The effect of a marine seismic exploration on fish populations in British Columbia coastal waters

The effect of a marine seismic exploration on fish populations in British Columbia coastal waters

Oceanographic Abstracts 131 50cm in the first half year, differ from one another from area to area. Thus, the length at which they become a major gr...

112KB Sizes 0 Downloads 17 Views

Oceanographic Abstracts


50cm in the first half year, differ from one another from area to area. Thus, the length at which they become a major group is 42 to 45 cm but it has no area characteristics. This discrepancy reflects the environmental diversity but, on the other hand, the similarity in length at the time of recruitment may be due to environmental unformity. The skipjack groups near Japan are presumably produced in an area where there is a tendency for environmental fluctuations and they migrate to the neighboring seas of Japan on reaching 42-45 cm in body length. This is also revealed by the fact that the recent increase in abundance has occurred concurrently in each area. In the Hawaii area, there are four age groups whose abundance is progressively greater in the following order, 3, 5, 4 and 2 year olds. They belong to a spawning group. Hence, the Hawaii area may be a marginal spawning area. The skipjack in the Eastern Pacific are mostly composed of the 2 and 3-year olds and there is little spawning there. There is a high correlation between the fluctuations in the abundance of skipjack in these two areas. According to Schaefer the skipjack in the Hawaii area is closely connected with that in the Eastem Pacific. Thus the skipjack in both areas belong to one common population having common elements and are the 2-3 year olds. When the fluctuation in abundance in the Northeastern Area is compared with those in the two areas mentioned above the directions of variation fairly coincide with each other. From longline data, there is a continuous distributional zone between Hawaii and Japan. In conclusion, the skipjack in the Northeastern area are closely interrelated with those in the Hawaii and Eastern Pacific areas, and therefore, a transpacific population with a common element, the 2 year olds, is believed to exist. The major spawning of the skipjack in the Pacific occurs in a relatively restricted area at the Equator west of 140°W. The effective spawning season is in mid-summer (of tbe Northern Hemisphere) and comparatively short. The larvae produced there are brought up in the environmental conditions with a common tendency of fluctuation, Thus, as they grow, the skipjack are recruited to the marginal areas and conversely come back to the central spawning area as they become older. KEARNS ROGER K. and FORBES C. BOYD, 1965. The effect of a marine seismic exploration on fish populations in British Columbia coastal waters. Can. Fish Cult. No. 34: 3-26. The Shell Oil Company of Canada conducted a marine seismic survey off the west coast of British Columbia during the summer months of 1963. Because of the potential damage t o local fish populations through exposure to high velocity explosives, the Department of Fisheries of Canada conducted a program of supervision and control on the Company's field operations. The Company agreed that the on-site departmental biologist would have full authority to suspend or terminate any shooting procedures judged to be detrimental to fish populations. Observations throughout the survey revealed that 419 (4"3 ~ ) of a total of 9,638 shot points exhibited a total surface mortality of 59,277+ fish. Herring and rockfish represented 72.2 and 23"8 % of the total kill respectively with the remaining four percent consisting of 189+ adult salmon, 467+ juvenile salmon and 1,732+ miscellaneous fishes. Large charges (50-300 lbs) of nitrone S.M., typic al of refraction shooting, killed more fish more frequently than light charges (5-25 lbs) typical o f reflection shooting. A n increase in detonation depth increased the area of potential fish kill. I n shallow water (less than 34 fms) the horizontal lethal range of a seismic explosion is greater than in deep water (greater than 34 fms). Surface observations of fish mortality were not a reliable measure of charge lethality since they do not account for subsurface mortality. Under existing operational conditions only the vertical scanner on the fish detection unit was found useful in detecting the presence of fishes. In view of the area covered and number of shot points subjected to high velocity explosives, the resulting fish mortality was considered relatively light. KINZER JOHANNES, 1965. Untersuchungen fiber das Makroplankton bei Ischia und Capri und im Golf yon Neapel im Mai 1962. IL Verbreitung der Siphonophora. PubbL Staz. Zool., Napoli, 34: 247-255. In the waters off Ischia and Capri and in the Gulf of Naples a total of 39 hauls with various types of plankton nets yielded 14 species of siphonophores. For the area of investigation, the species Rosacea plicata QuoY and G~aMARD, Lensia fowleri BIGELOW and L. multicristata MOSER were observed for the first time. The horizontal and vertical distribution of the species described are discussed. KtTAIC,ORODSKV S. A. and B. N. FILYUSHrdN, 1965. Theories of turbulent mixing in the upper layer of the ocean in application to the analysis of oceanographic and meteorological observational data. (In Russian; English abstract). Okeanolog. lssled., Rez. Issled. po programme Mezhd. Geofiz. Goda, Mezhd. Komitet, Prezidiume Akad. Nauk, SSSR, No. 13: 17-23. By means of the similarity theory for processes of vertical turbulent mixing an attempt was made to determine relationships between characteristics of a vertical temperature profile and parameters of dynamic and thermal regime in the upper layer. Two different concepts in determining the universal theoretical relationships arising from such interaction were discussed. The conclusions of these theories were checked using data of standard observations made at the Canadian " P a p a " station. KOMABAVASm M. and T. GOrqDA, 1964. Concentrations of chloride and deuterium in rainwater as a function of raindrop diameter and their relationship to rainfall intensity. J. meteorol. Soc., Japan, (2), Vol. 42 (6): 354-361. Rainwater was collected according to drop sizes by using a raindrop spectrograph. The chemical composition was measured and compared with the intensity of rainfall in each range of drop size.