DYNAMICS AND EXPLOITATION OF FISH RESOURCES NEAR THE MOUTH OF THE MARKHAM RIVER, PAPUA NEW GUINEA (SUBSISTENCE FISHERY, MARINE ECOLOGY, COMMUNITIES)

A nocturnal demersal nekton assemblage was sampled fortnightly for two years at five sites in the Labu estuary using a 3m beam trawl with a 3.2cm stretched mesh net. Forty species were caught, totaling 31,458 individuals with the five most abundant species comprising over 95% of the catch. Using multiple regression techniques with Fourier transformations, the mean number of species, the mean abundance, and mean weight, were found to conform to a regular annual cycle with maxima in April and May. Seven of the eleven most abundant species demonstrated regular annual cycle of abundance. Diurnal catches were much smaller than nocturnal catches with the greatest catches occurring from 1700 to 2200hr. There was no lunar variation of abundances and biomass between catches, more species were caught during full moon periods. Salinity and temperature values in the estuary exhibited an annual cycle with maxima occurring in February/March. Several species were significantly correlated with physical data. Several species exhibited a greater variation in abundance and mass between years than within years, supporting the hypothesis that in the tropics, between year variation in coastal marine biotic communities is greater than within year variation.;The Labu fishery used a variety of equipment that were generally not species or size selective in several locations to fish a diverse tropical fish assemblage. This is probably an important factor in maintaining a high catch per effort. This balanced approach to exploitation serves as equilibrium between subsistence fishermen and their resource. Catches during the "drought" year of 1982 were less than 1981. The dredging associated with the Lae port expansion is likely to have an obvious deleterious effect on resource populations at the most popular and productive fishing site, the mouth of the Markham River, at least during construction. The use of an offshore site for spoil disposal would result in less socio-ecological disruption.;The subsistence fishing activities of the Labu Butu village south of the Markham River, Morobe Province were documented by interviewing 12,399 fishermen for 2 years, representing over 82,000hr of fishing. The annual catch was estimated at 15-34 tonnes prawns, 41-75 tonnes finfish and 10-15 tonnes larval fish. The larval fish fishery had the highest catch rate at 5kg/hr/person versus 0.7kg/hr for finfish.