Growing seed mussels (spat) to larger sizes in single‐seed nursery culture systems prior to seeding onto coastal mussel farms is an effective approach for greatly reducing costly spat losses during ...this stage of mussel aquaculture. However, the production of single‐seed mussel spat in nursery culture systems relies on first separating spat from the settlement substrata to which they are attached, whether spat are settled in a hatchery or gathered from the wild. This study sought to determine whether chlorination could be an effective approach for separating wild Greenshell mussel (Perna canaliculus) spat from beachcast macroalgal material (Kaitaia spat material) harvested from a beach in northern New Zealand. The results demonstrate that chlorination (i.e. in solutions of up to 0.625% sodium hypochlorite) is a highly effective approach for separating spat, resulting in the detachment of up to 94.6% in one treatment without increasing mortality relative to controls. The effectiveness of chlorination was modulated by spat density, with increasing spat densities, lowering rates of detachment. While chlorination is effective at separating small spat (i.e. successfully separating 72.4% of spat <750 μm in shell length) overall spat densities, further investigation is required to determine how to effectively separate larger spat (i.e. with chlorination only successfully separating 21.5% of spat >750 μm). The high survival (relative to the control treatments) also suggests that chlorine concentrations and exposure durations could be increased from those used in this study. These results demonstrate that chlorination can be used to separate spat from substrate prior to their transfer to nursery systems for ongrowing, paving the way for such approaches for reducing spat losses to be integrated into the aquaculture production cycle.
This study sought to determine whether chlorination could be used as an effective approach for separating seed mussels (Perna canaliculus) from macroalgae. The results demonstrate that chlorination can be used as an effective approach for separating seed mussels from macroalgae, without resulting in increased mortality.
Large-scale losses of spat are commonplace during the early stages of mussel aquaculture costing the industry millions in lost production. The dominant cause of this poor spat retention is thought to ...be secondary settlement behavior, whereby spat detach from farming substrata in an effort to relocate to another site. One approach that could be used to reduce these spat losses is to use natural substrates, such as macroalgae, to which wild mussel spat commonly attach. These natural substrates are often associated with chemical and morphological settlement cues. In New Zealand, the majority of mussel spat used by the aquaculture industry are harvested from the wild while attached to a range of species of macroalgae and other general debris (referred to as Kaitaia spat material). The filamentous morphology and chemicals released by some of these macroalgal species, including the rhodophyte
Pterocladia lucida
, have been shown to improve mussel settlement. Therefore, in this study, the spat of the green-lipped mussel,
Perna canaliculus
, were seeded onto aquaculture grow ropes with and without
P. lucida
to determine whether the presence of the macroalgae would improve the retention of the mussel spat. The presence of
P. lucida
increased spat retention by 33% relative to a control over 12 weeks and also increased the proportion of spat (by 16%) that successfully migrated away from biodegradable seeding substrata onto the permanent structure of the grow rope. The timing of spat losses relative to the breakdown of seeding substrata is consistent with the macroalga producing chemical cues that encourage spat settlement. In contrast, no spat attached directly to the
P. lucida
suggesting morphology of the macroalga was not playing a role in the observed increase in spat retention. These results suggest that there may be chemical cues present in
P. lucida
that may have the potential to be used to help resolve the problem of poor spat retention in green-lipped mussel aquaculture.
Major losses of early juvenile seed mussels or spat are a typical feature of the aquaculture production cycle for many mussel species. These losses are caused by a variety of factors including ...predation, mortality, and the innate migratory behaviour of spat. In this study, we examined the potential to reduce spat losses by using a floating upwelling system (FLUPSY) for raising the spat of New Zealand's Greenshell™ mussel (Perna canaliculus) to a larger size before transfer to a coastal mussel farm. The losses of spat experimentally cultured within a FLUPSY over 85 days were much lower compared to spat that were seeded directly into coastal waters (78% vs. 99.8%). At the end of the 85‐day nursery culture period, spat in the FLUPSY were 7% larger despite being cultured at higher densities. The losses for two size classes of spat that were raised in the FLUPSY remained relatively high (83% and 95% for spat seeded out at 6.6‐ and 15.5‐mm shell length (SL) respectively) after two months of being experimentally seeded onto a coastal mussel farm. However, these losses are lower than have been reported previously for this species during this stage of production. The results from this study suggest that the addition of a FLUPSY nursery stage to the Greenshell™ mussel production could greatly reduce spat losses and improve production efficiency.
The seeding of small juvenile green‐lipped mussels (Perna canaliculus) onto coastal farms is associated with high losses. These losses can be reduced by seeding larger juveniles; however, the nursery ...culture of juveniles is unviable because of the high cost of producing live microalgal feeds. In this study, we compared the ability for two diets, a formulated microparticulate feed, MySpat and liposomes fabricated with mussel extract to replace live microalgae at different proportions for feeding small (1.9 mm shell length ±0.02 SE) green‐lipped mussels. The experimental diets consisted of a mix of live Tisochrysis lutea, Diacronema lutheri and Chaetoceros muelleri that were replaced with increasing proportions of MySpat (25%, 50% and 75%), and liposomes (25% and 50%). There were no significant differences in mortality of mussels relative to the control (100% microalgae) among any of the diet treatments. However, mussel growth tended to decrease with increasing substitution of the microalgal component of the diets. The results from this study suggest that microparticulate and liposome formats provide a viable mode of food delivery to juvenile mussels, with improved formulation of these formats having the potential to lead to the substitution of live microalgal diets which make nursery culture unviable at present.
The loss of seed mussels in longline aquaculture South, Paul M.; Delorme, Natalí J.; Skelton, Bradley M. ...
Reviews in aquaculture,
January 2022, 2022-01-00, 20220101, Letnik:
14, Številka:
1
Journal Article
Recenzirano
The substantial loss of seed mussels during the early stages of longline aquaculture—often exceeding 95%—is a major issue that erodes the security and profitability of production while limiting the ...sustainable expansion of this industry in many parts of the world. There are many biological, environmental and procedural factors that potentially cause seed losses. The present understanding of these factors is highly limited, based on disparate lines of evidence and constrained by the challenges associated with quantifying the fate of minute organisms in the field. Addressing these knowledge gaps is a prerequisite for meeting the growing global demand for farmed seafood and requires significant and coherent research. We identify the diverse range of potential drivers of seed loss in mussel aquaculture and review existing knowledge around these factors to identify critical knowledge gaps and research priorities. Losses appear to be caused by a complex suite of interacting factors that include stress during transfer between regions, underlying variations in seed condition, change in the farm environment, predation, competition from biofouling organisms and migratory behaviour of seed mussels. Solutions to the losses of mussel seed in commercial culture are mostly likely to be achieved through research directed at evaluating a range of practical interventions during the critical phase of nursery culture of mussel seed.
The nutritional condition of seed mussels (spat) at the time of seeding is thought to play a major role in influencing spat losses on mussel farms, with nutritionally compromised spat thought to be ...more likely to be lost from aquaculture substrata than those in good condition. New Zealand's Greenshell™ mussel (Perna canaliculus) aquaculture industry relies almost exclusively (∼85%) on wild caught spat, with the vast majority, typically > 90%, lost shortly after being seeded onto coastal mussel farms. This study sought to quantify the extent of the variability in the nutritional condition (i.e., calorific, protein, lipid and carbohydrate content) of samples of spat used by the Greenshell™ industry between 2014 and 2021 (i.e., wild caught and hatchery produced) as a first step towards determining whether variability in nutritional condition may be a significant contributor to the marked variation observed in spat performance after it is seeded onto coastal farms. All parameters measured were highly variable among wild spat samples, with all but lipid content varying, including for samples of wild spat harvested at different times within the same month. Furthermore, there were no clear patterns in the nutritional condition of spat across months or years, suggesting environmental factors that limit feeding during the harvest and transport of spat may be contributing to marked differences in the quality of spat being used by the industry to seed farms. These results provide a baseline for assessing the nutritional condition of Greenshell™ spat and point towards a need to develop interventions to improve the quality of wild spat supply for this industry to help and prevent the ongoing massive losses of spat from farms. These measures could include, testing nutritional condition of spat at harvest or prior to seeding, development of nursery culture methods and development of artificial spat feeds that have the potential to replace live phytoplankton during nursery culture.
The early stages of mussel aquaculture can be extremely inefficient, with the majority of seed mussels often lost shortly after seeding out onto coastal farm structures. These high losses of seed ...mussels (conversely known as poor spat retention) are extremely costly to the mussel aquaculture industry, while constraining production and the growth of the industry. The causes of poor spat retention are unclear, though it appears to be predominantly caused by secondary settlement behaviour, which is a process which enables juveniles to actively settle and resettle among a variety of settlement substrata. One factor that appears to play an important role in the settlement of a range of commercially important mussel species is the physical complexity of settlement substrata. Smaller seed mussels settle preferentially onto finely branching filamentous substrata, whereas larger seed mussels prefer coarser substrates. In this study the seed of the green-lipped mussel, Perna canaliculus, were seeded onto grow ropes with a range of physical characteristics to determine whether modifying the structure of seeding materials could improve seed mussel retention. Modifying the physical characteristics of seeding substrata had no impact on mussel retention; with high losses observed from grow ropes in each treatment. Seed mussels were highly mobile following seeding out and rapidly began to migrate among seeding substrata. The majority of seed losses occurred while these small-scale migrations were taking place, suggesting these movements maybe a major contributor to the loss of seed mussels from farms. These results suggest new approaches for seeding out mussels that do not require small-scale migrations of mussels between substrata should be developed and tested.
•Spat losses were compared among dropper ropes with varying degrees of physical complexity•Spat retention was poor, with less than 1% of initial seeding densities remaining on droppers in each treatment after 106 days•Modifications to the physical structure of grow ropes do not appear to influence mussel spat secondary settlement
High losses of seed mussels (spat) during the early stages of mussel aquaculture is a major problem that results in the inefficient use of spat, which severely disrupts production and ultimately ...constrains industry growth. These losses are thought to be caused by a variety of factors including predation, mortality, the natural migratory behaviour of mussel spat and inappropriate culture conditions, such as excessive seeding density. Mussel farmers frequently seed out with high densities of spat in anticipation of the subsequent losses of spat. In this study, we measured the impact of three different seeding densities on nursery dropper rope (low – 11,782 spat m−1, medium – 17,640 spat m−1, and high – 59,242 spat m−1) on subsequent spat losses on two Greenshell™ mussel (Perna canaliculus) farms in New Zealand. Seeding out at the high and medium initial seeding densities resulted in greater spat losses (93.5% and 90.0%, respectively) over 59 days compared with the low initial density (49.5%). Furthermore, despite the significant differences in initial seeding densities among the three treatments, similar numbers of spat (i.e., ~ 3000 spat m−1) remained on dropper ropes in each treatment at the two farm sites after 59 days. Growth of spat over 59 days did not appear to be affected by initial seeding density that might otherwise be expected if there was competition for resources (e.g., space and food) associated with the experimental densities. These results suggest that the optimal seeding density of spat on Greenshell™ farms may be much lower than current seeding densities, and that farmers may be able to significantly improve spat retention and the efficiency of the use of spat by simply reducing their seeding densities.
•Spat losses were compared among droppers seeded at three seeding densities.•Spat losses were high, and increased with increasing seeding density.•Seeding out at considerably lower seeding densities may be an effective approach to reduce losses on Greenshell™ farms.
The inefficient conversion of seed mussels, or ‘spat’ into market-ready mussels is a major problem for mussel aquaculture operations worldwide, where sustained crop losses throughout the production ...cycle severely disrupt production and ultimately constrain industry growth. However, despite the severity of the problem for individual mussel farm operators, few studies have sought to examine this inefficiency on an industry-wide scale to assess the broader extent of the biological and economic losses. The Greenshell™ mussel (Perna canaliculus) industry is New Zealand's largest and most valuable aquaculture industry, and yet despite its success, the industry remains extremely inefficient at converting spat into market-ready adult mussels. Consequently, this study compiled and compared historical industry-wide data on the harvesting of spat with national statistics on the production of adult mussels by the aquaculture industry. The results of the analyses show that despite substantial increases in the harvesting of wild spat over the last 10 years, the production of market-ready mussels from the industry has not increased concordantly, remaining largely static at around 90,000 t, amounting to around 1.78 billion adults a year during this period. From 2015 to 2020 on average, 344 billion spat were harvested from the wild each year, yet <1% of these were retained on Greenshell™ farms from seeding out through to final harvest. Careful evaluation of historical data reveals the efficiency of converting seeded Greenshell™ spat to harvested market-ready mussels has halved over the last 30 years, with the cause of this marked decline uncertain. These results highlight the inefficient nature of the Greenshell™ industry and show that improving production efficiency by even a small margin would result in substantial production gains for the industry.
•Mussel aquaculture operations across the world are extremely inefficient at converting seed mussels into market-ready adults•Greenshell™ production has remained largely static over the past few years despite increasing spat harvests•344 billion spat are harvested each year, but <1% of these are retained on farms from seeding through to final harvest•Improving efficiency by even a small percentage would produce substantial gains for industry
The early stages of mussel aquaculture can be extremely inefficient, with large numbers of seed mussels, also known as spat, lost from production shortly after seeding out. The exact causes of these ...losses are unclear, although factors such as local environmental conditions at farm sites, fish predation, mortality and the secondary settlement behaviour of spat are likely to play a role. Spat losses are an acute problem for Greenshell™ mussel (Perna canaliculus) aquaculture in New Zealand, where up to 100% of spat can be lost within a few months of seeding onto coastal farms. However, the timing and pattern of spat losses on Greenshell™ farms has not been well documented. This study aimed to quantify spat losses to determine if they occur consistently at individual locations at different times of the year, or if they vary among spat from different sources (i.e., Kaitaia and line-caught spat). Wild spat harvested from two sources were seeded onto commercial Greenshell™ mussel farms in four experiments, which measured their subsequent performance over 3 months, while also measuring a range of environmental conditions for comparison. Spat losses were considerable (frequently in excess of 70%) and occurred early in the production cycle (within the first month following seeding out). Local environmental conditions appeared to play a minimal role in influencing secondary settlement behaviour, as spat retention varied little among individual farm sites, and between experiments conducted at different times of the year. However, the movement of spat among the substrata used for seeding spat suggests that improvements in spat retention may come from altering the arrangements for deploying spat to mussel farms, such as seeding out with larger, single seed spat.
•This study measured the retention of spat seeded onto coastal Greenshell™ farms in New Zealand.•Spat retention was poor, reaching <1% when seeding out with Kaitaia spat, and 21% when seeding with line caught spat.•Spat losses were consistent among farm sites, between spat sources, and time of the year.
