scholarly journals Fluxes of Physicochemical Parameters in The Cross River Estuary, Nigeria

2021 ◽  
Vol 4 (3) ◽  
Keyword(s):  
Surface Water ◽  
Temporal Variation ◽  
Physicochemical Parameters ◽  
Field Data ◽  
River Estuary ◽  
Surface Water Temperature ◽  
Cross River ◽  
Standard Methods ◽  
The Cross ◽  
Cross River Estuary

Study on the fluxes of physicochemical parameters and nutrients in the Cross River estuary ecosystem was under taken between June, 2016 and April, 2017. Field data were collected bimonthly at five stations and analysed both insitu and in the laboratory using standard methods. The monthly mean surface water temperature ranged from 26.68±0.74 OC in June 2016 to 33.6±7.84 OC in October 2016, salinity ranged from 0.10±0.12 ‰ in October 2016 to 10.20±2.80 ‰ in March 2017, and DO from 2.740±0.563 mg/l in June 2016 to a maximum of 5.340±2.152 mg/l in January 2017. Values obtained for PO4 , SO4 , NO3 , DO, and BOD in this study were below the permissible limits [1]. There was significant (p < 0.05) temporal variation in all the parameters studied (PO4 , NO3 , SO4 , DO, BOD5 , salinity, temperature and transparency). There was no significant (p > 0.05) spatial variation in PO4 , NO3 , SO4 , temperature and transparency. Parameters studied showed both positive and negative correlations. The implications of these findings are discussed.

Studies on fecundity and spawning of blue crab (Callinectes Amnicola) in Cross River Estuary

2021 ◽  
Vol 36 (1) ◽  
pp. 75-82
Author(s):  
J. Otoyo ◽  
S.M. Ameh ◽  
O.K. Achema
Keyword(s):  
Blue Crab ◽  
Egg Size ◽  
Gonadosomatic Index ◽  
Carapace Width ◽  
River Estuary ◽  
Hepatosomatic Index ◽  
Cross River ◽  
The Cross ◽  
Cross River Estuary ◽  
Egg Diameter

Studies on identification of species, fecundity and development stages of blue crab, (Callinectes amnicola) were investigated at the Cross River Estuary between the months of December, 2018 and May, 2019. The parameters used for the study were gonadosomatic and hepatosomatic indices, egg diameter and counts. All measurements followed standard procedures. Gonadosomatic index was at its peak in December (88.9) and April (83.3). This coincided with the peak in egg size suggesting that spawning occurred twice within the period.The low values of hepatosomatic index around December (1.20) and April (0.45) added to confirm the spawning in these months. The species spawns at a mean egg size of 17.55mm. The dimension of crabs examined were in the following range: carapace length 40.0 to 70.0mm, carapace width, 5.0 to 60mm and body weight 40.0 to 140.0g. The relationship between fecundity and weight of crab was  significant (r = 0.295: p<0.05), indicating positive correlation. Absolute fecundity of the species ranged between 1,375 and 225,132 eggs. The smallest crab with egg had a carapace width of 39.5mm and weight of 46.9g. Spawning at this size seems to be a strategy adopted by the species to cope with exploitation pressure. The result of this study revealed that C. amnicola had a high reproductive potentials. Hence, adequate regulation is required to enhance sustainability of the species in the Cross River Estuary.

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