Habitat availability, reproduction and population dynamics of the fresh water Blenny Salaria fluviatilis (Asso, 1801) in lake Kinneret, israel

 

Avital Gasith, Menachem Goren

 

Department of Zoology, George S. Wise Faculty of Life Sciences, Tel-Aviv University. Tel-Aviv, 69978 Israel. avigas@post.tau.ac.il ; gorenm@post.tau.ac.il

 

Abstract: The present study investigates the relationship between water level fluctuation and population structure and dynamics of the blenny Salaria fluviatilis (Asso, 1801) (Blenniidae) in Lake Kinneret, Israel.  Except for a short pelagic phase of the larvae (ca 6 weeks), the fish spends its life in the littoral region where it feeds and breeds.

Breeding extends throughout the year and peaks from early spring (March) to mid summer (July). The blenny spawns on rocks of medium size (stone surface area of ca 500 cm2) and thus we suspect that its breeding success is affected by water level fluctuation that determines availability of rocky habitats. Highest breeding success is expected to occur when the lake level is high and rocky habitats are plentiful. The number of eggs in a nest of S. fluviatilis in Lake Kinneret varies from 500 to 8000 eggs, corresponding to 2 - 30 spawns, respectively.

The blenny shows size related habitat partition. Smaller fish are more abundant in habitats of small stones and cobbles, whereas, the larger fish are found mostly in habitats of large stones and boulders. We attribute this habitat segregation to predation avoidance behavior.

The relative importance of S. fluviatilis in the littoral zone fish assemblage (numerically and in biomass) is inversely related to water level. The blenny is the most prevalent fish in the rocky littoral in years of low lake levels, when rocky habitats are in short supply.  Diversion of water for human use increases water fluctuation of Lake Kinneret. Such action interferes with the needs of fish and other organisms that depend on rocky littoral resources. For the blenny low lake levels mean greater competition for shelters and fewer suitable spawning niches. Moreover, it limits the options of segregation between small and large blennies, forcing greater interaction between them, including cannibalism. Recent consecutive drought years, that exacerbate water shortage, forces management of Lake Kinneret under wide water level fluctuations. This in turn, reduces the fitness of S. fluviatilis.

 

Key words: Salaria fluviatilis; Blenniidae; Fish biology; Lake Kinneret; Water level fluctuation; Human impact.

 

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