Date of Award

Spring 1993

Project Type

Dissertation

Program or Major

Zoology

Degree Name

Doctor of Philosophy

First Advisor

Peter F Sale

Abstract

Using field experiments and descriptive analyses this study investigated the significance of larval settlement and post-settlement processes to populations of cunner, Tautogolabrus adspersus. At small spatial scales there was no relationship between the density of new recruits and the percent cover of kelp, foliose algae and branching algae. Crustaceans and mussels were preferred found items of juvenile cunner, and significantly greater numbers of isopods, amphipods and newly settled mussels were present in patches where fish were present than in randomly selected patches.

Experimental and correlative analyses demonstrated that variation in recruitment could not be explained by the presence of conspecifics. Manipulations of macroalgal structure showed that the distribution of fish was influenced by the algal habitat. The dispersion of macroalgae influenced the demography of cunner. Settlement was greater to randomly placed than to clumped habitats; however, no differences in recruitment between random and clumped habitat were detected. The magnitude of the change in recruit number between sampling dates did not differ between clumped and random habitats. There was no evidence of either density-dependent mortality or settlement.

A larger scale study was conducted comparing the demography of cunner in Newfoundland and the Gulf of Maine. Greater numbers of adult fish were observed in Newfoundland, but higher numbers of juveniles and recruits were found in the Gulf of Maine. In the Gulf of Maine variation was pronounced at the site scale, while in Newfoundland variation was pronounced at both the site and location scales. Variation in recruitment was not expressed as subsequent variation in older age classes. There was no effect of topographic complexity on variation of densities of recruits or juveniles, but in Newfoundland a negative relationship between adults and topography was observed. Algal cover was not important in Newfoundland, but was important in the Gulf of Maine. Although there was consistently greater than 2 orders of magnitude difference in densities of pre-settlement fish between two locations, the location that received fewer pre-settlement fish actually had higher recruitment.

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