Marine Wetlands Research Articles

FISH AND FISHERIES OF WETLANDS

SUMMARY The three major wetland types have characteristic fish communities. River-associated wetlands harbour a rich diversity of fishes which can either survive habitat desiccation during the dry-down, or migrate to and fro with the flood. Endorheic wetlands have a lower diversity of species which are typically ‘r’-selected relative to mainstream riverine or lacustrine forms. Marine wetlands have a variety of peripheral or marine forms, but are not discussed in this account. The dynamics of wetland fish communities are determined by periodically changing abiotic factors, especially water temperature and water level, and biotic factors, especially food availability. Water level fluctuations have several important functions and result in pulses of nutrient input and fish abundance. Wetland fish stocks can usually be sustained as long as the pristine flood regime is retained, but disruption of the flooding pattern interferes with fish breeding and nutrient flow. Fishing yields may be directly correlated with the flood history during the previous two years. Wetland fishes play an important role by converting the resource at the base of the food chain, i.e. living plants, detritus or epiphytes, into food for higher trophic levels. The need to identify and conserve key food supplies is emphasized. Wetland fisheries are relatively poorly developed in southern Africa with notable exceptions, e.g. Pongolo floodplain, Okavango swamp, Lake Liambezi, Elephant Marsh on the Shire River, but even in these systems the resource is probably underutilized. The need to consider the socio-economic implications of upgrading a subsistence fishery are emphasized, and further study on the effect of water level fluctuations on major trophic pathways and on multispecies fisheries is encouraged. Because of the urgent need to manage wetland fisheries, various short-cut methods to obtain first-order estimates of fish production, yields and growth rates should be used until more data are available. The need to manage a floodplain holistically for both the aquatic and terrestrial phases is stressed. In addition, inocula (re-colonizing life history stages) should be conserved to accelerate the recovery of endorheic wetland fish stocks after a drought. As wetlands are of fundamental importance to lake or river metabolism and provide vital breeding and feeding areas for fishes, they should be given the highest conservation priority. Cost-benefit analyses should therefore be performed before any large scale manipulations of wetlands are performed.

Marine parks and wetlands as natural reserves important for the ecological balance of the Mediterranean Sea

Abstract Degradation of the Mediterranean ecosystems has strongly increased over the last three decades and several characteristic floral and faunal elements are threatened by total destruction. The situation concerning existing and potential marine parks and wetland reserves was reviewed during the consultation meeting organized by UNEP in collaboration with IUCN, which took place in Tunis in January 1977. It appeared that only 20 smallsized marine parks and reserves exist at present. Not more than two wetland reserves have a satisfactory level of protection. Many species of animals and plants are doomed if urgent measures for the survival of their vital habitat are postponed any longer. In the present article a number of action points is indicated to cope with the immediate threats to a number of highly endangered or vulnerable species. Measures of a more general nature are recommended to achieve a firm basis for nature conservation in the Mediterranean area. The desirability for a masterplan for the entire Mediterranean basin, which could be developed by UNEP in collaboration with IUCN, is stressed. Such a plan should from the basis for further national and regional planning in all Mediterranean countries. A table is included to indicate the existing and potential sites of marine parks and wetland reserves in the Mediterranean countries.

Economic Values Attributable to Virginia's Coastal Wetlands as Inputs in Oyster Production

Coastal marine wetlands, in their natural state, are important biological and hydrological resources. Wetlands yield numerous valuable services such as provision of nursery and feeding habitat for fish and wildlife, and the assimilation of wastes. Wetlands, when filled or otherwise altered, also provide valuable sites for residences, marinas, or ports. Because well defined and vendable property rights are lacking for natural unaltered wetland services but are available for development services, the unregulated market will tend to reflect only the benefits of development. The result has been a rate of conversion of tidal wetlands that has been unsatisfactory to many individuals.