Three years after: What Three years after: What about about Callista chione Callista chione restoration restoration plans plans D. Del Piero*, M. Bolgan,* M. D. Del Piero*, M. Bolgan,* M. Burca,**, G. Calcagno,*S, Burca,**, G. Calcagno,*S, D’Antoni,* C. Coglievina*, P. D’Antoni,* C. Coglievina*, P. De Flego*, M. De Munari*,P. De Flego*, M. De Munari*,P. Diviacco*** Diviacco*** Life Science Dept, Trieste University Italy * ICTP,OGS, Trieste Italy ** OGS DiamPros, Trieste Italy
10
Embed
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 - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Three years after: What aboutThree years after: What aboutCallista chioneCallista chione restoration plans restoration plans
D. Del Piero*, M. Bolgan,* M. Burca,**, G. D. Del Piero*, M. Bolgan,* M. Burca,**, G. Calcagno,*S, D’Antoni,* C. Coglievina*, P. Calcagno,*S, D’Antoni,* C. Coglievina*, P. De Flego*, M. De Munari*,P. Diviacco***De Flego*, M. De Munari*,P. Diviacco***
•* Life Science Dept, Trieste University Italy•** ICTP,OGS, Trieste Italy•*** OGS DiamPros, Trieste Italy
C. chione C. chione emerged as alternative fishery resource soon after emerged as alternative fishery resource soon after the crisis of the crisis of C. gallina C. gallina (early 90’ties)(early 90’ties)
21 fishery vessel,equipped with hydraulic dredges are 21 fishery vessel,equipped with hydraulic dredges are involved in the exploitation in the FVG regioninvolved in the exploitation in the FVG region
It’s still the most important clam resource in Northern Italy It’s still the most important clam resource in Northern Italy (as quantities landed, 961 mt in 2008) but the price it’s not (as quantities landed, 961 mt in 2008) but the price it’s not very highvery high
The fishery management is deserved to the local “Fishermen The fishery management is deserved to the local “Fishermen Consortium” and Producers Organisation (OP) Consortium” and Producers Organisation (OP)
It’ seems a quite stupid molluscIt’ seems a quite stupid mollusc But it’s very interesting instead, because of the area coveredBut it’s very interesting instead, because of the area covered This is reflected on different growth performances in different This is reflected on different growth performances in different
areasareas
The 2007 restocking planThe 2007 restocking plan In 2007 the fishermen decided the restocking of about 20 In 2007 the fishermen decided the restocking of about 20
metric tons from a 20-22 m depth area to a “sanctuary” at metric tons from a 20-22 m depth area to a “sanctuary” at 14-16 m depth14-16 m depth
The term “sanctuary” is referred to the limitation imposed to The term “sanctuary” is referred to the limitation imposed to the fisherythe fishery
The challenge was to discover the effects of the restocking The challenge was to discover the effects of the restocking on the clamson the clams
Area overview
The fishermen Consortium, in agreement The fishermen Consortium, in agreement with OP implemented in his own district a with OP implemented in his own district a policy of fishery restriction and experimental policy of fishery restriction and experimental restocking activity, moving clams from a restocking activity, moving clams from a deeper area (20 –22 m depth) to a shallower deeper area (20 –22 m depth) to a shallower one (14-16 m depth) one (14-16 m depth)
Three years afterThree years after
A survey was done in 2010 on the A survey was done in 2010 on the restocked area and the “new” and native restocked area and the “new” and native clams were still recognizable.clams were still recognizable.
Background:Background: a difference of three years was observed a difference of three years was observed
between clams of the same length sampled between clams of the same length sampled in the two zones, the deeper being in the two zones, the deeper being apparently less favourableapparently less favourable
K-S test : D = 0.1598, Dalpha 0,05 =0,1888
sample 25-26
0
0,2
0,4
0,6
0,8
1
3 4 5 6 7 8 9
length (cm)
% c
um. F
req.
sample 25
sample 26
y = 3,0136x - 4,9148R2 = 0,9617
y = 3,3107x - 5,3516R2 = 0,9517
-1,5
-1
-0,5
0
0,5
1
1,5
1 1,2 1,4 1,6 1,8 2 2,2
2526Length-AFDW 25Length-AFDW 26
Slope test
Length-AFWD after log transformation t = 3.215, 56 DF p< 0.01
From survey done in 2010:From survey done in 2010: the cumulative frequency distributions aren’t significantly the cumulative frequency distributions aren’t significantly
differentdifferent The Length-AFDW relationships instead suggest poorer The Length-AFDW relationships instead suggest poorer
performances in restocked clamsperformances in restocked clams Benefits on recruitment were expected but till now are Benefits on recruitment were expected but till now are
lackinglacking Dedicated plancton surveys are expected to clarify the Dedicated plancton surveys are expected to clarify the
larval journey, remembering that some density-dependent larval journey, remembering that some density-dependent effect on settlement was discovered earliereffect on settlement was discovered earlier