The Role of Turbulence in Broadcast Spawning and Larval
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Mapping and Distribution of Sabella Spallanzanii in Port Phillip Bay Final
Mapping and distribution of Sabellaspallanzanii in Port Phillip Bay Final Report to Fisheries Research and Development Corporation (FRDC Project 94/164) G..D. Parry, M.M. Lockett, D.P. Crookes, N. Coleman and M.A. Sinclair May 1996 Mapping and distribution of Sabellaspallanzanii in Port Phillip Bay Final Report to Fisheries Research and Development Corporation (FRDC Project 94/164) G.D. Parry1, M. Lockett1, D. P. Crookes1, N. Coleman1 and M. Sinclair2 May 1996 1Victorian Fisheries Research Institute Departmentof Conservation and Natural Resources PO Box 114, Queenscliff,Victoria 3225 2Departmentof Ecology and Evolutionary Biology Monash University Clayton Victoria 3068 Contents Page Technical and non-technical summary 2 Introduction 3 Background 3 Need 4 Objectives 4 Methods 5 Results 5 Benefits 5 Intellectual Property 6 Further Development 6 Staff 6 Final cost 7 Distribution 7 Acknow ledgments 8 References 8 Technical and Non-technical Summary • The sabellid polychaete Sabella spallanzanii, a native to the Mediterranean, established in Port Phillip Bay in the late 1980s. Initially it was found only in Corio Bay, but during the past fiveyears it has spread so that it now occurs throughout the western half of Port Phillip Bay. • Densities of Sabella in many parts of the bay remain low but densities are usually higher (up to 13/m2 ) in deeper water and they extend into shallower depths in calmer regions. • Sabella larvae probably require a 'hard' surface (shell fragment, rock, seaweed, mollusc or sea squirt) for initial attachment, but subsequently they may use their own tube as an anchor in soft sediment . • Changes to fish communities following the establishment of Sabella were analysed using multidimensional scaling and BACI (Before, After, Control, Impact) design analyses of variance. -
Population Dynamics of the Freshwater Clam Galatea Paradoxa from the Volta River, Ghana
Knowledge and Management of Aquatic Ecosystems (2012) 405, 09 http://www.kmae-journal.org c ONEMA, 2012 DOI: 10.1051/kmae/2012017 Population dynamics of the freshwater clam Galatea paradoxa from the Volta River, Ghana D. Adjei-Boateng(1),,J.G.Wilson(2) Received February 6, 2012 Revised April 25, 2012 Accepted May 7, 2012 ABSTRACT Key-words: Population parameters such as asymptotic (L∞), growth coefficient (K), recruitment, mortality rates (Z, F and M), exploitation level (E) and recruitment pattern mortality, of the freshwater clam Galatea paradoxa were estimated using length- growth frequency data from the Volta River estuary, Ghana. The L∞ for G. para- parameters, doxa at the Volta estuary was 105.7 mm, the growth coefficient (K)and Volta River, the growth performance index (Ø)´ ranged between 0.14–0.18 year−1 and Bivalvia 3.108–3.192, respectively. Total mortality (Z) was 0.65–0.82 year−1, while natural mortality (M) and fishing mortality (F) were 0.35–0.44 year−1 and 0.21–0.47 year−1, respectively, with an exploitation level of 0.32–0.57. The recruitment pattern suggested that G. paradoxa has year-round recruit- ment with a single pulse over an extended period (October–March) in the Volta River. The Volta River stock of G. paradoxa is overfished and requires immediate action to conserve it. This can be achieved by implementing a minimum landing size restriction and intensifying the culture of smaller clams which is a traditional activity at the estuary. RÉSUMÉ La dynamique des populations de palourdes d’eau douce Galatea paradoxa de la rivière Volta, Ghana Mots-clés : Les paramètres de population tels que (L∞) asymptotique, le coefficient de crois- recrutement, sance (K), les taux de mortalité (Z, F et M), le niveau d’exploitation (E)etlemodèle mortalité, de recrutement des palourdes d’eau douce Galatea paradoxa ont été estimés à paramètres l’aide des données de fréquences de longueur dans l’estuaire du fleuve Volta, au ∞ de croissance, Ghana. -