HISTOLOGICAL INDEXES OF THE NUTRITIONAL CONDITION OF SARDINE, SARDINA-PILCHARDUS (WALBAUM) LARVAE OFF THE NORTH COAST OF SPAIN

Larvae of sardine (Sardina pilchardus) were sampled off the north coas t of Spain from March to June 1992 as part of a programme to investiga te factors affecting subsequent recruitment. Histological analyses of the larvae were carried out as a measure of nutritional condition for comparison with environmental variables and subsequent survival at the juvenile stage. Tissues were grouped into short-term indicators of nu tritional condition, including the digestive tract, liver and pancreas , and long-term indicators represented by cartilage, notochord and mus cle tissue. Long-term indices showed little difference between months, most specimens being in relatively good condition. Short-term indices showed greater variation because larvae sampled in March and May were in significantly poorer condition than those in April and June. A thi rd measure of condition, the presence of irreversibly damaged tissue i ndicated that larvae sampled in March were in the poorest condition. T his measure of condition was suggested as being the most objective ass essment with respect to potential larval mortality. It was not possibl e to compare larval condition with survival to the juvenile stage beca use only an insignificant number of larvae from spawning along the nor th coast of Spain recruited to the nursery area; most juveniles were d erived from spawning further to the south. It was suggested that offsh ore transport associated with upwelling off the north-west coast was r esponsible for the loss of larvae from the north coast and may be a mo re significant factor in determining recruitment than nutritional cond ition. (C) 1997 Elsevier Science B.V.