Reproductive biology of the icefish Champsocephalus esox (Günther, 1861) (Channichthyidae)

Abstract

Champsocephalus esox is the only icefish species found outside Antarctica. In a population from the Beagle Channel, the complete annual reproductive cycle has been determined. Gonad maturity stages have been established for males and females by histological analysis. Males are sexually mature from January–September with a maximum gonadosomatic index (GSI) of 3.63%. Histologically, testes are very homogeneous and the degree of maturation of the testicular cysts is similar among different tubules at the same maturation stage. Running ripe testes have mature sperm and a few spermatogoniae arranged near the blind end of the tubules. In sexually active females that are found from February–November, ovaries contain only ripe oocytes or postovulatory follicles, together with a batch of previtellogenic oocytes. During hydration, oocyte diameter reaches 2.7 mm, and oocyte dry weight increases due to material intake, the maximum GSI in ovulated ovaries is 21.89 and hepatosomatic index (HSI) decreases. These facts suggest a transfer of matter from liver to the gonads. Absolute fecundity ranges from 3303–8600 oocytes. Relative fecundity ranges from 22.5–43.5 oocytes per gram total weight. In C. esox, relative fecundity has a similar range to those quoted for the different C. gunnari populations, whilst mature oocyte diameter is small and reproductive season extended compared to the same parameters in other Channichthyidae.

Maturity and fecundity of Champsocephalus gunnari , Chaenocephalus aceratus and Pseudochaenichthys georgianus in South Georgia and Shag Rocks Islands

“…Previous reports indicate that egg diameter varies from 2.7 mm in C. esox (Calvo et al, 1999) to 3.2e3.7 in C. gunnari (Kock, 1981;Duhamel, 1991). In this study C. gunnari hydrated oocyte diameter was between 1.22 and 2.5 mm with an average of 1.65 mm (CI 95% ¼ 0.05) and had a significant positive relationship to female size and weight (P < 0.0001; Fig.…”

Somatic energy content and histological analysis of the gonads in Antarctic fish from the Scotia Arc

“…Reproductive characteristics were studied only in H. antarcticus (Daniels, 1978;White and Burren, 1992). The genus Champsocephalus has the nonAntarctic species C. esox, confined to the Magellan Province, whose reproductive biology was studied in a population inhabiting the Beagle Channel (Calvo et al, 1999). Sexually mature males are found from January to September, and females containing 3300 to 8600 mature oocytes or POF are found from February to November.…”

Reproductive strategy of a primitive temperate notothenioid Eleginops maclovinus

“…The ovary development during maturation in E. maclovinus has its highest potential fecundity occurring at stage III, and there is a gradual decrease until final fecundity, which is formed at late stage IV. The latter pattern is very similar to that observed in other polycyclic intermittent freshwater and marine spawners (Ivankov, 1985; Calvo et al ., 1999). The fecundity estimates exceeded that of Gozstonyi (1980) by an order of magnitude, because the only female he investigated was small, 40 cm L T , as opposed to 67–78 cm L T in the present study.…”