGas cruise in a way that allowed for the egg sampling and density measurements. Daniel Halgand (Ifremer in Nantes) contributed to the measurements on board. The study was supported by the Ifremer project FOREVAR affiliated to GLOBEC, and the European projects FISBOAT and UNCOVER.
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