tailieunhanh - Effects of temperature, wind and spawning stock biomass on recruitment of Arcto-Norwegian cod

This study examined the clinical findings of visual display terminal (VDT) users who presented with monocular symptoms. The sample consisted of 35 people performing sustained work at VDTs. Each subject un- derwent an evaluation that included: visual acuities, determination of refractive status, ocular motor testing, the stability of fixa- tion, degree of suppressions of simulta- neous binocular perception, and ocular health status. These findings were com- pared to a control group of 100 subjects who did not habitually use a VDT. Signifi- cant signs of unstable fixation/suppression were found with symptomatic subjects, as compared to the controls. We also found initial visual acuity differences between the two eyes of the VDT user group, but no sig- nificant refractive. | FISHERIES OCEANOGRAPHY Fish. Oceanogr. 4 4 278-292 1995 Effects of temperature wind and spawning stock biomass on recruitment of Arcto-Norwegian cod GEIR OTTERSEN AND SVEIN SUNDRY Institute of Marine Research . Box 1870 hlordnes 5024 Bergen Norway ABSTRACT Sea temperature has earlier been shown to have a large influence on rhe recruitment of Arcto-Norwegian cod Gadus morhua. We here hypothesize that this linkage is partly due to the direct effect of temperature on larval and juvenile growth. Secondly temperature acts as a proxy for both biotic and abiotic factors influencing recruitment. Indices of abundance of early juvenile cod 2-3 months old 0-group cod 4-5 months old and 3-year-old cod are analysed in more detail against the environmental temperature wind stress components wind-induced turbulent energy and the spawning stock biomass. To deal with autocorrelation non-stationar-ity and non-normality which complicate a statistical time series analysis randomization and Box-Jenkins methods are applied. In addition to the important effect of high sea temperature during the early life stage in forming strong year classes the results show that the spawning stock biomass is nearly as important. Also alongshore southerly wind stress anomalies during the period of pelagic drift from April through summer and offshore wind stress anomalies during egg and early larval stages in April act favourably on recruitment. The beneficial effect of southerly wind anomalies could be linked partly to high temperature but the flux of zooplankton-rich water from the Norwegian Sea into the feeding areas of the Barents Sea may also be increased. The favourable influence of offshore winds in April is less predominant and causal links are also less clear possible explanations for this might be increased offshore spreading of eggs and early larvae resulting in reduced risk of predation and increased compensation inflow of intermediate Norwegian Sea water which in this restricted period of

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