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Add To Calendar 24/02/2016 11:15:0024/02/2016 11:35:00America/ChicagoAquaculture 2016ENERGETICS PARAMETERS APPLIED TO FAMILY SELECTION IN A GREENSHELL MUSSEL, Perna canaliculus, BREEDING PROGRAMME   LoireThe World Aquaculture Societyjohnc@was.orgfalseanrl65yqlzh3g1q0dme13067DD/MM/YYYY

ENERGETICS PARAMETERS APPLIED TO FAMILY SELECTION IN A GREENSHELL MUSSEL, Perna canaliculus, BREEDING PROGRAMME  

Norman L. C. Ragg*, Zoë Hilton, Ellie Watts, Jolene Taylor, Jonathan Morrish, Kevin Heasman and Nick King
 
Aquaculture Group - Cawthron Institute
Private Bag 2, Nelson 7042
New Zealand
norman.ragg@cawthron.org.nz

The Greenshell™ mussel (Perna canaliculus) aquaculture industry generates approximately $200M USD p.a. in export revenue for New Zealand. Until recently the industry was entirely dependent upon the on-growing of wild spat; however the Cawthron Institute has now developed a selective breeding programme, leading to the establishment of New Zealand's first commercial mussel hatchery. Over 6 generations the breeding programme has focused on bulk production traits, achieving sustained improvements in growth and meat yield. However, the physiological characteristics underpinning faster growth remain unclear. Farmers have expressed a desire to avoid greedy and inefficient mussels that, while supporting accelerated individual growth rates, may ultimately reduce the net carrying capacity of a farm. As coastal aquaculture space becomes increasingly limited, there is also interest in the exploitation of low seston 'blue water' sites. The present trial therefore aimed to establish energy budgets for all 43 families created in the 2012 breeding cohort, characterising performance efficiencies in marginal food environments. Fourteen month-old sub-adult mussels were incubated in tanks receiving a controlled diet of Isochrysis galbana + Chaetoceros calcitrans (1:1 cell ratio, 30 cells µL-1) for 3-5 months. The 5-17g live weight mussels were grouped into triplicate mesh bags of 15 individuals. On a pre-assigned terminal sampling day, each bag was transferred to a flow-through respirometer to allow oxygen consumption (standard metabolic rate, SMR), defaecation, particle clearance and ammonia excretion to be quantified before sacrificing the animals to establish proximate composition and dry mass. Instantaneous performance and efficiency was determined by applying a simple Scope for Growth model:

SFG = C - (F + R + E)            

Representing energy gain by feeding (C), or lost in faeces (F), ammonia excretion (E) or standard metabolism (R). The feed treatment appeared nutritionally inadequate, resulting in low or negative SFG. However the treatments successfully produced a range of distinct family SFG, ranging from -222 to +58 J g dry tissue-1 d-1. Ingestion rates were surprisingly constant across all families (mean ± SEM: 122 ± 5 J g-1 d-1), as was standard metabolic rate (90 ± 3 J g-1 d-1). Ammonia excretion only represented a minor contribution to SFG (8 - 32 J g-1 d-1). The great majority of SFG variability was driven by faecal losses, which closely matched ingestion in families with lower SFG, but declined to 12-54% of ingested energy in high SFG families. Absorption efficiency therefore appears to be the key driver of SFG variability between families. These findings were corroborated by a parallel trial, where mussels received a natural pond-cultured phytoplankton assemblage (~35 particles µL-1, 70% organic matter). The results suggest feeding performance can be manipulated within a breeding programme, warranting further method optimisation for high throughput screening and examination of commercial implications.

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