Abnormal pituitary‐gonad function in two feral populations of goldfish, Carassius auvatus (L.), suffering epizootics of an ulcerative disease

Abstract

The activity of the pituitary-gonad axis was examined in goldfish, Carassius auratus (L.), collected from two popuiations exhibiting epizootics of an ulcerative disease. One population, collected from a pond in Toronto, Ontario, exhibited a significant linear relationship between the extent of lesions and the ovarian state. In a second population, collected from Hamilton Harbour, Lake Ontario, there was no correlation between the high prevalence of oocyte atresia, or the ovarian state with the extent of the ulcerative lesions. Additionally, in the Hamilton Harbour population there were no seasonal changes in the stages of egg development, frequency of mature ova, activity of the pituitary-gonad axis or gonadosomatic index consistent with gamete release. This apparent spawning failure of the Hamilton Harbour population was supported by the age distribution in the population (no fish younger than 4 years of age were found), and probably accounts for the drastic decline in the capture success of goldfish at that site since 1978. This decline in capture success was correlated with the outbreak of a persistent epizootic of ulcerative disease, suggesting that either the lesions themselves caused the spawning failure, or that the spawning failure and lesion outbreak were both eorrelated with undetermined changes in the environment, possibly a deterioration in the water quality in Hamilton Harbour.

A holistic approach to ecosystem health assessment using fish population characteristics

“…Similar changes have been reported in lake trout populations inhabiting water of pH < 5.5 (Beggs & Gunn, 1986), in a goldfish (Carassius auratus) population inhabiting a heavily polluted industrial basin (Munkittrick & Leatherland, 1984) and in a population of sauger (Stizostedion canadense) inhabiting a lake polluted by copper mining wastes (Black et al, 1985). The pattern was also found in Lake Simcoe whitefish when the mean size and age of the population increased in association with successive recruitment failures (Evans, 1978).…”

A sentinel monitoring framework for identifying fish population responses to industrial discharges

“…The absence of younger year classes in a variety of fish populationshas been associated with low pH (Beggs & Gunn, 1986), prolongedindustrial discharges (Munkittrick & Leatherland, 1984), mining wastes (Black et al, 1985) and declining water quality (Evans, 1978;Colby, 1984). The mortality of early life-stages (embryos, larvae, juvenile stages which do not share food/habitat resources with the adults) will eventually result in an metabolic disruption.…”

Population response of pale chub (Zacco platypus) exposed to wastewater effluents in Gap Stream

“…The Response of pale chub population at the downstream sites (GS 7.2 and GS 2.7) was also matched well the chronic recruitment failure, except for egg size indicator ( Table 4). The chronic recruitment failure pattern characterized by decreased recruitment that have been associated with many reasons, low pH 39 , mining wastes 40 , prolonged industrial discharges 41 and declining water quality 22,42 . In the downstream sites (GS 7.2 and GS 2.7), recruitment was impaired, and young age fish appeared in low abundance.…”