Geographic differences in recruitment and population structure of a temperate reef fish

Levin, Phillip S. and Chiasson, Wayne and Green, John M. (1997) Geographic differences in recruitment and population structure of a temperate reef fish. Marine Ecology Progress Series, 161. pp. 23-35. ISSN 1616-1599

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Abstract

The purpose of this study was to assess the importance of pre- and post-settlement processes in the temperate reef fish Tautogolabrus adspersus at multiple spatial scales and in 2 distinct regions, Newfoundland, Canada, and the Gulf of Maine, USA. We examined a total of 20 sites (separated by 100 to 1000 m) nested within 10 locations (separated by ca 10 km). Greater numbers of adult fish were observed in Newfoundland than in the Gulf of Maine; however, higher abundances of newly recruited fish occurred in the Gulf of Maine. An experiment in which we provided standardized habitats in both regions also revealed that recruitment was higher in the Gulf of Maine than Newfoundland. In the Gulf of Maine, variation in the densities of adults and newly recruited fish was most pronounced among sites, but in Newfoundland we detected pronounced variability at both the site and location scales. Algal height was not associated with among-site variability in the abundances of recruits or adults. Algal coverage, however, was an important predictor of variability of fish abundance in the Gulf of Maine but not in Newfoundland. The age structure of Newfoundland populations suggests that strong recruitment years are rare, while in the Gulf of Maine the age structure is consistent with the expectation of declining abundance with age. Our data suggest that pre-settlement processes are not of primary importance to cunner populations in the Gulf of Maine. Rather, we hypothesize that habitat-related differences in post-settlement processes are the most significant factors affecting these populations. However, in Newfoundland the evidence gathered thus far supports the hypothesis that episodic settlement is responsible for much of the variation in population size in this region.

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