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Evaluation of a Negative Relationship between Abundance during Spawning and Size at Maturity in Kokanee
Author(s) -
Grover Mark C.
Publication year - 2006
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/t05-188.1
Subject(s) - abundance (ecology) , population , population density , maturity (psychological) , oncorhynchus , habitat , biology , population size , density dependence , fishery , ecology , fish <actinopterygii> , demography , psychology , developmental psychology , sociology
The relationship between average size at maturity and the number of individuals present at the peak of the spawning run was evaluated in a population of kokanee Oncorhynchus nerka that experienced a large increase in accessible spawning habitat after the loss of a spawning barricade at Bucks Creek, California. Data on peak abundance, peak population density, and body sizes of spawning kokanee were compared with available data from years when the barricade restricted the spawning run. The data, which spanned a period of 34 years, collectively demonstrated that a negative size–abundance relationship caused by density‐dependent growth has been a persistent feature of the population. Peak kokanee abundance during spawning was unaffected by the presence of the spawning barricade, but peak spawning density was significantly higher during years when the spawning run was restricted by the spawning barricade than during years when the spawning run was unrestricted. The magnitude of this difference was inversely proportional to the reduction in accessible spawning habitat associated with the presence of the spawning barricade, indicating that kokanee crowded into available habitat during each spawning run and that territorial spacing did not limit peak abundances. Peak abundance increased markedly from 1999 to 2004 (the period subsequent to the loss of the spawning barricade), while size at maturity steadily declined in a manner that affected all individuals in the population. These trends indicated that (1) individual growth rates were tightly linked to population density, (2) kokanee abundance at the peak of the spawning run was related to prespawning population density, and (3) influences such as territorial spacing and temporal variation in the average age at maturity did not significantly alter or obscure the negative size–abundance relationship.