The loss of seed mussels in longline aquaculture

Abstract

Mussel aquaculture around the world is traditionally reliant on highly variable natural supplies of seed that are collected from the wild and transferred to mussel farms. [1][2][3][4][5][6][7] In many global regions, hatchery production is being increasingly used to provide a more consistent supply of seed mussels. However, the seeding of longline mussel aquaculture operations is inefficient, with many of the mussels from both wild and hatchery sources being lost in the first few months of aquaculture. [8][9][10] In many cases, losses can be extreme with >95% of seed being lost. [11][12][13] At seeding into longline aquaculture, loose mussels or seed attached to substrates, such as macroalgae, are deployed into the sea alongside a grow-out rope with a socking material holding the seed and their substrates in place. 7,14 The success of the seeding process is heavily reliant on survival of the seed mussels and their ability to migrate and attach to the grow-out rope. 9Losses of these seed mussels are a significant constraint to the continuity and envisaged growth of the global mussel farming industry 15 and represent a considerable waste of valuable natural resources or costly hatchery-reared seed. 16,17 Therefore, in the face of limited seed resources and the projected growth in human population and food demand, maximising production efficiencies to maintain or increase commercial mussel yield by mitigating against seed losses should be a fundamental goal of mussel aquaculture.

Settlement experiment of spat using three different collectors in two contrasting coastal sites from Chile (SE Pacific Ocean)

“…A. altra and C. chorus showed the highest settlement in summer at both sites. These results are in accordance with the spawning and settlement of mitilids, since temperature is the key driver underpinning these processes (South et al, 2021). Spawning seasons are spring and summer, with a prolonged larval development up to 45 days (Karayücel et al, 2003;Barria et al, 2012;Çelik et al, 2016).…”

Potential for Concentrated Microalgae as Replacement Diets for Juvenile Green-Lipped Mussels, Perna canaliculus

“…However, transferring early juvenile bivalves to grow-out in coastal farms, in an efort to reduce or eliminate the cost of nursery rearing, can result in high losses of the bivalves. For example, consistently high losses of greenlipped mussel spat have been reported in New Zealand within a few weeks after seeding of the spat onto coastal farms [3,46,47]. Replacing the costly production of live microalgae in spat nurseries by either full or partial substitution with more cost-efective replacement diets is therefore a pressing need [28,48].…”

“…Te suspended culture of mussels is normally reliant on seeding the farms with juvenile mussels, known as spat, which are most commonly harvested from the wild using a variety of techniques [1][2][3]. In New Zealand, an intermittent supply of juveniles or spat of the green-lipped mussel, Perna canaliculus, that are attached onto drifting seaweed that is washed ashore at Ninety Mile Beach has supplied around 70% of spat resource for all mussel farms in the country for at least 40 years [4][5][6].…”

Emersion and Relative Humidity Modulate Stress Response and Recovery Dynamics in Juvenile Mussels (Perna canaliculus)

“…Juvenile P. canaliculus are also routinely emersed to transfer them to sea-based nursery farms for aquaculture, a process that can take as long as 3 days and be highly variable in terms of environmental conditions [52]. Losses of juvenile P. canaliculus after they are seeded onto a marine farm are a common problem for the mussel industry in New Zealand, where most of the juveniles are lost during the first few months of aquaculture [53][54][55][56]. Based on the results of the present study, it is possible that conditions in which the juvenile mussels are transported trigger a series of molecular, biochemical and physiological responses in the mussels that could have carry-over effects for the mussels after seeding, potentially affecting retention and survival of the juveniles.…”