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Size selective predation on the bivalve Macoma balthica by juvenile epibenthos

Marijnissen, S.A.E. (1998) Size selective predation on the bivalve Macoma balthica by juvenile epibenthos. Master's Thesis / Essay, Biology.

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Abstract

The tellinid bivalve Macoma baithica passes its juvenile stage in the Wadden Sea in nurseries high in the intertidal zone. The migration to and from these high tidal fiats presents various potential dangers to the animals. In order to outweigh the negative influences, the nurseries must offer major beneficial conditions to the youngest stages of M. balihica. We hypothesize that the high tidal flats are a more favorable habitat than the lower, because they offer a refi1ge from predation by juvenile epibenthos. The main epibenthic predators on Mbalihica potentially are the shore crab (Carcinus maenas), brown shrimp (Crangon crangon), plaice (Pleuronectes platessa), flounder (Platichthysflesus) and goby (Pomatoschistus sp). Stomach contents of crabs and shrimp that were caught on the high tidal flats in the eastern Dutch Wadden Sea, were analysed for shell fragments. Only very low numbers of recognizable shell fragments of M. baithica were found. On the basis of hinges found in the stomachs, the size of some consumed shells could be estimated. Size selectivity of predation on M baithica by juvenile epibenthos was estimated in an experimental situation. The data show that juvenile epibenthic predators mainly consume the smallest 0-group M baithica when a size range is offered. The electivity index E' shows that the largest size classes are significantly rejected. The fish and shrimp only consumed small amounts of bivalves. The juvenile crabs proved to be fierce predators, consuming relatively large amounts. A significant positive relationship exists between the carapace width of crabs and the mean size of bivalves they consume. Considering the impact juvenile shrimp and crabs in particulair could have on the juvenile population of M ba/thica, this may be a reason for the use of nurseries high in the intertidal zone.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:31
Last Modified: 15 Feb 2018 07:31
URI: http://fse.studenttheses.ub.rug.nl/id/eprint/9244

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