The Population of the Non-indigenous Bivalve Arcuatula senhousia of the Varano Lagoon (Adriatic Sea,Italy)

A population of the invasive mussel Arcuatula senhousia(Benson in Cantor,1842)was monitored seasonally(May,July and October 2015)in the Varano lagoon,the largest brackish basin of Southern Italy,within the Gargano National Park,Central Adriatic Sea,in order to give information on the abundance,wet weight and frequency classes.The data were collected during a survey carried within the framework of the Regional Project FEP Apulia 2007/2013 “Identificazione di misure per una migliore gestione e conservazione della risorsa vongola nel lago di Varano(FG)”.Summer anoxia may have reduced the mussel population,resulting in less abundance,wet weight and average size in October than in July and May.In particular,about length data,two cohorts were observed in May and October 2015,while a modal distribution in July 2015.

Some aspects of the biology of the female blue crab Callinectes amnicola(De Rocheburne)from the Cross River estuary,Nigeria

Objective:To investigate some important aspects of the biology of Callinectes amnicola(C.amnicola)such as fecundity,carapace length-weight relationship,condition factor and carapace length frequency distribution from the Cross River estuary,Nigeria.Methods:A total of one hundred and twenty ovigerous females of C.amnicola,freshly caught with basket traps,lift net trap,and gill net were collected from the catches of the artisanal fisheries in the study area between June 2012 and May 2013.Fecundity,carapace length-weight relationship,condition factor and carapace length frequency distribution were determined and analyzed following standard methods.Results:Fecundity(F)ranged between 73090 eggs for crab of carapace length 8.1 cm and total weight 34 g and 809450 eggs for crab of carapace length 16.1 cm and total weight 395 g with a mean of 311808.93±17693.94 eggs.There was a positive significant relationship between fecundity and carapace length,total weight and condition factor as follows:F=6839.7CL^(1.4403)(r^(2)=0.2145,P<0.05),F=15302TW^(0.5798)(r^(2)=0.4079,P<0.05),F=147255K^(0.2788)(r=0.2717,r^(2)=0.0738,P<0.05).A significant linear relationship between carapace length and weight of C.amnicola is given by the equation:Log W=2.0447LogL–0.1389(r^(2)=0.3357,P<0.05).The crab exhibited a negative allometric growth pattern(b=2.0447).Condition factor ranged between 21.48 to 104.95 with a mean value of 47.21±2.17.The carapace length frequency distribution showed a unimodal class size distribution.Conclusions:Findings of this study is crucial in assessing the population dynamics and development of management strategies of the the Blue crab,C.amnicola from the estuary such as mesh size regulation,fishing season and fishing ground regulation in the Cross River estuary.Also,findings of this study will be useful in evaluation of the aquaculture potential of the Blue crab C.amnicola,which is a valuable shell fish for the inhabitants estuary.