Studies of physical, chemical, and biological oceanography in the vicinity of the Revilla Gigedo Islands during the “Island Current Survey” of 1957

ENGLISH: The tendency of the tunas, especially the yellowfin (Neothunnus macropterus) to be more abundant in the near vicinity of islands and seamounts, or "banks", than in the surrounding oceanic areas, is well known to commercial fishermen. This has been confirmed by statistical analysis of fishing vessel logbook records, which demonstrates that the catch-per-day's-fishing is, indeed, higher in the near vicinity of these features. It is hypothesized that islands and seamounts cause changes in the physical circulation or the biochemical cycle resulting in greater supplies of food for tunas in their immediate environs. In order to examine this hypothesis, and in order to study possible mechanisms involved, the "Island Current Survey" was undertaken from 8 May to 12 June, 1957, under the joint auspices of the Inter-American Tropical Tuna Commission and the Scripps Institution of Oceanography. Surveys of varying nature and extent were made from M/V Spencer F. Baird near Alijos Rocks, Clarion Island, Shimada Bank and Socorro Island (Figure 1). These studies sought to provide knowledge of the action of islands and seamounts in arresting, stalling or deflecting the mean current past them, in establishing convergence and divergence in the surface flow, in producing vertical motion (mixing and upwelling), and in influencing the primary production and the standing crops of phytoplankton and zooplankton. Each survey is discussed below in detail. Observations made at a front on 10 June will be discussed in another paper. SPANISH: Los pescadores que realizan la pesca comercial conocen muy bien la tendencia de los atunes, en particular del atún aleta amarilla (Neothunnus macropterus), de presentarse en mayor abundancia en las cercanías inmediatas a las islas y cimas submarinas, o "bancos", que en las áreas oceánicas circundantes. Este hecho ha sido confirmado par el análisis estadístico de los registros de los cuadernos de bitácora de las embarcaciones pesqueras, demostrándose que la captura par dias de pesca es, en efecto, más abundante en la inmediata proximidad de tales formaciones. Hipotéticamente se admite que las islas y las cimas submarinas provocan cambios en la circulación física o en el ciclo bioquímico, lo cual se pone de manifiesto a través de un mejor abastecimiento de alimento para los atunes en sus cercanías inmediatas. Con la finalidad de verificar esta hipótesis y de estudiar los mecanismos que ella involucra, se realizó la “Island Current Survey” del 8 de mayo al 12 de junio de 1957, bajo los auspicios de la Comisión Interamericana del Atún Tropical y de la Institución Scripps de Oceanografia. Con el barco Spencer F. Baird se hicieron observaciones de distintas clases y alcances cerca de las Rocas Alijos, la Isla Clarion, el Banco Shimada y la Isla Socorro (Figura 1). Estos estudios tuvieron por objeto adquirir conocimientos sobre la acción que ejercen las islas y cimas submarinas sobre la corriente promedio, ya sea deteniéndola, reduciendo su velocidad o desviando su curso, así como estableciendo convergencia o divergencia en su flujo de superficie, o provocando un movimiento vertical (mezcla y afloramiento) e influyendo en la producción primaria y en las existencias de fitoplancton y zooplancton. Cada operación será tratada a continuación por separado. Las observaciones hechas el dia 10 de junio sobre un frente serán objeto de otra publicación.

Preliminary studies on blanching of prawn

The paper represents results on the studies undertaken to find out the causes of irregular drained weight conditions in commercial canned prawn samples. The tendency of cooked prawn to attain the equilibrium moisture content (72-74% in M. affinis and M. dobsoni) when in contact with brine has been found to be mainly responsible for the loss and gaine in drained weight. Underblanching results in loss of moistures from the meat during processing. It has been found that under standard blanching conditions, which is independent of initial moisture content, salt concentration of the blanch liquor and the temperature of sterilisation, the fluctuation in the drained weight could be avoided.

Acute toxicity of copper, zinc and mercury on intertidal gastropods of Mumbai coast

The acute toxicity test conducted by static bioassay techniques have revealed that among selected heavy metals, copper is more toxic than zinc and mercury to Planaxis sulcatus and Trochus radiatus. The natural availability of heavy metals in the surrounding environment of these organisms is found to be deciding factor for their toxicity. Natural habitat of the animal also contributes to the sensitivity of a particular animal to the heavy metals tested. In addition the tendency of the animal to overcome the adverse conditions in their surrounding also plays a significant role in toxicity of pollutants.

Size related feeding patterns and electivity indices of silver barb (Barbodes gonionotus Bleeker) from a pond, Bangladesh

The feeding patterns with respect to quality and quantity of food of silver barb, Barbodes gonionotus varied with their size and development. The results indicated that the fish in the size group I (7-25 mm TL) were fairly omnivore with particular liking for rotifera, green and blue-green algae while the size group II (25.1-44 mm TL) and III (44.1-55 mm TL) were omnivore with higher tendency of feeding on debris, aquatic plants, green algae, blue-green algae and rotifera. However, the fish of the size group IV (55.1-80 mm TL) were found to be herbivore with feeding preference for aquatic plants, green and blue-green algae. In all the size groups, debris was the most dominant food item. Feeding preference of the fish showed clear ontogenetic shift. The electivity indices revealed that the fish were selective feeder.

Netzmaterial und Selektivität in der Ostseedorschfischerei

Since some time fishing gear scientists express their concern over an observed tendency of the commercial fishery to proceed from codend netting yarns of 3 to 4 mm to higher values or to switch to the use of double instead of single yarn. A recent large EU-financed project collected statistical evidence on the detrimental effect of such behaviour on the selectivity of the codends. In this context data on cod are very scarce. German-Polish experiments in the Baltic from 1999 to 2001 aimed at filling this gap. The investigations prove a clear evidence of a negativ ecorrelation between netting yarn diameter and selectivity factor and/or L50. In addition they demonstrate a clear negative effect on selectivity when switching from single to double yarn The effects are of an order of magnitude that counteracting effects as catch size are masked and support the decision of the IBSFC to define maximum yarn diameters both for single and double yarn netting. A measuring instrument for the enforcement of these new regulations was introduced right in time.

Relationship between El Nino and summer monsoon rainfall over Pakistan

The present paper deals with the influence of El Nino event on the summer monsoon rainfall over Pakistan. The correlation between monthly rainfall of summer monsoon season and bi-Monthly Multivariate ENSO Index (MEI) has been calculated to see the influence of El Nino on the summer monsoon rainfall. MEI is bimonthly ENSO Index pertaining to the period from first week of previous month to first week of the month under consideration. While study the correlation's with the ENSO events out side the Pacific Ocean MEI is more appropriate than other indices like Southern Oscillation Index (SOI) as MEI integrates complete information on ENSO viz. six oceanic and meteorological variables over the tropical Pacific. The results of the study show that there is a tendency of reduction in summer monsoon rainfall over Pakistan during El Nino years. The deficiency in % rainfall is statistically significant up to 90% level during July and September months. It is interesting to note that Pakistan receives more than normal rainfall during summer monsoon season in the immediate following year after the El Nino event. The correlation analysis is also performed on the summer monsoon months for individual provinces of Pakistan. All provinces receive deficient rainfall during monsoon months. The deficiency in rainfall over Punjab during all monsoon months is significant, whereas the deficiency in rainfall is significant during July and August over NWFP and Sindh respectively. No significant impact of El Nino on the summer monsoon rainfall over Baluchistan is observed.