Implications of substrate complexity and kelp variability for south-central Alaskan nearshore fish communities

Understanding the interactions between kelp beds and nearshore fish is essential because anthropogenic changes and natural variability in these beds may affect available habitat for fishes. In this study fish communities were investigated in south-central Alaska kelp beds characterized by a range of substrate complexity and varying densities of both perennial understory kelps and annual canopy kelps. Many of the observed fish species, as well as understory and canopy kelps, were positively associated with structurally complex substratum. Targeted canopy and understory kelp beds supported seasonal populations of adult and juvenile Pacific cod (Gadus macrocephalus), rockfishes (Sebastes spp.), and year-round populations of greenlings (Hexagrammos spp.). Monthly changes in kelp and fish communities ref lected seasonal changes; the densities of some species were greatest during periods with higher temperatures. This work illustrates the importance of structurally complex kelp beds with persistent understory kelp populations as important fish habitat for several commercially and recreationally important fishes.

A key to selected rockfishes (Sebastes spp.) based on mitochondrial DNA restriction fragment analysis

Larval and juvenile rockfishes (Sebastes spp.) are difficult to identify using morphological characters. We developed a key based on sizes of restriction endonuclease fragments of the NADH dehydrogenase-3 and -4 (ND3/ND4) and 12S and 16S ribosomal RNA (12S/16S) mitochondrial regions. The key makes use of variation in the ND3/ND4 region. Restriction endonuclease Dde I variation can corroborate identifications, as can 12S/16S variation. The key, based on 71 species, includes most North American taxa, several Asian species, and Sebastolobus alascanus and Helicolenus hilgendorfi that are closely related to rockfishes. Fifty-eight of 71 rockfish species in our database can be distinguished unequivocally, using one to five restriction enzymes; identities of the remaining species are narrowed to small groups: 1) S. polyspinis, S. crameri, and S. ciliatus or variabilis (the two species could not be distinguished and were considered as a single species) ; 2) S. chlorostictus, S. eos, and S. rosenblatti; 3) S. entomelas and S. mystinus; 4)S. emphaeus, S. variegatus, and S. wilsoni; and 5) S. carnatus and S. chrysomelas.

Length-weight relationships of demersal fishes from the upper continental slope off Colombia

Parameters of the length–weight relationship of the form W=aLb are presented for 45 demersal fish species caught on the upper continental slope of the Caribbean Sea off Colombia. The b values varied between 2.13 and 4.97, with the mean b = 3.042 (95% CI, 2.887- 3.196).

Cholesterolgehalte in Fischereierzeugnissen vom Deutschen Markt

Kurzfassung Zahlreiche Fischereierzeugnisse aus dem Deutschen Handel wurden auf ihren Gehalt an Cholesterol hin analysiert. Zur Analyse gelangten 38 verschiedene Dauerkonserven von acht Fischarten, 4 Produkte kalt geräucherter Atlantischer Zuchtlachs in Scheiben, 10 Garnelenarten und 25 Fischstäbchenerzeugnisse von 5 Tierarten in Verbraucherpackungen. Bei den Dauerkonserven lagen die Gehalte zwischen 24 und 40 mg/100 g. Zwei Ausnahmen bildeten Sprottenkonserven mit durchschnittlich 107 mg/100 g und Oktopuskonserven mit 196 mg/100 g. Die Garnelenarten variierten zwischen 84 und 161 mg/100g. Die kalt geräucherten Lachsscheiben wiesen nur eine kleine Bandbreite im Cholesterolgehalt zwischen 38 und 43 mg/100 g auf. Alle Fischstäbchen aus Magerfischen enthielten niedrige Gehalte an Cholesterol (Pangasius hypophthalmus 25, Seehecht 19, Seelachs 31 und Alaska Seehecht 28 mg/100 g), während die zwei Proben aus Tintenfischen über 100 mg/100 g lagen. Abstract Numerous fishery products from the German market have been analysed for their content of cholesterol. In total 38 different canned fishery products produced from 8 species, 4 products of sliced cold smoked Atlantic salmon, 10 species of crustacean shellfish and 25 different brands of consumer packages of fish fingers (produced from 5 species) were investigated. Canned fishery products contained amounts of cholesterol ranging from 24 to 40 mg/100 g. However, canned sprats exhibit cholesterol content as high as 107 mg/100g and canned octopus 196 mg/100 g. Crustacean shellfish was found to contain cholesterol content between 84 and 161 mg/100 g depending of species. Sliced cold smoked salmon in 200 g consumer packages showed only a little variation in cholesterol content (38-43 mg/100 g). In all fish fingers produced from lean fish species low cholesterol content (pangasius or sutchi catfish 25, hake 19, saithe 31, and Alaska Pollack 28 mg/100 g, respectively) was found, whereas two products produced from squid exceeded 100 mg/100 g.

Effects of density-dependence and sea surface temperature on interannual variation in length-at-age of chub mackerel (Scomber japonicus) in the Kuroshio-Oyashio area during 1970–1997

Annual mean fork length (FL) of the Pacific stock of chub mackerel (Scomber japonicus) was examined for the period of 1970–97. Fork length at age 0 (6 months old) was negatively correlated with year-class strength which fluctuated between 0.2 and 14 billion in number for age-0 fish. Total stock biomass was correlated with FL at age but was not a significant factor. Sea surface temperature (SST) between 38–40°N and 141–143°E during April–June was also negatively correlated with FL at age 0. A modified von Bertalanffy growth model that incorporated the effects of population density and SST on growth was well fitted to the observed FL at ages. The relative FL at age 0 for any given year class was maintained throughout the life span. The variability in size at age in the Pacific stock of chub mackerel is largely attributable to growth during the first six months after hatching.