โ Scribed by L. R. Haury
No coin nor oath required. For personal study only.
This study compares the small-scale (IOO's to 1000's of meters) horizontal spatial distribution of zooplankton from stations in the California Current (29~ 118~ and in the North Pacific Central Gyre (31~ 155Ow). Patterns were inferred from the spacing of vertical tows and the variability in abundance of 15 taxonomic categories caught in these tows. In the California Current, 4 tows were taken at random positions within 2000 m of a drogue or fixed geographic position and 4 replicate tows were taken at the drogue or the fixed point. Four series of these 8 tows were taken around noon and midnight during two days. At the Central Gyre station, two similar series (one day and one night) were taken while following a drogue~ Estimates of the scale of structure based on comparisons of replicate and random tow variability suggest that aggregated patterns in the Central Gyre are larger than a few hundred meters, while the California Current structures may be less than 100 m in size. Day-night changes in patch size were not apparent in either area. Evidence for multispecies patches was found only for the Central Gyre station. Replicate samples in both areas gave more consistent measures of community structure (relative proportions of species) than the random tows. Similarity of community structure decreased with increasing distance between tows being compared. The decrease was much greater for the California Current station, a further indication of smaller patch size in this area. Diurnal changes in community structure occurred in both areas.
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Analysis of video recordings of swimming in abyssal grenadiers __Coryphaenoides__ spp. revealed site differences in tailโbeat frequencies. At the highly oligotrophic deep central North Pacific (CNP; 5800โm depth) station fishes had significantly lower tailโbeat frequencies (0ยท73โยฑโ0ยท02โHz, meanโยฑโs.