Abstract
Mortality during the early stages is a major cause of the natural variations in the size and recruitment strength of marine fish populations. In this study, the relation between the size-at-hatch and early survival was assessed using laboratory experiments and on field-caught larvae of the European sardine (Sardina pilchardus). Larval size-at-hatch was not related to the egg size but was significantly, positively related to the diameter of the otolith-at-hatch. Otolith diameter-at-hatch was also significantly correlated with survival-at-age in fed and unfed larvae in the laboratory. For sardine larvae collected in the Bay of Biscay during the spring of 2008, otolith radius-at-hatch was also significantly related to viability. Larval mortality has frequently been related to adverse environmental conditions and intrinsic factors affecting feeding ability and vulnerability to predators. Our study offers evidence indicating that a significant portion of fish mortality occurs during the endogenous (yolk) and mixed (yolk /prey) feeding period in the absence of predators, revealing that marine fish with high fecundity, such as small pelagics, can spawn a relatively large amount of eggs resulting in small larvae with no chances to survive. Our findings help to better understand the mass mortalities occurring at early stages of marine fish.
Highlights
Capabilities than smaller ones, and ii) fast-growing larvae experience a shorter duration of the larval period, decreasing the period of time when they are most vulnerable to predators
There is a fair amount of field and laboratory research showing that the mortality of fish larvae is growth-dependent (e.g.6–8), most previous studies have focused on how extrinsic factors such as adverse environmental conditions impact survival by reducing larval growth
Our study provides solid evidence that the survival probability of fish larvae, both for larvae reared in the laboratory and for wild specimens, is closely linked to the size of the larvae at hatch
Summary
Capabilities than smaller ones, and ii) fast-growing larvae experience a shorter duration of the larval period, decreasing the period of time when they are most vulnerable to predators. There is a fair amount of field and laboratory research showing that the mortality of fish larvae is growth-dependent (e.g.6–8), most previous studies have focused on how extrinsic factors such as adverse environmental conditions impact survival by reducing larval growth (size-at-age). The main objective of this work was to assess the relation between size-at-hatch and early viability of the larvae of European sardine Our analysis included both wild individuals collected from the field and sardine larvae reared in the laboratory under different feeding conditions. Unveiling the relationship between size-at-hatch and survival potential in the laboratory and field will help clarify whether this intrinsic factor plays a direct role in the mortality experienced by sardine larvae and the potential for year-class success
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