Highlights

Abstract

Keywords

1. Introduction

2. Methods

2.1. Review of literature

2.2. Online questionnaires

3. Results

3.1. Literature review results

3.2. Dictionary review results

3.3. Questionnaire results

3.4. Additional comments from stakeholder feedback

4. Discussion

5. Conclusion

Ethics statement

Declaration of Competing Interest

Acknowledgements

References

Abstract

‘Offshore’ aquaculture has gained increased attention as a potential route of expanding production of commercially important finfish species such as Atlantic salmon (Salmo salar). However, there is a lack of clarity about the term ‘offshore’ and how different ‘offshore’ environments are, compared to more traditional coastal or inshore locations. This uncertainty is an issue for effective governance and regulation and is a bottleneck for development that must be addressed. This study used a mixed method approach to evaluate what is meant by ‘offshore’ production and determine if existing approaches are suitable for licensing and regulating ‘offshore’ salmon aquaculture in Scotland, as a case study. First, a systematic literature review was used to assess academic studies and then an online questionnaire was used to gather views from salmon aquaculture stakeholders in Scotland and other countries. The results show there is inconsistency in what is perceived by the term ‘offshore’ aquaculture, making it challenging to determine a global definition. Literature, which was not limited to salmon production, tended to focus on distance from the coast but salmon aquaculture stakeholders had very mixed views, though a slight majority considered wave exposure was the key characteristic. The stakeholders indicated there may be a number of benefits of ‘offshore’ salmon aquaculture, but also suggested that existing regulations are not appropriate for ‘offshore’ salmon production and could be enhanced. The study results suggest that regulators and stakeholders need to agree on consistent terminology that characterises the production environment.

1. Introduction

Coastal regions are highly productive and an important resource for food production through aquaculture and fisheries. However, there is considerable competition and conflict from other users, so space for expansion of aquaculture is often limited (Sanchez-Jerez et al., 2016). Such constraints could affect contributions to global food supply as demand for aquatic products continues to rise (FAO, 2018). Thus, in many areas, if the aquaculture industry is to grow and increase production, there is a need to consider other locations. One of the alternatives to coastal farms is the use of so called ‘offshore’ sites, and consequently ‘offshore’ aquaculture has gained increased attention in recent years for both fish and shellfish (Jansen et al., 2016; Gentry et al., 2016; Barill´e et al., 2020). In 2010 the Food and Agricultural Organisation of the United Nations (FAO) held a workshop that classified mariculture into three categories based on site location (coastal, off the coast and offshore). The expert group defined mariculture as “offshore when it is located > 2 km or out of sight from the coast, in water depths > 50 m, with waves heights of 5 m or more, ocean swells, variable winds and strong ocean currents, in locations that are exposed (open sea, e.g. ≥ 180◦ open) and where there is a requirement for remote operations, automated feeding, and where remote monitoring of operating system may be required” (Lovatelli et al., 2013). This definition is prescriptive and consequently only relevant at present to few existing or exploited sites.

Highlights

Abstract

Keywords

1. The rationale and the early days

2. The glorious seventies – The birth of our family

3. From then onward

4. GnRHs – The basic and the applied

5. A few concluding thoughts

Acknowledgements

References

Abstract

Driven by the broad diversity of species and physiologies and by reproduction-related bottlenecks in aquaculture, the field of fish reproductive biology has rapidly grown over the last five decades. This review provides my perspective on the field during this period, integrating fundamental and applied developments and milestones. Our basic understanding of the brain-pituitary–gonadal axis led to overcoming the failure of farmed fish to ovulate and spawn in captivity, allowing us to close the fish life cycle and establish a predictable, year-round production of eggs. Dissecting the molecular and hormonal mechanisms associated with sex determination and differentiation drove technologies for producing better performing mono-sex and reproductively-sterile fish. The growing contingent of passionate fish biologists, together with the availability of innovative platforms such as transgenesis and gene editing, as well as new models such as the zebrafish and medaka, have generated many discoveries, also leading to new insights of reproductive biology in higher vertebrates including humans. Consequently, fish have now been widely accepted as vertebrate reproductive models. Perhaps the best testament of the progress in our discipline is demonstrated at the International Symposia on Reproductive Physiology of Fish (ISRPF), at which our scientific family has convened every four years since the grandfather of the field, the late Ronald Billard, organized the inaugural 1977 meeting in Paimpont, France. As the one person who has been fortunate enough to attend all of these meetings since their inception, I have witnessed first-hand the astounding evolution of our field as we capitalized on the molecular and biotechnological revolutions in the life sciences, which enabled us to provide a higher resolution of fish reproductive and endocrine processes, answer more questions, and dive into deeper comprehension. Undoubtedly, the next (five) decades will be similarly exciting as we continue to integrate physiology with genomics, basic and translational research, and the small fish models with the aquacultured species.

1. The rationale and the early days
Growing up I was fascinated by the sea, and I always wanted to be a marine biologist engaged in research that would explore ocean life to the benefit of society. Following this childhood passion, I studied biology as an undergraduate and in 1974 I enrolled in an Oceanography MSc program, both at the Hebrew University of Jerusalem. At that time, we already knew that the world was headed for a major fishery crisis, as overfishing was rampant and marine/coastal pollution was adversely impacting the spawning grounds of many marine species. When it was time to choose my Master’s thesis research topic, I decided to pursue marine aquaculture, which back then was in its infancy. The first bottleneck to be resolved in finfish aquaculture was the inability of many commercially important marine fish to reproduce reliably when raised in captivity. The budding mariculture industry had to rely on harvesting wild juvenile fish or broodstock, transporting them to the farming operation and growing them to harvest size (for juveniles) or stripping them to obtain eggs and sperm for the production of fertilized eggs, larvae and juveniles (for broodstock). These were, of course, very unreliable and unpredictable practices, as wild juveniles/broodstock were only available seasonally for a limited time, and in some years they could not be found at all. This led me (and several others in the field) to study fish reproductive biology and endocrinology, with the eventual goal of enabling predictable reproduction in captive fish and closing their life cycles. We hypothesized that fish do not reproduce in captivity because they do not experience the conditions of a spawning ground, and that the absence of these environmental conditions, which are difficult/impossible to simulate in captivity, causes a hormonal failure that is responsible for the lack of captive reproduction.

Decomposition of detritus plays a crucial role in the recycling of nutrients and organic matter (Swift et al. 1979; Moore et al. 2004). Defined as any resource of nonliving organic matter, detritus is considered the basal trophic level of many terrestrial and aquatic food webs (Swift et al. 1979; Moore et al. 2004; Benbow et al. 2015). In terrestrial ecosystems, detritus may consist of plant-derived matter (e.g. leaf litter, dead wood, root exudates), dead microbes, fecal matter and animal tissue (carrion) (Swift et al. 1979). Plantderived detritus comprises the majority of the resources that undergo decomposition in terrestrial ecosystems but they are nutrient poor and very recalcitrant (Swift et al. 1979; Carter et al. 2007). Contrary, carrion is much more nutrient-rich and decomposes at much faster rates than plant detritus, and, as such, its role in nutrient cycling may be highly relevant (Swift et al. 1979; Barton et al. 2013). Indeed, carrion decomposition is usually associated with the activity of microbes, invertebrate and vertebrate detritivores and scavengers (Carter et al. 2007; Barton et al. 2013). The combined activity of microbes and invertebrates increases the nutrients released from the carrion into the soil; however, vertebrates may reduce this contribution by direct consumption or dispersion (Carter et al. 2007; Barton et al. 2013). In terrestrial ecosystems where carrion releases nutrients into the soil, plants may ultimately mobilize these nutrients entering the belowground detrital pathway (Moore et al. 2004; Carter et al. 2007). Despite its potential importance, only very recently the scientific community has started to acknowledge the role of carrion decomposition in nutrient recycling (DeVault et al. 2003; Carter et al. 2007; Wilson and Wolkovich 2011). Detrital inputs enter any ecosystem via allochthonous or autochthonous sources (Moore et al. 2004). Allochthonous inputs are resources that originate in one habitat but move into another, while autochthonous inputs originate and are consumed in the same habitat (Polis et al. 1997). Many ecosystems experience spatial subsidies as regular seasonal events, but subsidies can also result from sporadic episodes of resource superabundance, named resource pulses (Ostfeld and Keesing 2000; Anderson et al. 2008b; Yang et al. 2008). Examples of resource pulses include periodical cicadas’ emergence in North American forests (e.g. Yang 2004, 2008), El Nin˜o rainfalls in arid ecosystems (e.g. Polis et al. 1997; Meserve et al. 2003; Letnic et al. 2005), seed or fruit mast events (e.g. Woff 1996; Curran and Leighton 2000), and massive spawning events by migratory fish (e.g. Woff and Hershey 1999; Yanai and Kochi 2005). Despite their ecological importance, these studies focused mostly on aboveground processes and just a few assessed belowground effects (Yang 2004; Yang et al. 2010).