WETLAND ECOSYSTEMS

BAHAN KULIAHMANAJEMEN SUMBERDAYA PERIKANAN TAWARTAHUN AJARAN 2006-2007SEMESTER 6Oleh:SUTRISNO SUKIMINDepartemen Manajemen Sumberdaya PerairanFPIK-IPB2007

WETLAND ECOSYSTEMS Wetland is essential for the conservation of biodiversity, in terms of ecology, species and genetic diversity. The importance of wetlands is recognized, from an ecological point of view, wetlands are known to have high biodiversity Wetland play an important role in sediment, erosion and flood control; they Maintain water quality by reducing the impact of pollution, and maintain water supply and climatic stability through their role in global water and carbon cycles Wetlands support people by providing fisheries and agricultural and forest products

The Ramsar Convention defines wetlands as: “Areas of marshes, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six meters” In addition, the convention concludes that wetlands: “May incorporate riparian and coastal zones adjacent to wetlands, and island or bodies of marine water deeper than six meters at low tide lying within wetlands”

The Ramsar Classification System for Wetland Types: • Marine wetlands: • Shallow marine areas including shallow straits and lagoons • Tropical shallow waters such as coral reefs, seagrass beds and mangroves • The marine environment also includes a number of habitats in coastal zone such as mudflats, sandflats, beaches, and small offshore islands • Estuarine wetlands: • Wetland areas that located and influenced by estuaries • Wetland types such as mudflats and mangroves, delta • Lacustrine wetlands : • Inland inundated basins that have large water bodies: lakes, seasonal or irregular inundation, seasonal freshwater lakes including floodplain lakes

4. Palustrine wetlands: Palustrine often refers to swamp areas that are vegetated, either by emergent flora or forests Original palustrine wetlands may be peat, freshwater or mangrove swamps Peat swamps are characterized by peat soils, which vary in depth Peat soil may contain more than 65% organic matter Freshwater swamps are areas with less than 65% organic matter in their inundated soils • Riverine wetlands • Streams, rivers, waterfalls and associated wetlands are considered to be riverine wetlands • These types of wetlands also include inland deltas in large rivers and flooded river basins • Riverine wetlands often play an important role in hydrological systems and are commonly connected to other major wetland types.

Specific Criteria Wetland Ecosystems based on fish 1. It support a significant proportion of indigenous fish subspecies, species, or families, life history stages, species interaction and/or population that are representative of wetland benefits and/or values and thereby contributes to global biological diversity 2. It as an important source of food for fishes, spawning ground, nursery and/or migration path on which fish stocks, either within the wetland or elsewhere, depend: Mangrove areas at this site are likely tom have an important function as breeding and nursery ground for many marine animals, such as penaied shrimps, mullet, milkfish, sea perch, grouper, etc

Structure The description of the fishers’ interaction within the ecosystem requires identification of four main ecosystem compartments: (1) a biotic compartment, including target fish resources, associated and dependent species and the living habitat (seagrass, algal beds, corals); (2) an abiotic compartment, characterized by its topography, bottom types, water quality and local weather/climate; (3) a fishery compartment, in which harvesting and processing activities take place, with a strong technological character, and (4) an institutional compartment, comprising laws, regulations and organizations needed for fisheries governance. Humans are part of the biotic component of the ecosystem from which they draw resources, food, services and livelihood as well as part of the fishery component which they drive. These components interact and are affected by: (i) non-fishing activities; (ii) the global climate; (iii) other ecosystems, usually adjacent, with which they exchange matter and information; and (iv) the socio-economic environment as reflected in the market, relevant policies and societal values.

RIVER AND FLOODPLAIN ECOSYSTEMS According to Leopold et al. (1964) such a plain will typically include the following features: 1. River channel 2. Oxbow or oxbow lakes representing the cut-off portion of meander bends 3. Point bars, loci of deposition on the convex side of curves in the river channel 4. Meander scrolls, depressions and rises on the convex side of bends formed as the channel migrates laterally down-valley by the erosion of the concave bank 5. Slough, areas of dead water formed both in meander-scroll depressions and along the valley walls as flood flows more directly down-valley scouring adjacent to the valley walls

6. Natural levees, raised berms or crests above the floodplain surface adjacent to the channel, usually containing coarser materials deposited as flood flow over the top of the channel bank. These are most frequently found at the concave bank. Where most of the silt load in transit is fine grained, natural levees may be absent or nearly imperceptible 7. Backswamp deposits, overbank deposits or finer sediments deposited in slack water ponded between the natural levees and the wall of terrace riser

Riparian Vegetation Flood Forest Grass land Main river Flood lakes Flood plains High water level Low water level RIVER AND ITS FLOOD PLAINS OF INLAND OPEN WATERS OF INDONESIA

Natural Production of Systems The flood curve: In flood rivers the characteristics of the flood regime have been shown to control the fish community Examination of the biology of these community shows that, in general, the flood curve should have certain characteristics for the maintenance of good fish, production and species composition

The curve may be divided into 5 parts: (a). The rising limb: Once the flood has started to rise, increase in depth should be moderately steady as an intermittent rise with alternate spates and recissions is detrimental to the breeding of many species (b). The flood peak: While preservation of flooded conditions is advantageous for the growth of young fish (c). The period of falling water: This is especially critical (d). Low water: It is obvious advantage to the fish community to maintain the maximum amount of water in the system at low water, provided the floodplain itself is left dry

Production Studies of parameters of river fish populations show that patterns of mortality and growth within one year depend on the flood curve and do not follow the more normally used exponential models that are applied to the more stable lacustrine or marine fish populations

Figure: Within-year production curve obtained from “floodplain” models of growth and mortality. Normal production curve is shown for comparison.

A Conceptual Framework for Fish Community in Streams Low Habitat Heterogeneity: In areas with poorly developed pools, predominantly shallow depths, and low habitat volume, species richness, species density, and fish density are low because of the absence of deeper habitats needed The uniform shallow habitat results in a simple community As habitat heterogeneity, pool development, and habitat volume increase moderately, species richness, species density, and fish density increase because of the addition of older age groups

The unstable physical environment resulting from fluctuations in stream flow results considerable seasonal and annual variation in species richness, species density, fish density, and age structure Fluctuation in species composition may or may not occur, depending on the nature and timing of the physical disturbance, (2) the range of life-history within the community, and (3) whether the life-history patterns have stages or strategies to cope with the particular environmental disturbance

Fluctuation in species composition may or may not occur, depending on • the nature and timing of the physical disturbance, • (2) the range of life-history within the community, and • (3) whether the life-history patterns have stages or strategies to cope with the particular environmental disturbance Development of large, deep pools results in major changes in both community structure and the biological interactions hypothesized to be most critical in regulating community process. Species richness continues to increase with increasing habitat heterogeneity

Figure: Hypothetical of select fish community attributes along a gradient of increasing habitat heterogeneity and pool development in water stream.

FISH Fish Biology 1. Feeding Although a range adaptation for various feeding habits are present in fish species of floodplains. Some true specialists such as mud-eating or detrivore species do exist and often contribute a considerable part of biomass, but in other fishes specializations seem to be more directed at maintenance feeding during the severe periods of drawdown Most fish stop feeding almost completely during low water in tropical systems 2. Migration Migration is an essential part of the biology of the fish in flood-river systems and the phenomenon is so marks that many fisheries are based almost entirely on such movement Migration may be either longitudinal within the river channels or lateral from the river channel onto the floodplain

Type migration and movements: 1. Longitudinal migrations within main channel: these are usually upstream, but not always so 2. Lateral migration on to the floodplain 3. Local movements on the floodplain and distribution among flood-season habitats 4. Lateral migration from the floodplain towards the main channel 5. Longitudinal migration within the main channel: these are usually downstream but not always so 6. Local movements within the dry-season habitat: this may be the river, adjacent lake or in some cases the sea

Type of group freshwater fishes migration: 1. The “blackfish” species, whose migrations between dry-and-wet season habitats are restricted and which, at the most, undertake lateral migrations to the fringes of the main channel 2. Those species which undertake moderate movements within the river, but which spawn on the floodplain 3. The “whitefish” species which undertake an upstream migration during the dry season or early in the wet season, and some spawn upstream. Where upstream spawning occurs the adults usually return to the downstream floodplain habitats

3. Breeding The breeding of of river fishes is strongly influenced by flood regime Many species breed during the rising water, but this is by no means the only pattern Some species breed prior to the flood during low water, or at peak floods, but breeding during the period of falling water is comparatively rare Differences in breeding strategy are probably linked to the length of migrations to be undertaken as well as to the nature of river systems Breeding strategies other than migration to the headwaters are very diversified and are aimed at securing favourable conditions for the hatching, survival and growth of the larvae

Whitefish usually undertake long migrations toward the headwaters of the river and produced large numbers of eggs Blackfish are more likely to show elaborate reproductive behaviour including nest building, mouth breeding or internal fertilization coupled with parental care

Components of the fish fauna at flood rivers 1. Freshwater species The majority of fish inhabiting tropical rivers pass their lives in the freshwater parts of the system. In the estuarine zone of the coastal deltas the stenohaline species retreat before the saline water which penetrates upriver during periods of low flow. Certain species are more resistant to saline water and remain in the brackish water zone The larger species of fish in floodplain systems can be divided into two fairly distinct groups on the basis of their behaviour in response to the peculiar conditions of flood rivers

The first group of fishes ovoid severe conditions of floodplain by migration to the main river channel and frequently by more extensive movements in the river beyond the floodplain area • Members of this group are recognized as “Whitefish”: Cyprinidae • A few species are confined to the river channel at all times and never penetrate the plain • The second group of fish consists of species which have considerable resistance to deoxygenated conditions and which are termed “Blackfish”. • Their movement are therefore more limited than those of the whitefish. • They frequently remain in the standing waters of the floodplain during the dry period, and if they move to the river they remain within the vegetated fringes or in the pools of • the river bed as it dries Most siluroids belong to this category, together with ophiocephalids (channids), anabantids, osteoglossids, polypterids

2. Brackish-water species The estuarine zone of the coastal floodplain usually contains a complex of channels and lagoons where the salinity varies between freshwater and highly brackish, depending on the flood and tidal conditions The species living in these areas come from three sources; Freshwater stenohaline species, which enter the zone during the flood Marine stenohaline species, which penetrate inland during the dry season, and Complex of euryhaline species of freshwater or marine origin which inhabit the zone at all times of the year Euryhaline freshwater species: Cichlidae, Cyprinodontidae , siluroids. Euryhaline of marine species: Clupeidae, Atherinidae, Mugilidae, Lutjanidae, Sciaenidae, Ariidae, Pomadasyidae, Gerridae, Carangidae, Eleotridae, Gobiidae

3. Diadromous species Several species migrate between the river system and the sea, either for breeding or feeding Anadromous forms, where the breeding cycles is completed in freshwater, include several estuarine species of marine origin (example Eleotrids) Catadroumus species: Anguilla sp. Many normally marine species enter the lower reaches of rivers to feed during the dry season and return to the sea during the rains

Adaptation to extreme environmental conditions Many of the habitats within the floodplain ecosystem described above have extreme physical or chemical conditions which call for special adaptations on the part of the fish inhibiting them. Many of the adaptations are behavioural, involving migrations or local movements whereby the adverse conditions are avoided However, a certain section of the fish fauna has specific anatomical or physiological adaptations which permit the species concerned to survive low dissolved oxygen concentrations or even complete deoxygenation, high temperature and desiccation

Low dissolved oxygen concentration: Some species which inhabit the lentic waters of the floodplain are strangly sensitive to low oxygen levels There are two sources from which fish may obtain supplementary oxygen in poorly aerated waters: 1. the air above the water 2. the thin, but well oxygenated surface layer which is often only a few millimeters deep Many of the blackfish species inhabiting swamps have modifications which allow them to benefit from one or other of these sources by modifications for air breathing, whereas the rest used the surface layer as a source of oxygenated water

Respiratory modifications have been centred around three main anatomical systems: 1. the mouth and digestive tract, 2. the gills and branchial chamber 3. the lung or swim bladder The Anabantidae have labyrinth organs elaborated from the first gill arch. Modifications of the digestive tract for air breathing is made possible by the stopping of feeding during the dry season

WETLAND ECOSYSTEMS