A.A van Dam

The potential of fish production based on periphyton

Periphyton is composed of attached plant andanimal organisms embedded in amucopolysaccharide matrix. This reviewsummarizes research on periphyton-based fishproduction and on periphyton productivity andingestion by fish, and explores the potentialof developing periphyton-based aquaculture.Important systems with periphyton arebrush-parks in lagoon areas and freshwaterponds with maximum extrapolated fish productionof 8 t ha−1 y−1 and 7 t ha−1y−1, respectively. Experiments with avariety of substrates and fish species havebeen done, sometimes with supplemental feeding.In most experiments, fish production wasgreater with additional substrates compared tocontrols without substrates. Colonization ofsubstrates starts with the deposition oforganic substances and attraction of bacteria,followed by algae and invertebrates. Afterinitial colonization, biomass density increasesto a maximum when competition for light andnutrients prevents a further increase. Often,more than 50% of the periphyton ash-free drymatter is of non-algal origin. Highest biomass(dm) in natural systems ranges from 0 to 700g m−2 and in aquaculture experiments wasaround 100 g m−2. Highest productivity wasfound on bamboo in brush-parks (7.9 gC m−2 d−1) and on coral reefs (3 gC m−2 d−1). Inorganic and organicnutrients stimulate periphyton production.Grazing is the main factor determiningperiphyton density, while substrate type alsoaffects productivity and biomass. Better growthwas observed on natural (tree branches andbamboo) than on artifical materials (plasticand PVC). Many herbivorous and omnivorous fishcan utilize periphyton. Estimates of periphytoningestion by fish range from 0.24 to 112 mg dm(g fish)−1 d−1. Ingestion rates areinfluenced by temperature, fish size, fishspecies and the nutritional quality of theperiphyton. Periphyton composition is generallysimilar to that of natural feeds in fishponds,with a higher ash content due to the entrapmentof sand particles and formation of carbonates.Protein/Metabolizable Energy (P/ME) ratios ofperiphyton vary from 10 to 40 kJ g−1.Overall assimilation efficiency of fish growingon periphyton was 20–50%. The limited work onfeed conversion ratios resulted in valuesbetween 2 and 3. A simple simulation model ofperiphyton-based fish production estimates fishproduction at approximately 2.8 t ha−1y−1. Together with other food resources infishponds, total fish production with thecurrent technology level is estimated at about5 t ha−1 y−1. Because grazingpressure is determined by fish stocking rates,productivity of periphyton is currently themain factor limiting fish production. Weconclude that periphyton can increase theproductivity and efficiency of aquaculturesystems, but more research is needed foroptimization. Areas for attention include theimplementation and control of periphytonproduction (nutrient levels, substate types andconformations), the ratio of fish to periphytonbiomass, options for utilizing periphyton inintensive aquaculture systems and with marinefish, and possibilities for periphyton-basedshrimp culture.

A comparison of fertilization, feeding and three periphyton substrates for increasing fish production in freshwater pond aquaculture in Bangladesh

Abstract A polyculture trial was conducted in earthen ponds in Bangladesh to compare traditional aquaculture techniques (fertilization only or fertilization plus feeding) with a combination of the same techniques and periphyton substrates. Three substrates (bamboo, jutestick and bamboo side shoot) were tested. Rohu ( Labeo rohita ), catla ( Catla catla ) and kalbaush ( L. calbasu ) were stocked at a 60:40:15 stocking ratio and at a total stocking density of 11,500 per hectare in 15 earthen ponds with five treatments: standard fertilization as input (Control), control plus supplemental feeding with rice bran and oil cake (Feed), control plus bamboo substrate (Bamboo), control plus jutestick substrate (Jutestick) and control plus bamboo side shoot substrate (Kanchi). Water quality, plankton and periphyton were monitored throughout the experiment. Significantly higher ammonia concentrations were recorded in Control and Feed treatments. The chlorophyll a concentration of pond water was significantly higher in the Feed treatment than in the Jutestick treatment. Dry matter content and mean abundance of the periphyton communities were higher in the first and the last month of the experiment without significant difference among the three substrate types. Periphyton chlorophyll a concentrations per unit surface area did not vary significantly among different substrate types but increased throughout the experimental period and decreased with increasing water depth. Specific growth rates of rohu and catla were higher in Substrate and Feed treatments than in the Control treatment. Combined net yields of fish in Control, Feed, Bamboo, Jutestick and Kanchi treatments were 1226, 1960, 2098, 2048 and 2032 kg ha −1 135 day −1 , respectively. Production in substrate systems was significantly higher (ANOVA, P

The effect of periphyton and supplemental feeding on the production of the indigenous carps Tor Khudree and Labeo fimbriatus

Two experiments were conducted, one with the herbivorous mahseer Tor khudree and another with the fringe-lipped carp Labeo fimbriatus to study the effect of feeding and periphyton on their growth and production. Twelve tanks (25 m2) with mud bottoms and 0 (control), 98 (low density) or 196 (high density) bamboo poles tank−1 were used. Mahseer (initial wt. 3.5 g) and fringe-lipped carp (initial wt. 0.73 g) stocked at 25 fish tank−1 were reared for 90 and 60 days, respectively. Fish in half of the tanks received a pelleted feed (35% protein) at a ration of 5% body weight day−1. Water was monitored daily for dissolved oxygen, pH, temperature, and Secchi disc visibility, and weekly for ammonia, nitrate, phosphate, and alkalinity. Periphyton dry matter, ash, and chlorophyll content were quantified fortnightly. Periphyton biomass, measured as total pigment (chlorophyll-a+pheophytin), decreased with time in both experiments indicating effective grazing by the fish. In the control treatment (without supplemental feed and substrates), mahseer grew to a final weight of 30.8±0.9 g and fringe-lipped carp to 19.1±1.1 g (mean±S.D.). Supplemental feeding alone resulted in higher final mean weight of mahseer and fringe-lipped carp of 38.3±0.6 and 22.9±1.2 g, respectively. The provision of substrates resulted in final mean weights of mahseer of 36.0±5.7 and 36.1±1.3 while that of fringe-lipped carp were 22.8±1.2 and 22.5±1.9 (low and high density, respectively). Net production of mahseer with substrates was 41% and 51% higher, and that of fringe-lipped carp was 43% and 75% higher than in the control (low and high density, respectively). The combination of substrates and supplemental feed resulted in mean final weights of mahseer of 40.3±0.4 and 39.7±1.2, and of fringe-lipped carp of 23.6±1.4 and 25.5±0.1 (low and high substrate density, respectively). Production of mahseer with a combination of substrates and feeding was 71% and 54% higher, and of fringe-lipped carp, it was 85% and 87% higher than in the control (low and high density, respectively). It is concluded that the provision of substrates can reduce the need for artificial feed and can be an alternative to feeding in the culture of herbivorous fish.