Age and growth of largemouth bass at Freshwater Lagoon, Humboldt County, California

Pagliughi, Stephen

Taken directly from abstract; "The quality of the largemouth bass fishery at Freshwater Lagoon was evaluated by assessing age structure, stock structure, condition, and growth characteristics. A total of 1,511 largemouth bass was sampled from 1986 through 2000 using a boat electroshocker. Scales were collected from 706 fish and assigned ages. Eleven age classes ere identified with a maximum age of 10 years. Age assignment precision between two readings was 95%. Paired scale and otolith samples were collected via hook-and-line from 20 largemouth bass in spring and early summer of 2002. The agreement rate of age determination between structures was used as a means of validating the utility of using scales for ageing largemouth bass. The between structure agreement rate was 75%. Scales were found to be a precise and accurate method for estimating age and growth parameters up to age 5. Sectioned otoliths were superior to scales in determining age and growth parameters up to age 5. Sectioned otoliths were superior to scales in determining age through all cohorts. From 1987-2000, the population shifted from a greater percentage of older fish to a greater percentage of younger fish. Stock structure assessment using the Relative Stock Density (RSD) index indicated the fishery at the lagoon is of high quality with good numbers of large fish present. However, the lagoon does not produce trophy class fish. Combined results from age and stock structure analyses revealed a well-balanced and stable population and desirable recruitment and mortality level through all cohorts. The number of old fish peaked in 1993. Fulton's condition factor (K) was used to assess fish condition. Mean K values at age for Freshwater Lagoon were higher than or equal to those reported at Lake Barryessa, California except for fish aged 0 and 2. The mean K value for all samples combined was higher than those reported for 48 of 50 systems from across the United States. The growth characteristics of largemouth bass from Freshwater Lagoon were generally poor compared to other systems. However, the rate of growth for age 2 and 3 fish was exceptional. The results from this study indicate that cool climate on the Northcoast of California is capable of producing and sustaining high quality largemouth bass fisheries. The fishery at Freshwater Lagoon should be closely monitored to maintain its high quality."

Age and growth of largemouth bass at Freshwater Lagoon, Humboldt County, California

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