Feeding Ecology of Humpback Whales in Continental Shelf Waters near Cordell Bank, California

Daytime feeding behavior of humpback whales (Megaptera novaeangliae) in Gulf of the Farallones, California, and adjacent waters was observed during autumn of 1988 to 1990. Bodega Canyon, Cordell Bank, and the Farallon Islands were the primary sites of feeding activity. Fecal samples of whales and zooplankton tows contained euphausiids exclusively, dominated by Thysanoessa spinifera (79%), with lesser amounts of Euphausia pacifica (14%), Nyctiphanes simplex (4%), and Nematoscelis difficilis (3%). In 1988 and 1990, whales also were infrequently observed feeding on small schooling fish, presumably Pacific herring (Clupea pallasii), northern anchovy (Engraulis mordax), and juvenile rockfish (Sebastes spp.). Feeding was the most common behavior observed (52%), and less frequently traveling (23%), milling (21 %), and resting (4%). Whales used different methods to consume euphausiid prey at the surface (0-10 m), in shallow water (11-60 m), and deep water (61-140 m). Humpback whales fed at the surface 56% of time in 1988 and 32% of time in 1990, using primarily lateral lunges to capture swarms of euphausiids. In 1989, no surface feeding was observed; however, deep, long-duration dives were followed by extended surface intervals with many respirations. These 1989 observations coincided with increased prey depth as indicated by depth sounder records of diving whales and prey scattering layers. In 1989, increased prey depth and associated feeding behaviors were strongly associated with unusually high surface temperatures, calm seas, and changes in water circulation. Environmental conditions in 1989 triggered the most intense and wide-spread occurrence of red tide in this region since 1980. Red tide samples collected throughout this period contained Alexandrium (=Gonyaulax) catenella and Noctiluca scintillans. Surface feeding was observed only in 1988 and 1990, when surface prey were available and red tides were very limited in extent, duration, and intensity. Annual variations in humpback whale feeding behavior were related to prey availability which is affected by corresponding environmental conditions. (PDF contains 94 pages)

Results of the first hydroacoustic survey of the Ugandan waters of Lake Victoria

A lakewide hydroacoustic research programme was designed in the Ugandan waters of Lake Victoria in order to ascertain the status of fish stocks. Data obtained from the hydroacoustic surveys were complemented with by catch data from multi mesh gillnets and frame trawls to validate acoustic estimates. Fish were distributed over the whole survey area, though the densities and species composition varied from place to place. Echo traces showed the fish formed schools during daytime and became more dispersed towards evening. Approximately equivalent indices of abundance were estimated for Rastrineobola argentea and Haplocromines. The distribution of the freshwater prawn, Caridina nilotica and the lakefly Chaoborus sp. was patchy. Dense swarms of Chaoborus larvae were observed to disperse from the lake bottom as the night approached thus assuring echo-traces formed by fish on the echogram and making their interpretation difficult. Caridina nilotica were observed to form dense echo-traces at the thermocline

A new synoptic survey of Northern Ireland lakes: sampling from the air

Northern Ireland has approximately 1670 lakes, which cover 4.4% of the land surface. However, most of the water area is accounted for by the large lakes such as Lough Neagh (385 km2) and Lower Lough Erne (109.5 km ). The majority of lakes are less than 100 hectares in area. They tend to be distributed towards the south and west of the Province, where extensive drumlin swarms are rich in small waterbodies. In 1988-1991, 610 of the 708 lakes between one and 100 hectares were sampled by the Northern Ireland Lake Survey. The objective was to assess their conservation status based on their aquatic macrophyte flora, but in addition to extensive plant surveys, the water of each lake was analysed for a range of chemical variables. This article reports on a full-scale survey carried out in early March 2002. The survey was taken with help of two helicopters. The authorise summarise the results of the chemical analysis of the survey.

Remote Camera and Trapping Survey of the Deep-water Shrimps Heterocarpus laevigatus and H. ensifer and the Geryonid Crab Chaceon granulatus in Palau

Time-lapse remote photo-sequences at 73-700 m depth off Palau, Western Caroline Islands, show that the caridean shrimp Heterocarpus laevigatus tends to be a solitary animal, occurring below ~350 m, that gradually accumulates around bait sites over a prolonged period. A smaller speies, H. ensifer, tends to move erratically in swarms, appearing in large numbers in the upper part of its range (<250 m) during the evening crepuscular period and disappearing at dawn. Trapping and photsequence data indicate the depth range of H. ensifer (during daylight) is ~250-550 M, while H. laevigatus ranges from 350 m to at least 800 m, along with the geryonid crab Chaceon granulatus. Combined trapping for Heterocarpus laevigatus and Chaceon granulatus, using a three-chamber box-trap and extended soak times (48-72 hr), may be an appropriate technique for small-scale deep-water fisheries along forereef slopes of Indo-Pacific archipelagoes.

Zooplankton standing stock and community structure along Karnataka Coast, west coast of India

Distribution of zooplankton along two transects at Karwar and Ratnagiri, west coast of India, was studied. The standing stock of zooplankton was relatively high in the neritic zone with the highest value [358 ml/100 m super(3)] in the area off Ratnagiri due to the aggregation of fish larvae and hydromedusae. Maximum zooplankton production in these areas was noticed with the low temperature and low dissolved oxygen during postmonsoon season. At Karwar the highest biomass [188 ml/100 m super(3)] was observed from the nearshore station due to swarms of the cladoceran Penilia avirostris and the pteropod Cresis acicula when the salinity was low. The fluctuations in numerical abundance and percentage composition of all the major planktonic groups are discussed. The fishery of these areas is compared with the zooplankton standing stock.

A record production from an integrated farming system utilising sewage enriched water

The results of experiments conducted on a pond dyke (655m²) in the Wastewater Aquaculture Division of the Central Institute of Freshwater Aquaculture, Rahara, during 1992-93 for maximising production through optimum utilisation of resources are communicated. Round the year intensive cultivation of okra (Abelmoschus esculentus), amaranth (Amaranthus gangeticus and A. viridus), water-bind weed (Ipomea aquatica), Indian spinach (Basella rubra), radish (Raphanus sativum), amaranth (Amaranthus viridis), cauliflower (Brassica oleracia var. votrytis), cabbage (Brassica oleracia var. capitota) and papaya (Carica papaya) was undertaken using the treated sewage water from fish ponds for irrigation. The pond dyke yielded 5,626.5 kg vegetable which worked out to 85.9 tons per ha per year. Multiple cropping with these vegetables excluding papaya on a 460 m² dyke recorded a production of 4,926.5 kg at the rate of 107.1t per ha/yr. An improved yearly net return of about 35% over investment could be achieved through the selection of highly productive and pest resistant vegetable crops of longer duration for integration into the system. Introduction of this type of integrated farming would enhance the overall productivity and returns from farming.