Two species of caligid copepods (Crustacea) parasitic on marine fishes of Venezuela,with discussion of Metacaligus Thomsen, 1949

Summary

O, I and II group flounders showed a regular increase in length and weight between April and September, but did not grow during the winter months. These immature fish showed highest condition factors and calorific values in summer and lowest in winter. III and ? IV group flounders had highest condition factors and calorific values in winter prior to spawning and lowest when they returned to the estuary as spents in April. Males matured towards the end of their third year and females towards the end of their fourth. Gonad development started in October and peak gonad weights were attained in November (males) and February to April (females).

Diurnal variations in the numbers of fish were very marked on the Sleek of Tarty where larger numbers were caught at night. Little diurnal variation was noticeable on the Forvie Bank mud flat.

Largest numbers of flounders were recorded between May and September when the population was 50–100 times larger than the winter low (January to March). Estimates of the total population size are given, based on observed densities on underwater transects.

Seasonal changes in the population of flounders on the intertidal mud flats were influenced by four major migrations:

• (1)A spring immigration (April and May) of immature (except the O group) and spent fish, the spent females being present in significantly greater numbers than males.

• (2)O group flounders entered the estuary in late June early/July, approximately two months later than the immigration of O group plaice.

• (3)A proportion of III and ? IV group flounders left the mud flats in July and tagging data suggested that they left for the sea.

• (4)The winter emigration of all age classes started in October and continued through the winter, leaving a small population composed mainly of O group and maturing fish. Cormorants preyed mainly on I and II group flounders in winter and probably accounted for the low numbers of these age groups at this time.