A survey on some risk factors and evaluation of their impacts on streptococcosis incidence in rainbow trout farms in west of Mazandaran province

This study aimed to investigate the effects of 5- parameter dissolved oxygen, PH, nitrite, nitrate and temperature of the water on Streptococcosis incidence in two groups of fry and grower fish. Research was performed at west Mazandaran province -Tonkabon region in 12 rainbow trout selected farms. Research conducted in 3 farms with well source water, 8 farms with water source of the river of Dohezar and one farm with water source of the river of Azarood, during 12 consecutive months. From 1390.04.01 to 1391.04.01, once time each month, and in each time 10 fish randomly sampled, inlet water were sampled simultaneously Of 1350 sampled fish 607 fish with an average weight 22.04 gr, average length 12.59 cm were in fry category and 743 fish with an average weight 156.25 gr, average length 23.32 cm in were grower category. Streptococcosis observed only in grower category Of 72 fish with clinical signs of the disease, 14 numbers were positive Streptococcosis (19.44%) and 58 numbers were negative Streptococcosis (80.55%). Three fish from grower category has not any clinical signs of disease and seemed to be healthy but were positive Streptococcosis in examinations (0.22% of total fish sampled. Fish with clinical signs of the disease but negative Streptococcosis were of at least 55.1 gr and at most weight 417 gr respectively. The results showed that 47.07% cases of Streptococcosis happened at 15.6°C water temperature, 35.29% at 16.98°C and 17.64% cases happened at 18.04°C so that 100% of Streptococcosis cases was observed at the average temperature of 16.99°C. In addition, the survey results show that despite relatively high levels of nitrite in source water of farms from wells, nitrite does not effect on the disease incidence. It seems that an optimal level of dissolved oxygen in water is effective in reducing the effectiveness of nitrite in this disease. According to equation coefficients logit model is as follows: According to Logit model, it seems that for every degree change in temperature and pH of water, morbidity change will diminish 0.37 % and 1.74 % respectively. 80.56% of fish sampled that had the clinical symptoms, was ranging from an average weight of 5.1 gr (fry) and 417 gr (grower fish), that despite having clinical signs of the disease were negative Streptococcosis. Isolation of Staphylococcus bacteria as well as Gram-negative bacilli from fish with clinical symptoms similar to the symptoms of Streptococcosis, may indicate the involvement of other pathogens in fish clinical signs

Trout farms and other human activities effects on Cheshmehkileh river ecosystem in Tonekabon

Cheshmehkileh River and adjacent mountainous streams, play a strategic role as a historical axis for anthropogenic civilization, human welfare also habitat and migration pathway of commercial – biologic valuable fishes e.g. Caspian trout, Caspian kuttum, members of Cyprinidae family in south Caspian Sea drainage. Treats such as overfishing of Caspian trout and Red spotted trout stocks in mountainous headwaters, barriers construction and manipulations those are out of river carrying capacity developed by human activities, affected normal function of river as well. Sand mining big factories establishment next to the river, legal and illegal trade of river sediments, direct entry of Tonekabon landfill leakage into the river, development of Rainbow trout farms since 3 decades and huge effluents into the river containing dead fish and types of solids, escapement of cultured Rainbow trouts into the river, … are major minimum factors which needs basic information for integrating inclusively drainage management system. Cheshmehkileh River contains Headwaters of Dohezar (Daryasar & Nusha), Sehezar and Valamroud rivers during 13 monthly sampling phases between September 2009 and October 2010 based on macrozoobenthoses investigations by EPT, EPT/C EPA protocols, measurements of nominated physic-chemical and microbiologic parameters. Probability of Rainbow trouts escapement and invasion, existence, nutrition in Cheshmehkileh environment indeed investigated. Data analysis explained significant differences (P<0.05) between groups of measured parameters in different sampling stations. Dendogram of clustered analysis based on consolidation of major biologic/ physic-chemical and microbiologic parameters, separated stations No. 1, 3, 2, 4 in one group and remained classified in different groups. Station 8 and 9 similarly separated which expressed general similarities according to Sehezar river environment which were differs in comparison with other stations. Station 11 separated according to its natural quality of water and environment. Similarities between station 10 to Sehezar river stations 8 and 9 expressed general influence of Sehezar River more than Dohezar River in Cheshmehkileh condition especially in station No. 10. High scores of EPT and EPT/C indices in upstream stations 1, 3 and 8 also low score of indices in stations 7, 13 and 6 expressed levels of environment quality between these groups of stations. Maximum average biomass of macroinvertebrates belongs to Trichoptera order in Cheshmehkileh River. Significant decrease of biomass in stations 11, 12 and 13 in comparison with other stations stated environment degradation in mentioned stations relevant to excessive sand mining as well. Pollution resistant groups of invertebrates significantly increased in downstreams against upstream stations. Also disappearing of Plecoptera order in station No. 7, 9, 10 and 13 stated low quality of environment in comparison with upstream stations. Confirmation of effects quality and quantity for point and non-point sources of imported pollutants require specific management considerations in order to present exploitations, pollutants control and emergencies for river monitoring in forthcoming years