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Three years after: What about Callista chione restoration plans

Three years after: What about Callista chione restoration plans . D. Del Piero*, M. Bolgan,* M. Burca,**, G. Calcagno,*S, D’Antoni,* C. Coglievina*, P. De Flego*, M. De Munari*,P. Diviacco***. * Life Science Dept, Trieste University Italy ** ICTP,OGS, Trieste Italy

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Three years after: What about Callista chione restoration plans

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  1. Three years after: What aboutCallista chione restoration plans D. Del Piero*, M. Bolgan,* M. Burca,**, G. Calcagno,*S, D’Antoni,* C. Coglievina*, P. De Flego*, M. De Munari*,P. Diviacco*** • * Life Science Dept, Trieste University Italy • ** ICTP,OGS, Trieste Italy • *** OGS DiamPros, Trieste Italy

  2. C. chione emerged as alternative fishery resource soon after the crisis of C. gallina (early 90’ties) • 21 fishery vessel,equipped with hydraulic dredges are involved in the exploitation in the FVG region • It’s still the most important clam resource in Northern Italy (as quantities landed, 961 mt in 2008) but the price it’s not very high • The fishery management is deserved to the local “Fishermen Consortium” and Producers Organisation (OP) • It’ seems a quite stupid mollusc • But it’s very interesting instead, because of the area covered • This is reflected on different growth performances in different areas

  3. The 2007 restocking plan In 2007 the fishermen decided the restocking of about 20 metric tons from a 20-22 m depth area to a “sanctuary” at 14-16 m depth The term “sanctuary” is referred to the limitation imposed to the fishery The challenge was to discover the effects of the restocking on the clams

  4. Area overview

  5. The fishermen Consortium, in agreement with OP implemented in his own district a policy of fishery restriction and experimental restocking activity, moving clams from a deeper area (20 –22 m depth) to a shallower one (14-16 m depth)

  6. Three years after • A survey was done in 2010 on the restocked area and the “new” and native clams were still recognizable. • Background: • a difference of three years was observed between clams of the same length sampled in the two zones, the deeper being apparently less favourable

  7. K-S test : D = 0.1598, Dalpha 0,05 =0,1888

  8. Slope test Length-AFWD after log transformation t = 3.215, 56 DF p< 0.01

  9. From survey done in 2010: • the cumulative frequency distributions aren’t significantly different • The Length-AFDW relationships instead suggest poorer performances in restocked clams • Benefits on recruitment were expected but till now are lacking • Dedicated plancton surveys are expected to clarify the larval journey, remembering that some density-dependent effect on settlement was discovered earlier

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