Recent trends in the climate of the tropical Pacific region

EXTRACT (SEE PDF FOR FULL ABSTRACT): Observations of climate variables in the tropical Pacific region are examined for the period 1970-1994. We look at a variety of climate variables, including upper ocean temperatures, surface wind stress, precipitation, and the Southern Oscillation Index (SOI) and find evidence for two distinct decadal-scale warmings in the tropical Pacific ocean-atmosphere climate system during this period.

Can lake sediments provide a record of tropical storms? The case of Laguna de Juanacatlan, Jalisco, Mexico [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Laguna de Juanacatlan is a small (15 hectare) lake in the State of Jalisco, Mexico. Its sediments are predominantly varved and thereby offer the potential of a high resolution paleoclimatic record.

Environmental inventory and the distribution of inorganic nutrients in a tropical estuary of the south-west coast of India

Dissolved nutrients (PO sub(4)-P, NO sub(3)-N, NO sub(2)-N and SiO sub(4)-Si) estimated in the surface and bottom waters of five selected stations of the Paravur Lake, Kerala, India, during February 1987 to January 1988 revealed distinct seasonal variations. Rainfall and land drainage play significant roles in the nutrient economy, particularly NO sub(3)-N and SiO sub(4)-Si, of this water body. Abnormally high values of PO sub(4)-P indicated extremely polluted condition at the wetting zone of the lake during the premonsoon season. SiO sub(4)-Si showed significant negative relationship with salinity.

Recent advances in tropical freshwater aquaculture

Several technological advances have been made in tropical freshwater aquaculture during the last three decades. Hatchery production of carp seed was achieved in India and China towards the late 1950's. Channel catfish farming in the U.S. has grown phenomenally. Development of the technology of high density culture using artificial aeration and nutritionally balanced diets has revolutionized freshwater aquaculture, particularly in Israel. Culture of fishes in cages, pens and running water have helped to achieve very high production levels. Considerable research work has been done on fish nutrition during recent years. Investigations on sex control reveal that it is possible to produce a single sex progeny which is more desirable for culture.

Limnological studies of a freshwater tropical impoundment : Powai Lake. 1: Morphometry and physical features

Powai Lake, an impoundment, came into existence in 1891 when the riverlet Dhanisar was dammed to conserve rainwater for drinking purpose. However, the water was found to be unpotable and the lake was leased out to the Angling Association, Bombay, exclusively for angling and sports. The lake is located about 27 km in the northeast of Bombay city at a height of 55m above MSL. It is rainfed with an average rainfall of 2,400 mm. The maximum waterspread area is 220 ha with a maximum capacity of 8.11 million m super(3) in the peak monsoon period when the water overflows the dam. There is no drawdown from the lake. Fluctuation in the water level is mainly due to evaporation and percolation. Transparency is low mainly due to suspended organic particles. There is hardly any difference in the water temperatures of surface and bottom, hence the annual heat budget is low at 2,818 cal m super(-2).

The freshwater zooplankton of Sri Lanka, with a discussion of tropical freshwater zooplankton composition

Based on the study of over 500 zooplankton samples collected in Sri Lanka during 1965-1974, the species composition from different habitats is analysed. The zooplankton assemblage is typically tropical with relatively few species of Cladocera and Copepoda. The Rotifera include a large number of species of the genus Brachionus. The limnetic zooplankton resembles the pond zooplankton closely in that all the eurytopic species found in the different types of habitats, including ponds; also occur in the limnetic zooplankton. The large Cladocera belonging to the genus Daphnia are very rare. In general, large zooplankters are absent. The size composition of the zooplankton has a smaller range than in temperate regions. This is due to the absence of large-sized zooplankton species. The reasons for the differences in species variety and size composition between zooplankton of temperate and tropical regions is perhaps due to a number of factors. These include the effects of high and uniform temperatures, food availability and predation by fish and invertebrates.

Distribution of mercury in a tropical estuary (India) situated near a chloro-alkali plant

The distribution of mercury in water, sediment and some biological samples of the Rushikulya estuary, east coast of India were assessed during Jan-Dec. 1989. Both the dissolved plus acid leachable mercury contents in water and the sediment mercury discerned conspicuous spatial and seasonal fluctuations. Adsorption on to the suspended particulates was found to be the most likely mechanism for removal of mercury from the water column. Exchange of mercury from sediments to water was observed at high salinities (20-30x10-3). The residual mercury contents in the biological samples revealed that bio-accumulation by bottom-dwelling organisms are higher than the pelagic components.

Freezing characteristics of tropical fishes 1. Indian oil sardine

The influence of different pre-freezing ice storage periods on the biochemical and organoleptic qualities of Indian oil sardines (Sardinella longiceps) in the individual quick frozen (IQF) and block frozen (BF) forms and frozen storage at temperatures of -12°C and -23°C was studied. The shelf-life of the sardines varied between 24 and 2 weeks for samples iced for 0 to 5 days prior to freezing. The deterioration in quality was accompanied by considerable increase in the peroxide value (PV) and free fatty acid (FFA) content and decrease in salt extractability of the proteins. These changes were more rapid at -12°C than at -23°C. BF sardines appeared to be better than IQF samples with respect to the biochemical changes although the differences in overall organoleptic quality were not significant.

Freezing characteristics of tropical fishes 2. Tilapia (Tilapia mosambica)

Tilapia from fresh water and brackish water-sources behaved differently during iced and frozen storage. The former showed an ice storage shelf life of about 13 days while the latter showed signs of spoilage beyond 10 days. In their respective freezing characteristics, the samples from the two sources exhibited far more significant variations. The fresh water type iced for 13 days preserved well for over 24 weeks when frozen and kept at a temperature of -18° C, while the brackish water variety held in ice for 10 days and subsequently frozen gave a shelf life of only 8 weeks under similar conditions.

Studies on smoke curing of tropical fishes

Fresh mackerel (Rastrelliger kanagurta), catfish (Tachisurus dussumeri) and sole (Cynoglossus dubis) were gutted, cleaned, washed, brined, and smoked. Though it contributes to the quality of the smoked products, salt does not appear to prevent bacterial growth or spoilage at low concentration. In heavily salted products, salt is found to have a definite preservative action. Smoking lasted roughly 5 hrs for mackerel and 4 hrs for sole. Increasing the smoking time gave the product an unpleasant taste. Fish were then sun-dried to 20% moisture. The fish had been prepared in three groups, (1) turmeric-treated, (2) propionate-treated and control. Turmeric treated samples had a very attractive appearance, especially sole. The course of spoilage, as measured by following changes in total volatile nitrogen content, is tabulated. All controls were spoiled within 3 months; the others remained in good condition for 6 months. Turmeric is considered to be an ideal preservative.

Freezing characteristics of tropical fishes III. Spotted seer (Scomberomorus guttatus)

Skin-on fillets of spotted seer were frozen individually with different pre-freezing ice storage periods, and stored at -23°C and -l0°C. The frozen storage shelf life was evaluated, with respect to holding time in ice prior to freezing, by examining the extent of oxidative rancidity, protein denaturation, organoleptic changes etc. Fillets with pre-freezing ice storage periods of 0, 3, 5 and 7 days had frozen storage shelf-life of 32, 24, 20 and 16 weeks respectively at -23°C. The fillets stored in ice for more than 7 days are unsuitable for further processing. Storage temperature greatly affected keeping quality of frozen fillets. Freshly frozen fillets stored at -10°C became unpalatable at 16-20 weeks as compared to 28-32 weeks for the fillets stored at -23°C.

Biology of fouling in Neendakara port, a tropical estuary in the south west coast of India

Species composition and some aspects of the biology of the fouling community in Neendakara port (southwest coast of India) has been examined for a period of one year. Fouling organisms were collected with a system of glass panels exposed for varying durations and during different months in the port. One species of sponge, nine species of coelenterates, thirteen species of polyzoans, four species of mud-tube dwelling polychaetes, four species of serpulids, one species each of mud-tube forming amphipod and tanaid, two species of oysters, six species of mussels and not less than eight species of tunicates were the macro fouler which settled over the panels. Monthly and seasonal settlement of the different species has been recorded. Fouling has been a continuous process occurring throughout the year in Neendakara port with slightly fluctuating biomass and considerably varying species composition. Alternate species dominance of marine and brackish water forms has been an important feature of fouling in the area. Number of species of the sedentary fouling animals represented on test panels has been high during the highly saline pre-monsoon period and low during the monsoon period.

The bacteriology of oil sardine (Sardinella longiceps) and mackerel (Rastrelliger kanagurta) caught from tropical waters off Cochin. 1 - Quantitative aspects

The total aerobic viable plate counts (TPCs) of skin, gills and intestine of newly caught oil sardine (Sardinella longiceps) and Indian mackerel ( Rastrelliger kanagurta) at four different temperatures, namely 36 ± 1°C, 28 ± 2°C (RT), 8 ± 1°C and 1 ±1°C, are reported. The total plate count at RT of the skin of oil sardine and Indian mackerel were in the range of l0 super(3) to 10 super(7) and 10 super(4) to 10 super(6) per cm², that of gills in the range of 10 super(5) to 10 super(9) and 10 super(4) to 10 super(8) per g and that intestine in the range of 10 super(5) to 10 sueper(9) and 10 super(5) to 10 super(8) per g respectively. The TPCs were markedly affected by the incubation temperature. Incubation at 28 ± 2°C gave the highest count; at 36 ± 1°C and 8 ± 1°C, the counts decreased by nearly 1-2 log cycles from that at RT. Incubation at 1 ± 1°C registered the lowest count. The peak values for bacterial counts of these fishes occurred at different periods of the year.

The bacteriology of oil sardine (Sardinella longiceps) and mackerel (Rastrelliger kanagurta) from tropical waters off Cochin. 2. Qualitative aspects

80% of the flora of skin, gills and intestines of oil sardine and mackerel at isolation temperature 28 ± 2°C consisted of Gram negative asporogenous rods or cocci, belonging to the genera Vibrio, Pseudomonas, Moraxella, Acinetobacter and Flavobacteria/Cytophaga. Nearly 10% of the flora was constituted by Gram positives, Micrococcus and Arthrobacter. Incubation temperature of 36 ± 1°C recovered more Vibrio spp. and Gram positives, while at lower temperatures of 8 ± 1°C and 1 ± 1°C, more Pseudomonas, Acinetobacter and Moraxella spp. were recovered. Significant changes with respect to season were observed in the relative distribution of different genera.