We provide evidence that in male Atlantic salmon (Salmo salar) parr, maturation is suppressed when mesenteric fat fails to exceed an undefined level by May. In nonmaturing parr the postwinter increase in total lipids began in May, while the mesenteric store started filling in June. However, in male parr which would have matured, total lipids started increasing a month earlier, in April, and the mesenteric store started filling in May. Consequently, maturing male parr had significantly more mesenteric fat than nonmaturing fish by June. Mesenteric fat is needed for maturation. Levels continued to increase in nonmaturing parr during autumn months, but had declined in maturing parr by September. This depletion of mesenteric fat in maturing males coincided with increases in the gonadosomatic index from 0.05 to 10% and with reductions in both feeding and growth. Fasting during spring months delayed increases in total lipids and fat accumulation into the mesenteric store until June and suppressed maturation rates of male parr. The internal decision to suppress maturation is therefore dependent on mesenteric fat levels increasing in May. However, this requires the prior replenishment of other stores in April. A model is proposed to explain the physiological link between fat accumulation during spring and the initiation of maturation.

1. Duplicate groups of rainbow trout (Salrno gairdnerz] (mean weight 11 g) were given for 40 weeks one of four partially purified diets that were either adequate or low in selenium or vitamin E or both.2. Weight gains of trout given the dually deficient diet were significantly lower than those of trout given a complete diet or a diet deficient in Se. No mortalities occurred and the only pathology seen was exudative diathesis in the dually deficient trout.3. There was significant interaction between the two nutrients both with respect to packed cell volume and to malondialdehyde formation in the in vitro NADPH-dependent microsomal lipid peroxidation system. 4. Tissue levels of vitamin E and Se decreased to very low levels in trout given diets lacking these nutrients. For plasma there was a significant effect of dietary vitamin E on Se concentration.5. Glutathione (GSH) peroxidase (EC 1 . 1 1 . 1 .9) activity in liver and plasma was significantly lower in trout receiving low dietary Se but was independent of vitamin E intake. The ratios of hepatic GSH peroxidase activity measured with cumene hydroperoxide and hydrogen peroxide were the same for all treatments. This confirms the absence of a Se-independent GSH peroxidase activity in trout liver.6. Se deficiency did not lead to any compensatory increase in hepatic GSH transferase (EC 2 . 5 . 1 . 18) activity; values were essentially the same in all treatments.7. Plasma pyruvate kinase (EC 2 . 7 . 1 .40) activity increased significantly in the trout deficient in both nutrients. This was thought to be due to leakage of the enzyme from the muscle and may be indicative of incipient (subclinical) muscle damage.The essentiality of dietary selenium for mammals and its close metabolic relation with vitamin E has been recognized since Schwarz & Folz (1957) first demonstrated that Se could replace vitamin E in the prevention of dietary liver necrosis. Results on this interrelation in fish are limited. Poston et al. (1976), using Atlantic salmon (Salmo salar) during the first six weeks after yolk sac absorption (mean weight 0.1 g), demonstrated that dietary supplements of both vitamin E and Se were necessary to reduce mortality significantly. In larger fish (0.9 g live weight) both vitamin E and Se were necessary to prevent muscular dystrophy. Hilton et al. (1980), using rainbow trout (Salmo gairdneri) of 1.28 g mean initial weight, could find no deficiency symptoms at dietary Se levels of 0.07 pg/g with 0.4 pg Se/l of rearing water and in the presence of a dietary vitamin E concentration of 0-4 IU/g. Both experiments were carried out at a water temperature of 14-15'.

Length-frequency data on squid (Loligo forbesi) collected during trawling surveys in Scottish waters from 1980 to 1994 were analysed to describe temporal and spatial patterns in abundance and to examine the prospects for using survey abundance to forecast fishery abundance. Loligo was patchily distributed in space and time. Distribution patterns in the North Sea in February appeared to be strongly related to bottom temperature (squid avoided waters <7 C) and, to a lesser extent, salinity (more squid in more saline water). For other areas and times, no temperature or salinity data were available, but there were trends for squid on the west coast to be more abundant in westerly areas and higher latitudes, and for squid at Rockall to be more abundant in shallow water. Inter-annual trends in abundance differed between the North Sea, west coast and Rockall, but average survey abundances for the North Sea and west coast tended to be positively correlated. For the North Sea and west coast, survey abundance was positively correlated with fishery abundance for the same month and area, and average abundance for the February North Sea survey was a reasonable predictor of commercial CPUE in the autumn of the same year (the peak of the fishery). Some of the observed trends were consistent with the existence of a stockrecruitment relationship but may indicate that abundance in a given calendar year is linked to climatic factors.

No abstract

1997. Distribution and seasonal prevalence of Hematodinium sp. infection of the Norway lobster (Nephrops norvegicus) around the west coast of Scotland. -ICES Journal of Marine Science, 55: 846-858.Around Scotland, coastal stocks of the commercially important Norway lobster (Nephrops norvegicus), particularly those within the Clyde Sea Area (CSA), have for some years been known to be infected by syndiniid dinoflagellate endoparasites of the genus Hematodinium. The prevalences of infected Norway lobsters in trawl samples from the CSA are reported for 1992-1995, together with similar data from a range of Scottish west coast sites in 1992, and from the Irish Sea in 1994 and 1995. In the CSA, infection prevalences declined after 1992 and were higher than those recorded in other sampled areas. Infection by Hematodinium was confined to the first half of the year, peaking in the spring and early summer, with medium-sized and female lobsters showng the highest prevalence. Comparison between CSA sites suggests that infection may be influenced by factors directly related to Nephrops age rather than size. In addition to the usual diel variability in catch, in spring male Nephrops showed diel variability in Hematodinium prevalence in trawl samples (being higher in the midnight samples). Females showed no diel variation in prevalence. Underwater television surveys of Nephrops burrow density and data on commercial landings indicate a decrease in Nephrops abundance in the last decade, which might in part reflect the higher levels of infection by Hematodinium during this time.1998 International Council for the Exploration of the Sea