Growth and survival of sockeye salmon (Oncorhynchus nerka) from Karluk Lake and River, Alaska, in relation to climatic and oceanic regimes and indices, 1922–2000

We examined whether the relationship between climate and salmon production was linked through the effect of climate on the growth of sockeye salmon (Oncorhynchus nerka) at sea. Smolt length and juvenile, immature, and maturing growth rates were estimated from increments on scales of adult sockeye salmon that returned to the Karluk River and Lake system on Kodiak Island, Alaska, over 77 years, 1924–2000. Survival was higher during the warm climate regimes and lower during the cool regime. Growth was not correlated with survival, as estimated from the residuals of the Ricker stock-recruitment model. Juvenile growth was correlated with an atmospheric forcing index and immature growth was correlated with the amount of coastal precipitation, but the magnitude of winter and spring coastal downwelling in the Gulf of Alaska and the Pacific Northwest atmospheric patterns that influence the directional bifurcation of the Pacific Current were not related to the growth of Karluk sockeye salmon. However, indices of sea surface temperature, coastal precipitation, and atmospheric circulation in the eastern North Pacific were correlated with the survival of Karluk sockeye salmon. Winter and spring precipitation and atmospheric circulation are possible processes linking survival to climate variation in Karluk sockeye salmon.

Plerchis heterorchis N. sp. (Digenea: Acanthocolpidae Luhe, 1909) from fishes Lutjanus johnii and Otolithus argenteus of Karachi coast, Pakistan

A new species of trematodes Pleorchis heterorchis is described from the fishes Lutjanus johnii and Otolithus argenteus of Karachi coast. The new species is characterized by having a lanceolate body with a notch at the middle of the posterior end of the body. Body surface is smooth, ventral sucker rounded, situated at the anterior middle region of the body, pre-pharynx is well developed, widened posteriorly, pharynx muscular, oesophagus short, intestine H-shaped with anterior arms much shorter than the posterior, intestinal bifurcation almost in the middle of fore body, anterior caeca wide and short extending as far as anterior limit of pharynx. Posteriorly caeca reach to posterior end of the body with no lateral out pocketing. Testes 44 in number, intercecal arranged in 2 parallel rows, sub-globular, entire to slightly irregular, almost of same sizes extending immediately from posterior of the ovary to anterior of excretory vesicle. Cirrus pouch overlaps the ventral sucker, extends into hind body, terminating above the ovary, containing bipartite seminal vesicle, pars prostatica and ejaculatory duct. Genital pore behind the intestinal bifurcation and pre-acetabular. Ovary pre-testicular, consists of 16 follicles of varying sizes. Vitellaria lateral, follicular, extending from post bifurcal to posterior extremity. Excretory vesicle reaches to the posterior level of last pair of testes.