Ecological and economic consequences of hypoxia: Topic 2 Report for the Integrated Assessment on Hypoxia in the Gulf of Mexico

In this report we have attempted to evaluate the ecological and economic consequences of hypoxia in the northern Gulf of Mexico. Although our initial approach was to rely on published accounts, we quickly realized that the body of published literature deahng with hypoxia was limited, and we would have to conduct our own exploratory analysis of existing Gulf data, or rely on published accounts from other systems to infer possible or potential effects of hypoxia. For the economic analysis, we developed a conceptual model of how hypoxia-related impacts could affect fisheries. Our model included both supply and demand components. The supply model had two components: (1) a physical production function for fish or shrimp, and (2) the cost of fishing. If hypoxia causes the cost of a unit of fishing effort to change, then this will result in a shift in supply. The demand model considered how hypoxia might affect the quality of landed fish or shrimp. In particular, the market value per pound is lower for small shrimp than for large shrimp. Given the limitations of the ecological assessment, the shallow continental shelf area affected by hypoxia does show signs of hypoxia-related stress. While current ecological conditions are a response to a variety of stressors, the effects of hypoxia are most obvious in the benthos that experience mortality, elimination of larger long-lived species, and a shifting of productivity to nonhypoxic periods (energy pulsing). What is not known is whether hypoxia leads to higher productivity during productive periods, or simply to a reduction of productivity during oxygen-stressed periods. The economic assessment based on fisheries data, however, failed to detect effects attributable to hypoxia. Overall, fisheries landings statistics for at least the last few decades have been relatively constant. The failure to identify clear hypoxic effects in the fisheries statistics does not necessarily mean that they are absent. There are several possibilities: (1) hypoxic effects are small relative to the overall variability in the data sets evaluated; (2) the data and the power of the analyses are not adequate; and (3) currently there are no hypoxic effects on fisheries. Lack of identified hypoxic effects in available fisheries data does not imply that effects would not occur should conditions worsen. Experience with other hypoxic zones around the globe shows that both ecological and fisheries effects become progressively more severe as hypoxia increases. Several large systems around the globe have suffered serious ecological and economic consequences from seasonal summertime hypoxia; most notable are the Kattegat and Black Sea. The consequences range from localized loss of catch and recruitment failure to complete system-wide loss of fishery species. If experiences in other systems are applicable to the Gulf of Mexico, then in the face of worsening hypoxic conditions, at some point fisheries and other species will decline, perhaps precipitously.

Comparative fishing ability and economic efficiency of mechanised trawlers operating along the Kerala coast

This study was undertaken with a view to finding out the comparative fishing ability and economic performance of different fishing vessel sizes 9.15m (30'), 9.76m (32') and 10.97m (36') designed by the Central Institute of Fisheries Technology and operating along the Kerala coast. Data were collected from selected vessels of these sizes for four consecutive fishing seasons from 1964-65 to 1967-68. The catch/unit effort and total effort per year for the 10.97m (36') vessels were much better than those for the 9.76m (32') vessels. The yearly landings and the crew remuneration for the former were about twice those of the 9.76m (32') vessels. The economic efficiency of the 10.97m (36') vessels was also much better. The decline in landings per year in both size groups was more due to the reduction in the effort per year than the decline in catch/unit effort.

Mixed culture of fishes in seasonal ponds through fertilization and feeding

A study on mixed culture of mirror carp (Cyprinus carpio Lin.), tilapia (Oreochromis niloticus Lin.), silver carp (Hypophthalmicthys molitrix Val.) and Thai sharpunti (Puntius gonionotus Bleeker) in the ratio of 1:2:2:5 was conducted in 12 seasonal mini ponds (30 m² each) for 105 days. There were six treatments each with two replicates and each pond was stocked with a total of 100 fishes. Rice bran and mustard oil cake were used as supplemental feed either in combination or alone in presence or absence of fertilizer. Fertilizers were used in the form of organic, inorganic or both. The best growth performance of mirror carp, tilapia and Thai sharpunti was obtained in treatment III which received both fertilizer (organic+inorganic) and rice bran while the highest growth of silver carp was obtained in treatment VI receiving only inorganic fertilizer. However, the overall best production (2450 Kg/ha) and economic return for the culture period was obtained in treatment VI followed by treatment III. The results are discussed in the light of water quality parameters.

Social and economic implications of the fishery distribution patterns on Lake Victoria, Uganda

The fisheries of Lake Victoria have undergonea dramatic transformation during the last two decades. From being a locally based fishery with little intervention and capital investment from outside,the present fishery is dominated by national and international capital penetrating the industry. It is explosion in the growth of nile perch and the strong demand devloped for this fishin the global markets, which have transformed the fisheries of the Lake victoria. This report presents the results of a survey carried out between October 2001 and February 2002 about the fishery distribution patterns and their impacts on fisher communities of Lake Victoria. The fisheries distribution pattern of the lake is described as well as the flows and benefits from the fisheries resource and the resource constraints and sustainability options. A major part of the paper discusses some of the socio-economic impacts of the rapid changes that are responsible for the present fisheries. It particularly focuses on the effect of the Nile perch boom, its globalization and the development of the fish industry in Uganda, on food security and employment for the local population.

Effects of different types of feeds on growth and production of tiger shrimp, Penaeus monodon at Bagerhat region, Bangladesh

An experiment was carried out in farmers' gher (shrimp farm) at Bagerhat sadar upazilla, Bagerhat to ascertain the effects of three different types of feeds on the production and economics of brackishwater shrimp, Penaeus monodon for a period of 120 days. There were three treatments such as T1 (BFRI dough feed containing of 30% fish meal, 10% protein conc., 10% soya meal, 15% mustard oil cake, 18% rice bran, 5% maize, 10% wheat flour, 1% oyster shell powder and 1% vitamin premix), T2 (Commercial diet Saudi-Bangla grower) and T3 (Saudi-Bangla special feed). Each treatment had two replicates and the stocking of shrimp in each gher was 3 nos/m². Water quality parameters did not differ significantly among the treatments except water depth. Average production and net return of shrimp in different treatments varied from 404.0 to 509.0 kg/ha and Tk. 56,493.99-Tk. 84,209.60, respectively. T2 showed significantly (p<0.05) the highest production and economic return. The result of the study implied that T2 is more suitable and economically viable than that of other treatments for shrimp farming.