Fish Production Data Research Articles

Fish production in freshwaters: Are rivers more productive than lakes?

Community fish production data were summarized from the literature to test the hypothesis that production is higher in rivers than in lakes. Average community production at 55 river sites was three times greater (273 kg∙ha−1∙year−1) than at 22 lakes (82 kg∙ha−1∙year−1). Higher production (P) in rivers resulted from much higher densities of fish (14 times) and greater biomass (B) (about 2 times). Average fish weight and P/B ratios were inversely correlated. Average fish weight was 7 times less, and P/B ratios were 1.5 times higher (after correction for fish size), in rivers than in lakes. Thus, rivers not only had higher average biomasses of fish but also the turnover rate of the biomass was greater. Fish production was positively correlated with phosphorus in both lakes and rivers. Information on community fish production supported the hypothesis that the productivity of river habitat is, on average, higher than the productivity of lake habitat. The productive capacity of freshwater habitats can be predicted using a multiple regression model developed by Boudreau and Dickie (Can. J. Fish. Aquat. Sci. 46: 614. 1989), where fish production is calculated from average fish biomass and body mass.

Influence of site and season on water quality and tilapia production in Panama and Honduras

Data from 2 years of standardized experimental protocols in Panama and Honduras were analyzed to ascertain the influence of site and season on production of Oreochromis niloticus in earthen ponds. In Experiment 1, ponds were fertilized every 2 weeks with trip le superphosphate at 4 kg P 2O 2/ha, and were monitored to establish baseline of edaphic, climatic and fish production data. In Experiment 2, ponds were fertilized weekly with chicken litter at 125, 250, 500, or 1000 kg total solids/ha. Both experiments were repeated during wet and dry seasons at each site. Honduras ponds were more alkaline and higher in phosphorus than Panama ponds that were excavated in acidic soils. However, Honduras ponds were turbid with clay. The net result of acidic, nutrient-poor soils in Panama and clay turbidity in Honduras was low biological productivity at both sites for inorganically fertilized ponds. Primary productivity and net daily fish yield significantly increased with increasing chicken litter application ( P < 0.05). Primary productivity, chlorophyll a, and net daily fish yield were similar at both sites in ponds fertilized weekly with chicken sitter at 125–500 kg/ha; however, at the highest fertilization rate, primary productivity, chlorophyll a, and net daily fish yield were 57, 29, and 37% greater in Panama than in Honduras. Higher fish yield was significantly correlated with higher chlorophyll a and primary productivity. Lower primary production and net daily fish yield in Honduras were attributed to light limitation by clay turbidity.

Aquashade(R) Treatment of Channel Catfish Ponds

Three channel catfish (Ictalurus punctatus) ponds were treated with 4 mg/liter of the dye, Aquashade(R), and three ponds served as controls. The dye imparted a blue color to waters, but it did not appreciably affect Secchi disk visibilities. Decline in Aquashade(R) concentrations with time resulted primarily from seepage—concentrations decreased by about 0.75 mg/liter each month from April to August. Chlorophyll a concentrations and coverage of pond bottoms with underwater weeds did not differ significantly between dye-treated and control ponds. Average dissolved-oxygen concentrations were higher at dusk in control ponds than in treated ponds, but concentrations of dissolved oxygen at dawn did not differ between treated and untreated ponds. A fish kill, unrelated to the treatment, resulted in loss of fish-production data from one of the treated ponds. Net fish production averaged 3,010 kg/hectare in the three control ponds and 3,641 kg/hectare for two of the dye-treated ponds. Because no improvement in water quality resulted from treatment, the greater fish production in the treated ponds likely was related to random variation rather than to the application of Aquashade(R).