One thousand eight hundred specimens of Tilapia zillii (Gervias) from Tiga Lake, Kano, Northern Nigeria were examined using hand lens and microscope between July, 2007 and June 2008 for parasites , 782 (53.4%) of these were infected. Parasites recovered were, Clinostomum spp. 74(4.1%) Procamellanus spp. 111 (6.1%), and Protozoa Cyst 198 (11.0%). Adult fishes were more infected than the juvenile, females were significantly more infected (P <0.05). Infection increases with length and body weight. Physio-chemical parameter of the lake was good and infection rate was high wet season and low in dry season. The presence of these parasites might elicit some pathological effects on the fish by retarding their growth, causing tissue description and even death.

The aim of this work is to investigate piscine parasites of gills and intestinal tract of Clarias gariepinus. Six hundred and forty five (645) specimens of specie were examined fortnightly for a period of one year from November, 2006 to October, 2007. One hundred and fourteen (114) and one hundred and ninety nine (199) were infested fish samples from gills and gastrointestinal tract respectively. Parasites recovered during the survey include two species from gills identified as Ergasilus sarsi ((24.60%) a crustacean (copepod), and one protozoan (myxosporean) named Henneguya sp (11.82%). However, parasites recovered from the GIT composed of four different specie of Cestodes (35.53%) comprising of Anomataenia sp, Bothriocephalus aegypticus, polyonchobothrium polypetri and polychobothrium sp, two species from nematodes (28.13%), with Procaamallinus laevionchus and unidentified specie. All these parasites were located in the intestinal lumen of the specie with the exception of Anomataenia and Procaamallinus species dominating the stomach region only. Females samples had higher incidence rate 235 (75.5%) than males 78 (24.9%), there was no significant difference (P>0.05) in infestation rate. Incidence of infestation among the three sized classes showed adults were mostly infested (69.03%) followed by sub adults (26.82%) with juveniles (4.2%) being the least parasitized. There was significant difference in incidence rate (P<0.05) among the three classes. Analysis of results indicated size influenced the degree of infestation rates in adults' size. And the sex of host did not influence the incidence of the parasites.

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Research was carried out to explore the fish species diversity and study some aspects of the Biology of fish of Daberam reservoir, Katsina state, for a period of three month from March to May 2009. 66 Samples of fish were collected from commercial fishermen and experimental fishing gears, preserved in formalin and taken to laboratory for identification. Seven genera comprising eleven species were identified. The regression coefficient (b) were 3.07, 2.91 and 3.21 for the three most commercially importance species in the reservoir i.e. Oreochromis niloticus, Tilapia zilli and Clarias gariepinus respectively, the results indicated Positive allometric growth for O. niloticus and C. gariepinus and negative allometric growth for T. zilli. The mean condition factor (k) was 1.140, with values of 1.027, 1.660, and 0.732 for O. niloticus, T. zilli and C. gariepinus respectively. This result indicates that the fish are not leaving well compared to other freshwater fishes.