Distribution, growth, production, and ecological significance of the clam Unio terminalis in Lake Kinneret, Israel

Abstract

The distribution, body composition, growth rate, and population structure of Unio terminalis were measured at different sites of Lake Kinneret (Israel). Maximum clam density was found on the muddy sand between 0.3-6 m depth. Clams were most abundant in the River Jordan inlet zone, where they showed the highest growth rate. This was probably related to both highest food availability and the highest density of fish hosting Unio glochidia in this area. U. terminalis in Lake Kinneret has a more massive shell and ash content as compared with the European Unio species. The annual P/B ratios of U. terminalis populations at different sites were similar and ranged within 0.17-0.18. The computated filtration capacity and energetic budget permit the assumption that the U. terminalis population plays a substantial role in removal of organic particles from the water in the Kinneret shallow inshore zone (up to 15 m depth), and in nutrient recycling.

The Littoral Zone

“…terminalis on relatively steep-sloping, sandy bottom on the east side of the lake where relatively strong lateral currents prevail. Ostrovsky et al (1993) reported highest densities of Unio t. terminalis in muddy sands at 0.3-6-m depth, and especially near the Jordan River inflow. They concluded that this bivalve plays a substantial role in removing particulate matter from the water in the shallow inshore area, supplying suspended organic matter to the benthic community and regenerating nutrients.…”

Evidence of Large Change in Unionid Mussel Abundance from Selective Muskrat Predation, as Inferred by Shell Remains Left on Shore

“…Mussel densities > 10 mussels/m 2 are not uncommon OSTROVSKY et al, 1993;JOKELA and MUTIKAINEN, 1995). Even if mussels were present at much lower densities in Lake LaSalle, we still should have collected dozens of individuals during the SCUBA sampling in 1989 and grab sampling in 1993.…”

“…Freshwater mussels (Unionidae) can represent a significant portion of the benthic biomass and productivity of lakes and streams (NEGUS, 1996;OSTROVSKY et al, 1993;STRAYER et al 1981), yet their large size and durable shells probably render them impervious to most aquatic predators. The capture of unionid mussels by semi-terrestrial muskrats is not often observed directly, but the end products (empty shells) are readily collected from discrete piles at feeding sites and provide numerical evidence of the interaction.…”

Population size and structure of three mussel species (Bivalvia: Unionidae) in a northeastern German river with special regard to influences of environmental factors

“…They can reach a considerable body size and form dense populations. Due to their filtering capacities, the unionids are of great significance in the self-purification of waters (Ostrovsky et al, 1993;Ogilvie & Mitchell, 1995;Vanderploeg et al, 1995;Welker & Walz, 1998;Soto & Mena, 1999).…”