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Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Griffith School of Environment, Science, Environment, Engineering and Technology, This thesis provides significant insight into the effect of seasonal patterns of flooding on estuarine function in the wet-dry tropics by exploring the impact of seasonal freshwater flow on benthic biota in the wet-dry tropical Norman River estuary of northern Australia. This thesis also describes the construction of a model designed to predict the potential impact of freshwater flow regulation on key estuarine biota. Flow regimes in the wet-dry tropics are characterised by seasonal patterns of summer wet season floods and low or no freshwater flow for the rest of the year. Few studies exist on wet-dry tropical estuaries, and none have sampled the estuary before, during and after wet season floods of different magnitude. Research within this thesis has increased the understanding of estuarine function in the wet-dry tropics, and the short and long term impacts of the magnitude of wet season flooding on benthic biota (meiofauna and microphytobenthos) was identified. These findings were combined with information on commercially important banana prawns (Penaeus merguiensis) in the Norman River estuary to construct a Bayesian Network (BN) model. The model explored the drivers of change in the Norman River estuary under currently natural patterns of flow, and the likely impact of future water resource development on banana prawns and their key food source, meiofauna and MPB (microphytobenthos).

This thesis provides significant insight into the effect of seasonal patterns of flooding on estuarine function in the wet-dry tropics by exploring the impact of seasonal freshwater flow on benthic biota in the wet-dry tropical Norman River estuary of northern Australia. This thesis also describes the construction of a model designed to predict the potential impact of freshwater flow regulation on key estuarine biota. Flow regimes in the wet-dry tropics are characterised by seasonal patterns of summer wet season floods and low or no freshwater flow for the rest of the year. Few studies exist on wet-dry tropical estuaries, and none have sampled the estuary before, during and after wet season floods of different magnitude. Research within this thesis has increased the understanding of estuarine function in the wet-dry tropics, and the short and long term impacts of the magnitude of wet season flooding on benthic biota (meiofauna and microphytobenthos) was identified. These findings were combined with information on commercially important banana prawns (Penaeus merguiensis) in the Norman River estuary to construct a Bayesian Network (BN) model. The model explored the drivers of change in the Norman River estuary under currently natural patterns of flow, and the likely impact of future water resource development on banana prawns and their key food source, meiofauna and MPB (microphytobenthos)., Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Griffith School of Environment, Science, Environment, Engineering and Technology, Full Text

The nursery function of mangroves as shelter has been postulated to explain the positive correlation between shrimp catches and mangrove area. This study was undertaken to document shelter use and other activities in mangrove‐associated penaeids and to determine diel and size differences relating to these activities. Juvenile Metapenaeus ensis, Penaeus latisulcatus and P. merguiensis collected from mangrove areas in Guimaras, central Philippines and stocked individually in glass tanks (= replicates) provided with artificial shelters and sand substrate were observed every hour for 25 h. Size classes tested were very small (1–5.9 mm carapace length); small (6–10.9mm CL); medium (11–15.9mm CL); large (16–20.9mm CL); and very large (21–25.9 mm CL). Due to limited juvenile supply, only 3 sizes were tested for each species: P. merguiensis (very small to medium), M. ensis (small to large) and P. latisulcatus (medium to very large) with 5 replicate animals (one per tank) per size. Juvenile M. ensis and P. latisulcatus showed a strong diel periodicity of daytime burial and nocturnal activity. In contrast, P. merguiensis showed active swimming and feeding throughout the day and night. Very small to small P. merguiensis were observed on the shelters, but burying was exhibited only by a few medium‐sized juveniles. This shelter use is consistent with observations of small P. merguiensis entering the mangrove forest (where roots, twigs, etc. contribute to structural complexity) on the flood tide and concentrating in the shallow, turbid waters of adjoining creeks during ebb tide and slack water.

A study on the biogenic amines in the haemolymph of penaeid prawn, Penaeus merguiensis, at different stages of ovarian growth was conducted. The gonadosomatic index (GSI) was used to show the stages of the ovarian growth. The qualitative and quantitative determination of the biogenic amines were accomplished by using the high performance liquid chromatography with electrochemical detection (HPLC-ECD) method, which provides a high sensitivity and selectivity in determining the biogenic amines. The biogenic amines can be detected at the picogram levels using this method.

The manual provides information on the diseases that affect the 3 major species of shrimps cultured in the Philippines: Penaeus monodon, P. merguiensis and P. indicus. It includes the common name of the disease, causative agent, species affected, stages affected, gross signs, effects on the host and methods of prevention and treatment. This revised edition includes newly discovered diseases. It is hoped that the manual will be of considerable help to shrimp farmers in identifying the disease and lead to prevention or early disease diagnosis and control.

A study on the biogenic amines in the haemolymph of penaeid prawn, Penaeus merguiensis, at different stages of ovarian growth was conducted. The gonadosomatic index (GSI) was used to show the stages of the ovarian growth. The qualitative and quantitative determination of the biogenic amines were accomplished by using the high performance liquid chromatography with electrochemical detection (HPLC-ECD) method, which provides a high sensitivity and selectivity in determining the biogenic amines. The biogenic amines can be detected at the picogram levels using this method.

For sustainable management of mangrove ecosystems, there is a pressing need to increase our knowledge of fish and invertebrates associated with this system. This study sampled microhabitats (89–258 m2) inside the mangrove forest at Pagbilao, the Philippines, on two consecutive spring tides using stake nets. Distribution patterns of shrimps and fish were compared among four microhabitats that differed in dominant mangrove species (Avicennia marina, A. officinalis or Rhizophora apiculata), structural complexity of the root system, and proximity to open water habitat. A 5 to 6-year-old replanted Rhizophora microhabitat was also sampled to study faunal recolonization following replantation. The mean (±SE) density of the shrimp community was 1·5±0·2 shrimps m−2, dominated by Palaemonidae, followed by Acetes sp., Penaeus merguiensis and Metapenaeus ensis . The highest shrimp density was observed in the replanted Rhizophora habitat, which also had the highest structural complexity. The mean (±SE) density and biomass of the fish community was 5·1±2·0 fish m−2and 10·4±3·3 g m−2, respectively, dominated by Ambassis kopsi, A. urotaenia and Atherinomorus balabacensis. The fish community preferred the pneumatophore (Avicennia) microhabitats to the prop root (Rhizophora) habitats. Highest fish abundance and biomass were observed in the most inland habitat, which also lacked larger (total length >100 mm) carnivorous fish. The results demonstrate the extensive use of intertidal mangrove forests by vagile fauna, as well as the successful recolonization by shrimps and fish of replanted Rhizophora habitat. The role of mangroves as predation refuges, based on the distribution pattern of shrimps and fish, is discussed. Sampling strategies in mangrove intertidal habitat are also outlined.

A total of 4845 penaeids belonging to nine species—Metapenaeus anchistus, M. ensis, M. moyebi, M. philippinensis, Penaeus merguiensis, P. monodon, P. semisulcatus, P. latisulcatus and Metapenaeopsis palmensis—were collected by pocket seine monthly over 13 months from mangrove and non-mangrove sites in Guimaras, Philippines. The restricted distribution of the three dominant species—M. ensisandP. merguiensisto the brackish water riverine mangrove, andM. anchistusto the high-salinity island mangrove and tidal flat—is probably related to different salinity and substrate preferences. Abundance and size composition of the major species suggest a strong nursery role for the riverine mangrove (high juvenile densities, relatively small sizes year-round), limited nursery use of the island mangrove (fewer shrimps, larger size ranges, presence of maturing females) and a non-nursery use (e.g. foraging) in the tidal flat. Penaeid recruitment to the river had two peaks in November and May when the average salinity was ∼20 (Practical Salinity Scale) and water temperatures were high (30–31 °C). The spatio-temporal pattern of penaeid species in Guimaras shows partitioning across habitats and seasonal recruitment influenced by physical and biological factors.

The manual, an updated version of the 1984 SEAFDEC/AQD manual, presents the underlying principles and step-by-step instructions of prawn larval and post-larval rearing. The techniques described are not only applicable to Penaeus monodon, but may also be modified and applied to other penaeid and metapenaeid species. The following aspects are covered: Site selection; Life cycle; Hatchery design and planning; Hatchery operations; Diseases; and Economics.

The manual, an updated version of the 1984 SEAFDEC/AQD manual, presents the underlying principles and step-by-step instructions of prawn larval and post-larval rearing. The techniques described are not only applicable to Penaeus monodon, but may also be modified and applied to other penaeid and metapenaeid species. The following aspects are covered: Site selection; Life cycle; Hatchery design and planning; Hatchery operations; Diseases; and Economics.

The report describes the activities of the Center during the year 1989 regarding the various research studies conducted, and the training, extension, and information services provided.

The manual provides information on the diseases that affect the 3 major species of shrimps culture in the Philippines: Penaeus monodon, P. merguiensis and P. indicus. It includes the common name of the disease, causative agent, species affected, stages affected, gross signs, effects on the host and methods of prevention and treatment.

A microsporidian parasite found to invade the ovaries of the white prawn, Penaeus merguiensis de Man, 1888, causes the whitening of the mature female gonads. Ultrastructure examination of the white ovaries reveal the presence of spores and other developmental stages of the parasite. The earliest stage observed is the schizont which contains a few cisternae of endoplasmic reticulum, many ribosomes and a thin plasma membrane. The next stage is the sporont characterized by a pansporoblast membrane, an increase in the amount of endoplasmic reticulum, appearance of more vesicles and of polar filament precursors. Diplokaryotic schizonts and sporonts are also found. Division of the sporonts gives rise to uninucleate sporoblasts. At this stage, the spore organelles start to form and the cell acquires a degree of plarity. The polar filament and the polar sao appear and the sporont membrane complex develops into a sporoblast wall. The sporoblast is transformed into a spore with a polar cap, posterior vacuole, polaroplast, and two laters of spore wall, the exospore and the endospore. The polar filament is a tubular structure consisting of seven coils which after the second coil taper abruptly distally. All these stages of development of the parasite are observed in the infected ovaries within which its life cycle is completed. A probable mode of transmission and life cycle of the parasite is presented.

Electron microscopy of the ovary of the white prawn, Penaeus merguiensis De Man reveals the presence of the different stages in the life cycle of a species of microsporidia. This is the first such report of microsporidian infection of prawns, locally or abroad. Heavy infection causes the whitening of the entire ovary and the inability of spawners to spawn, a condition which unless controlled is a serious threat to prawn culture. Studies are being undertaken with the end in-view of controlling and/or preventing the infection.

The manual provides information on the culture of shrimps and prawns. Considerations regarding farm sites, pond specifications, pond ecosystems and differences between prawn and milkfish culture are examined. Seed supply, farm management practices and economic aspects are detailed.