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Relationship of Gonadal Development to Body Size and Plasma Sex Hormone Concentrations in Female Channel Catfish
Author(s) -
Davis Kenneth B.,
Simco Bill A.,
Silverstein Jeffrey T.
Publication year - 2005
Publication title -
north american journal of aquaculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 41
eISSN - 1548-8454
pISSN - 1522-2055
DOI - 10.1577/a04-066.1
Subject(s) - spawn (biology) , catfish , biology , ictalurus , gonadosomatic index , estrogen , endocrinology , population , medicine , hormone , body weight , testosterone (patch) , zoology , fishery , fish <actinopterygii> , fecundity , demography , sociology
Most channel catfish Ictalurus punctatus do not spawn until age 3, which makes the process of genetic selection for desired characteristics time consuming. A simple method for identifying earlier‐maturing fish would speed up the selection process. Two‐ and three‐year‐old females (U.S. Department of Agriculture [USDA]‐103 strain) were used to correlate body weight and plasma sex hormone concentrations with gonadal development. We also examined the potential of reducing the time to maturation with exogenous estrogen. The USDA‐103 females are known to spawn at age 2 in a higher percentage than other strains. The body weight of 2‐year‐old USDA‐103 females ranged from 436 to 884 g, and the gonadosomatic index (GSI) ranged from 0.34% to 6.64%. A population of 2‐year‐old USDA‐103 fish that had been hormonally sex‐reversed to females (SR103) weighed from 400 to 1,400 g and had GSIs ranging from 1% to 10%. Three‐year‐old SR103 females weighed from 1,300 to 2,800 g and had GSIs ranging from 2% to 14%. Only about 10% of the 2‐year‐old SR103 females had GSI values similar to the expected level for fish ready to spawn. Plasma estrogen concentration was a more reliable predictor of GSI than was body weight. Body size was significantly correlated with GSI in 2‐year‐old USDA‐103 and SR103 females but not in 3‐year‐old SR103 fish; plasma estrogen was highly correlated with GSI in fish of both ages. Plasma estrogen, testosterone, and GSI were markedly lower in 2‐year‐old fish than in 3‐year‐old fish in both populations of USDA females. Oral administration of estrogen to 2‐year‐old USDA‐103 females increased plasma estrogen but did not increase ovarian development.