Pond Boss Forums MANAGING AN EXISTING POND Fertilization Phosphorus content of fish

The nitrogen and phosphorus content of two temperate fishes, Rutilus rutilus and Perca fluviatilis, and six tropical fishes, Oreochromis niloticus, Cichla monoculus, Serrassalmus rhombeus, Plagioscion squamosissimus, Prochilodus brevis and Hoplias malabaricus, were investigated to test the hypothesis that variation in body P content and N:P ratio is related to body size. Regressions of %P and N:P ratios against fish size (length and mass) confirmed the hypothesis for P. fluviatilis and P. squamosissimus, suggesting that body size is an important factor driving body P content and N:P ratios in some fishes. Moreover, significant increases in %N and N:P ratio with body size was found for H. malabaricus, a common piscivorous fish of the Neotropics. Interspecific variation in %P and N:P ranged two-fold and significant differences (P < 0·05) were found among the tested species. The mean ±s.d. elemental content across all fishes (n= 170) was 10·35 ± 1·29% for N and 3·05 ± 0·82% for P, while the N:P ratio was 8·00 ± 2·14. Data on fish body nutrient content and ratio will improve parameterization of bioenergetics and mass balance models and help clarify the role of fishes in nutrient cycles in both temperate and tropical freshwaters. Nitrogen and phosphorus content of some temperate and tropical freshwater fishes M. C. Dantas, J. L. Attayde, First published: 04 January 2007

The nitrogen and phosphorus level in fish tissues of Clarias gariepenus and Lates niloticus harvested from Zaria eutrophic waters were investigated for a year. Results showed high percentages of moisture and organic contents during the rainy season, while high percentages of dry matter and ash contents were observed during the dry season. The results also showed high mean percentages of water content in flesh (79.81±0.25%) at E2 with highest wet season range as (80.10 – 80.30%), dry matter content in heart (28.04±0.15%) at E2 with highest dry season range as (28.30 – 28.70%), organic content in kidney (94.80±0.12%) at E2 with highest wet season range as (94.80 – 95.50%) and ash content in gills (10.61±0.17%) at E1 with highest dry season range as (9.90 – 10.40%). There were no significant differences in the proximate composition between fish tissues and between species (P>0.05). The result also revealed high mean concentration of nitrogen (2.155±0.259%) and phosphorus (0.083±0.02%) all at E2 in Kidney. Nitrogen is significantly higher in the fish tissues (P<0.05) in all the sites. The results also showed that the levels of nitrogen and phosphorus in the tissues of the species harvested from eutrophic waters is above that of tissues from fresh water, but is within the recommended level for human consumption. From Chemsearch Journal 1(1): 19 - 23 Received: October, 2009 Accepted: May, 2010