No abstract

The annual mean trophic level (TrL) of marine fish landings along the Indian coast consisting of 53 exploited species/groups was estimated for the period 1950-2002. The landings as well as TrL increased along the northwest (NW) and southwest (SW) coasts. However, increase in the landings was associated with decrease in mean TrL along the east coast, particularly along the southeast (SE) coast at the rate of 0.04 per decade. The increasing trend of the FIB index ceased in the last 5-10 years along three coasts. A backward-bending signature in the landings versus TrL plot for the SE coast in the last 6 years indicates fisheries-induced changes in the ecosystem owing to low productivity of the coastal waters and high density of fishing craft. The landings of most of the large predators increased along the Indian coast, but higher removals appear to have helped proliferation of their prey, the mid-level carnivores. Fishing the food web has been influenced by environmental fluctuations, advanced fishing technologies, and market-driven, deliberate fishing on low-trophic level (TL) invertebrates such as the penaeid prawns.

a b s t r a c tThe response of the Arabian Sea to global warming is the disruption in the natural decadal cycle in the sea surface temperature (SST) after 1995, followed by a secular warming. The Arabian Sea is experiencing a regional climate-shift after 1995, which is accompanied by a five fold increase in the occurrence of ''most intense cyclones". Signatures of this climate-shift are also perceptible over the adjacent landmass of India as: (1) progressively warmer winters, and (2) decreased decadal monsoon rainfall. The warmer winters are associated with a 16-fold decrease in the decadal wheat production after 1995, while the decreased decadal rainfall was accompanied by a decline of vegetation cover and increased occurrence of heat spells. We propose that in addition to the oceanic thermal inertia, the upwelling-driven cooling provided a mechanism that offset the CO 2 -driven SST increase in the Arabian Sea until 1995.

No abstract

Reared in (tubular) aquaria containing different depths of water, OphiocephaJus striatus (0.7 g, 4.5 cm body length), an obligatory air·brea thing tropical fi sh, swam long or shon distances to enable themselves to exchange atmospheric air. In eaeh tested depth (2.5,5.0, 15.5, 31.0 and 40.0 em) series, one group was starved. while the other was fed ad libitum twice a day on fish muscle. In the shallowest water (2 .5 em depth), the feeding group surfaced 1,294 times, travelling 64.7 m at an energy cost of 20A mg dry fish substance / g live fish / day, against those exposed to the deepest water (40 em depth), which expended 35.8 mg/ g/ day, swimming I ,503A m on 1,879 visits to the surface. The starving group surfaced only 482 times, travelling 24.1 m at an expense of 5.8 mg / g/ day in the shallowest water, while those at 40 cm depth surfaced 504 times, swimming 403.2 m at an energy cost of 7A mg/ g/ day. Owing to the sustained swimming activity and the consequent fatigue , the test individuals belonging to both groups in all the tested series 'hang' to the surface for a definite interval, repaying the O 2 debt. Observations were also made to assess the duratio n of'hanging' to precisely estimate the distance travelled. Irrespective of cha nges in depths ofwatcr, the duration of'hanging' [0 su rface was on1y 3.0 hr/ day forthe fcedinggroups, wttile it was as much as 15.5 hr/ day for the starving groups. The maximum sustained metabolic level of O.striatus reared in 40 em depth was equivalent to 1.23 ml 0 2/ g/ hr, which is about 2 times higher than the value reponed fo r the active metabolism of swimming Oncorhynchus nerka at 15°C in Brett's (1964) respiromete r. O.striatus reared in 2.5 em depth fed 32.0 mg and converted 6.7 mg dry food / g live fish / day. while those exposed to the deepest water fed 49.1 mg, but converted only 5.5 mg! g/ day. Culturing obligatory air·breathing fishes in shallow waters will be advantageous.