Seasonal abundance and depth distribution ofBlennius fluviatilisand introducedLepomis gibbosus, in Lake Banyoles (Catalonia, Spain)

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Abstract

Temporal and spatial occurrence of limnetic larval fish in Lake Banyoles in the spring and summer of 1993 and 1994 indicated that pumpkinseed spawned over 15 weeks (from mid-May to mid-August) and freshwater blenny over 14 weeks (from mid-May until early August). We noted that the spawning period of pumpkinseed commenced earlier in Lake Banyoles than in more northern lakes.

Pumpkinseed and freshwater blenny larvae were collected by tow net in both the limnetic (at 4-4.5 m) and littoral zones (at 0-0.5 m), during daylight (no samples were taken during night). Freshwater blenny larvae were more abundant than pumpkinseed larvae. Both of them were more abundant in 1993 than in 1994 (pumpkinseed: 1.61 ind. 100 m-3 vs. 0.70 ind. 100 m-3; freshwater blenny: 3.95 ind. 100 m-3 vs. 1.90 ind. 100 m-3) and in both years they were uniformly distributed in the lake, without differences between the areas considered. The pumpkinseed larvae migrated at 3.5 mm TL into the limnetic zone, and returned to the vegetation of the littoral zone as juveniles. The freshwater blenny larvae were also planktonic (3.5-14 mm TL) but were distributed in both the littoral and limnetic zone before benthic settlement. The larval distribution is discussed on the basis of a trade-off between foraging and predation risk.

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