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The importance of Colorado River flow to nursery habitats of the Gulf corvina (Cynoscion othonopterus)

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Abstract:

We test the hypothesis that Colorado River flow is important in providing nursery habitat for the Gulf corvina (Cynoscion othonopterus), a commercially valuable and endemic fish in the upper Gulf of California. We use oxygen isotopes in otoliths to determine when these fish inhabit isotopically different bodies of water (Gulf of California versus the Colorado Estuary). The 18O values in the natal otoliths of C. othonopterus, significantly more negative than can be predicted by temperature alone, provide evidence that this species uses the brackish habitats created by flow of the Colorado River. A significant log-linear relationship between the natal 18O values and the cumulative flow of the Colorado River during natal development confirms use of brackish habitat in years that the Colorado River water reached the Gulf. Natal 18O values indicate that C. othonopterus seek out estuarine habitats with salinities between 26‰ and 38‰. Reduction in Colorado River flow since the construction of upstream dams has reduced the size of nursery habitat for C. othonopterus. Our results support the hypothesis that declines in commercial landings can be at least partially attributed to reduced river flow. Increased flow would increase nursery habitat and likely benefit recruitment.

Nous évaluons l'hypothèse selon laquelle le débit du Colorado joue un rôle important dans l'établissement de l'habitat de nursery pour l'acoupa du golfe (Cynoscion othonopterus), un poisson endémique d'importance commerciale dans la partie supérieure du golfe de Californie. L'analyse des isotopes d'oxygène dans les otolithes nous permet de déterminer si ces poissons habitent le golfe de Californie ou l'estuaire du Colorado, des eaux distinctes par leurs isotopes. Les valeurs significativement plus négatives de 18O des otolithes de naissance de C. othonopterus qu'on ne peut expliquer par la seule température sont des preuves que cette espèce utilise les eaux saumâtres crées par le débit du Colorado. Il existe une relation logarithmique linéaire entre les valeurs natales de 18O et le débit cumulé du Colorado durant le développement natal, ce qui confirme l'utilisation des eaux saumâtres les années où l'eau du Colorado atteint le golfe. Les valeurs natales de 18O indiquent que C. othonopterus recherche les habitats estuariens à salinité comprise entre 26 ‰ et 38 ‰. La réduction du débit du Colorado depuis la construction de barrages en amont a rétréci la taille de l'habitat de nursery de C. othonopterus. Nos résultats appuient l'hypothèse qui veut que les diminutions des débarquements commerciaux soient en partie attribuables au débit réduit du fleuve. Une augmentation du débit accroîtrait l'habitat de nursery et améliorait vraisemblablement le recrutement.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: December 1, 2005

More about this publication?
  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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