New Zealand Journal of Marine and Freshwater Research abstracts

---

Morphometric changes, gonad histology, and fecundity estimates in migrating New Zealand freshwater eels {Anguilla spp.)

P. R. TODD

Fisheries Research Division Ministry of Agriculture and Fisheries Private Bag Christchurch, New Zealand

Abstract During transition from the non-migrant feeding stage to the migrant stage in Anguilla australis and A. dieffenbachii the eyes increase in area by a factor of 2 in males and of 1.5-1.6 in females. A. dieffenbachii is more sexually advanced at the beginning of the spawning migration. In males the gonadosomatic ratio (GSR) was 0.5-2.7 and histological sections showed spermatocytes as the most common stage of spermatogenesis. For A. australis the GSR was 0.03-0.70, and histologically spermatogonia were predominant. In A. dieffenbachii females the mean GSR was 8.12, mean egg diameter was 0.33 mm, and histological sections showed that most eggs were at the stage of yolk deposition. In contrast, the mean GSR of A. australis females was 3.5, mean egg diameter was 0.22 mm, and few eggs were at the yolked stage. Egg counts showed that fecundity increased with total length. Fecundity estimates for 23 A. dieffenbachii (total length 711-1452 mm) varied from 1.05 million to 20.83 million and for 26 A. australis (total length 516-933 mm) from 0.46 million to 3.06 million.

Keywords Anguillidae; Anguilla australis; Anguilla dieffenbachii; migration; morphometric changes; gonad condition; gonadosomatic ratios; fecundity.

New Zealand Journal of Marine and Freshwater Research, 1981, Vol. 15 : 155-170 Received 8 December 1980

PDF file of entire paper: medium quality (3619K); (scanned from paper original: notes about this process)

---

This year's abstracts | Journal home page | All abstracts | Publishing home page