Harmful and toxic algae

The chapter provides basic facts about harmful and toxic algae. It also discusses the conditions that stimulate their occurrence, different types of harmful and toxic algal blooms and their effects to fish and marine environment. The different strategies in coping with the problem of harmful and toxic algal blooms are also discussed

Harmful and toxic algae

The chapter provides basic facts about harmful and toxic algae. It also discusses the conditions that stimulate their occurrence, different types of harmful and toxic algal blooms and their effects to fish and marine environment. The different strategies in coping with the problem of harmful and toxic algal blooms are also discussed

Zooplankton distribution during winter using Two-Way Indicator Species Analysis (TWINSPAN) and Canonical Correspondence Analysis (CANOCO).

Spatial distribution and community structure of zooplankton species and its relationships with the environmental parameters (temperature, salinity, and turbidity and phytoplankton distribution) in some sandbanks of the Belgian coastal zone was carried out by the use of Two-Way Indicator Species Analysis (TWINSPAN) and Canonical Correspondence Analysis (CANOCO). There were 49 zooplankters identified all over the three sandbanks. Crustaceans was the most dominant sub-phyla represented mostly by copepods. Other members of plankton community were also present like cladocera, appendicularia, pteropoda and the larger omnivores and carnivores such as hyperiid, amphipod, chaetognath, ctenophore and fish larvae. TWINSPAN did not show a distinct division of the sandbank stations because of the presence of three dominant copepod species (Temora longicornis, Pseudocalanus elongatus and Centropages hamatus) in the three sandbanks. Canonical correspondence analysis (CANOCO) showed that species distribution of zooplankton was significantly affected by the environmental variables. This was due to lower salinity values observed around Buitenratel sandbank than Gootebank and Westhinder sandbanks. Two-Way Indicator Species Analysis analyzed spatial distribution and community structure of zooplankton species over the three sandbanks of the Belgian coastal zone based on species abundance. Canonical Correspondence Analysis (CANOCO) on the other hand, gave an idea on how far these subgroups were related to environmental variables

Economics of microalgae (Chaetoceros calcitrans) production using the multi-step method in the Philippines

The use of live microalgae for food during the early stages of the life cycle of shrimp larvae is considered essential. The microalga Chaetoceros calcitrans was mass produced at the Aquaculture Department of the Southeast Asian Fisheries Development Center (SEAFDEC/AQD) using the multistep method. The alga was grown in batches using successively larger containers. A cell density of 2.65 × 106 cells/ml was obtained from the final 4-day culture of C. calcitrans. Production cost using this method was P715.50/ton (US$ 1.00=25 Philippine pesos). The minimal costs involved in this method make it an affordable technique for the mass culture of microalgae

Economic analysis of bottom line and raft monoline culture of Kappaphycus alvarezii var. tambalang in Western Visayas, Philippines

A survey was conducted among 72 seaweed (Kappaphycus sp.) farmers in the Western Visayas region, Philippines, from March to July 1990 to assess their culture practices in terms of production and economic efficiency. Yields of 5.8 tons/ha per crop (dry weight) and 7.6 tons/ha per crop (dry weight) were obtained from bottom line and raft monoline methods, respectively. Investment requirement was P27361/ha for bottom line culture, and P56757/ha for raft monoline culture (P25=US$1). The bottom line method was more profitable with net farm income of P33286/ha per crop compared with P26365/ha per crop for the raft monoline method. The bottom line method of culturing seaweed is more cost-efficient compared with the raft monoline method. Production cost averaged P3.32/kg for the former method, and P5.55/kg for the latter method. Return on investment was also higher at 243% for the bottom line method and 93% for raft monoline

Winter distribution of phytoplankton and zooplankton around some sandbanks of the Belgian coastal zone

The distribution of phytoplankton and zooplankton around three sandbanks (Gootebank, Westhinder and Buitenratel sandbank) off the Belgian Coast was investigated in February 1994. The abundance of phytoplankton taxa was significantly different between the sandbanks. Community analysis using TWINSPAN resulted in a clear separation of clusters corresponding to the different sandbanks. The zooplankton community analysis, on the contrary, showed a rather indistinctive division of the sandbank stations. This was due to the omnipresence of three dominant copepod species (Temora longicornis, Pseudocalanus elongatus and Centropages hamatus). When these species were excluded from the analysis, a clearer distinction between the different sandbanks was found. The observed differences in phyto- and zooplankton species distribution could be explained by the position of the sandbanks. Westhinder is positioned further from the coast than Buitenratel, while Gootebank has an intermediate position. Buitenratel and Gootebank harbour typical coastal plankton communities, while the plankton community over Westhinder is clearly influenced by the Atlantic current penetrating the southern North Sea from the English channel. More phyto-benthic species were found at Buitenratel than at Gootebank, probably because of its limited depth. Thus, the Belgian coastal zone, which is considered as one box in most spatial descriptions of the North Sea plankton, in fact harbours heterogeneous plankton communities at the end of winter

Survival and settlement rates of Haliotis asinina larvae at different salinity levels

The study was conducted to determine the optimum salinity levels (24 ppt, 28 ppt, 32 ppt, 36 ppt and 40 ppt) for the survival and settlement rates of H. asinina in a complete randomized design with three replicates each. The experimental animals were reared in 15 glass aquaria for the first run and in plexiglass for the second run. Feeding of Navicula spp. was done once a day. Temperature and dissolved oxygen were monitored throughout the experiment. Data were analyzed using One-Way ANOVA to determine significant difference among treatments at 0.05 level of significance using Social Package for Social Science. Result of the first run showed that 32 ppt had the highest mean survival (1.50%) and mean settlement rate (1.84%). Similar result was also observed in 32 ppt with highest mean survival (9.72%) and mean settlement rate (16.42%). Significant difference existed among treatments during the second run of the experiment. Results showed that 28 ppt and 32 ppt were the optimum salinity levels for survival and settlement rate of H. asinina. Further study should be conducted to determine the tolerance and settlement rates of H. asinina larvae to lower salinities until it reaches juvenile stage with first respiratory pore appearing

Economic feasibility analysis of the monoculture of mudcrab (Scylla serrata) Forsskal

Mudcrabs, Scylla serrata Forsskal, were monocultured at different stocking densities: 5000, 10 000, 15 000 and 20 000/ha for 90 days. Highest mean weight, survival and relative growth increment (P>0.05) were obtained from a stocking density of 5000/ha. Best feed conversion ratio of 1.72 and corresponding gross production of 1019 kg/ha per crop were attained at the same stocking density. The economic indicators, i.e., return on investment and return on equity, were also highest at 5000/ha stocking density and the payback period was shortest. Partial budgeting showed that no incremental benefit accrued from stocking beyond 5000/ha. Sensitivity analysis showed that even if the value of mudcrab were to decrease by 28%, mudcrab monoculture would still be economically viable

Lipid nutrition studies on grouper (Epinephelus coioides) larvae

The main objectives of this project were to study the lipid chain transfer from the egg stage through hatching and the patterns of lipid conservation or loss during starvation and feeding of larvae in order to elucidate the lipid metabolism of grouper (Phase 1); to determine the fatty acid composition of highly unsaturated fatty acid (HUFA) boosters and enriched live food organisms to enable the possibility of choosing food organisms that provide various dietary levels and ratios of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (ARA, Phase 2); and to determine the effect of Brachionus and Artemia, containing different levels and ratios of DHA:EPA:ARA, on the growth and survival of grouper larvae (Phase 3). Total lipids (TL) of samples were extracted and separated into neutral (NL) and polar lipids (PL). The samples collected in Phase 1 were floating neurula eggs, newly hatched (NHL) and unfed 4-day larvae; larvae fed with live food organisms for 25 and 35 days or starved for 3 days; and wild-sourced larvae starved for a week. In Phase 2, the samples collected were phytoplanktons, Brachionus cultured in phytoplankton for 4 days, Diaphanosoma celebensis and Pseudodiaptomus annandalei. In phase 3, larvae were fed Brachionus until day 14 and at day 25 with Artemia. E. coioides eggs contained high DHA, EPA and ARA, demonstrating their importance in larval development. Larvae primarily spent NL as energy, whereas PL was generally conserved. Wild grouper larvae had higher levels of PL than NL, whereas hatchery-sourced eggs and larvae contained higher levels of NL than PL. Based on the lipid content of wild larvae, high phospholipid diets were essential for larvae survival and normal development. A variety of products were effective in enriching the HUFA content (particularly ratios of DHA, EPA and ARA) of live food organisms. HUFA-enriched live food organisms enhanced the growth, survival and pigmentation in grouper larvae

Amino and fatty acid profiles of wild-sourced grouper (Epinephelus coioides) broodstock and larvae

This study was undertaken to provide information on the levels of amino acids in the muscle, liver and gonad of wild-sourced broodstock and larvae, as well as in neurula eggs and day 35 larvae from a hatchery. The fatty acid composition of grouper broodstock tissues was also determined. Samples were analysed for crude protein, amino acids, total lipids and fatty acid contents. Muscle contained higher levels of crude protein and amino acids than the ovary and liver. At the early maturing stage, the grouper ovarian protein was 73.3% and lipid was 19.3%, indicating the high dietary requirements of these nutrients for ovarian development. The crude protein and amino acid contents in wild-sourced larvae were higher than that in eggs and larvae from the hatchery