ISSN:
1573-5117
Keywords:
growth
;
stock assessment
;
inflow-rotifer-recruitment relationship
;
zooplankton consumption
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Catch analyses indicate increases in Mirogrex standing stock (exploited phase) from 〈 2000 tonnes in the early 1950's to 〉 12000 tonnes in the mid-1980's and a declining abundance after 1986. Brood strength is related to concentrations of influxed organic matter which provide larval food. Estimated von Bertalanffy growth parameters (L ∞ = 164 mm TL, K = 0.25 per yr for males; L ∞ = 198 mm, K = 0.14 for females) denote a low production/biomass ratio compared to temperate cyprinid populations, and a low rate of food consumption. From estimates of zooplankton production in recent years, an average predation of 〈 3 % fish weight/day is calculated. The decline in zooplankton biomass since 1970 is attributed to overgrazing by Mirogrex at high stock levels. At a lower biomass, the fish population can promote ecosystem stability. Mortality estimates from Mirogrex size distribution in a period of low exploitation were ∼ 1.5 times K-values for both males and females. Similar M/K ratios were estimated for two unexploited cyprinid stocks (Phoxinus phoxinus and Acanthobrama lissneri).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00006413
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