105

seeks to reduce the number ! fish that escape "om European aquaculture through research to improve fish farming techniques and technologies.

PREVENT ESCAPE is financially supported by the Commission of the European Communities, under the 7th Research Framework Program.

www.preventescape.eu

authors: Pablo Sanchez-Jerez1, Pablo Arechavala-Lopez1, Damian Fernandez-Jover1, Ingebrigt Uglem2, Kenny Black3, Stelios Somarakis4, Manolis Ladoukakis5, Ricardo Haroun6, Tim Dempster7

1 University of Alicante, Spain2 Norwegian Institute of Nature Research, Norway3 Scottish Association of Marine Science, Scotland4 Hellenic Centre of Marine Research, Crete, Greece5 University of Crete, Crete, Greece6 University of Las Palmas de Gran Canarias, Spain7 SINTEF Fisheries & Aquaculture, Norway

4.1. THE IMPORTANCE OF IDENTIFYING ESCAPED FISH FROM AQUACULTURE AND DETERMINING THEIR POST-ESCAPE BEHAVIOURS FOR ENVIRONMENTAL AND FISHERIES MANAGEMENTCite this article as: Sanchez-Jerez P, Arechavala-Lopez P, Fernandez-Jover D, Uglem I, Black K, Somarakis S, Ladoukakis M, Haroun R & Dempster T (2013) The importance of identifying escaped fish from aquaculture and determining their post-escape behaviours for environmental and fisheries management. In: PREVENT ESCAPE Project Compendium. Chapter 4.1. Commission of the European Communities, 7th Research Framework Program. www.preventescape.eu

ISBN: 978-82-14-05565-8

106

Farmed fish may differ both in morphology and condition from wild fish, which likely affects their behaviour, competitive ability and spawning success compared with wild populations. These changes to biological characteristics are both environmental, due to the conditions of the culture, and genetic in origin. Escapes have been documented for almost all of the main species produced along European coastlines, such as Atlantic salmon (Salmon salar), Atlantic cod (Gadus morhua), seabass (Dichentrarchus labrax), seabream (Sparus aurata) and meagre (Argyrosomus regius). Escapes have the potential to mix with wild populations and negatively affect survival and fitness (Chapter 4.3).

After an escape event, farmed fish may swim to natural habitats and mix with wild stocks. If this takes place on feeding grounds and the escapees compete for food resources used by wild fish, the availability of food may decrease, particularly if the carrying capacity of the ecosystem is near its upper limit. In some cases, cannibalism can be also an important impact, with increasing mortality of young individuals through predation by escapees. Reproduction of wild fish populations can also be affected if escapes can spawn successfully in areas where wild conspecifics exist, resulting in interbreeding. After successful interbreeding, the behavioural and life history characteristics of the resulting wild-farmed hybrids may be altered, potentially reducing their performance in the wild. Therefore, invasions of escaped farmed fish have the potential to negatively impact the productivity of wild fish populations through resource competition and competitive displacement. While the outcome of interactions between farm and wild fish will be context-dependent, varying with a number of environmental and genetic factors, they will frequently be negative for wild fish (Thorstad et al. 2008).

For fisheries biology, the analysis of population structure for a species is of primary importance in developing an optimal strategy for efficient management. Distinguishing escapees from natural individuals can be of great importance in this context. In addition to distinguishing between wild and farmed fish, determining the spatial distribution of escapees in wild populations and the movements and migratory patterns of escapees when they reach natural environments is clearly important. For example, measures of growth, survival and reproductive success all assume that a single wild population is being studied. Population mixing with escapees confounds such measures, introducing noise into assessments of wild populations. In areas where aquaculture is intensively practiced, managers must

NATURAL FISH POPULATIONS MIXED WITH ESCAPEES FROM AQUACULTURE: HOW CAN WE DETECT THE ESCAPEES?

The “Post-escape” work package aimed to develop efficient methods to identify escaped Atlantic cod, seabream, seabass and meagre based on analyses of morphological variation, growth patterns in scales and otoliths, trace element profiles of scales, tissue fatty acid profiles, and genetic indicators. Further, the work package determined the immediate post-escape behaviour and the long-term spatiotemporal distribution of escapees from fish farms to assess the prospects and develop optimal protocols for recapture of escapees. The work package also evaluated the ecological functions of escapees and assessed the impact of escapees on local professional and recreational fisheries.

Fisheries biology has developed different approaches to identify and classify fish stocks, because understanding stock structure is vital to design appropriate management regulations in fisheries (Begg and Waldman 1999). Based on this principle, escapees can be treated as a specific stock within a species, with particular features that can be used for clear distinction from wild congeners.

OBJECTIVES OF THE “POST-ESCAPE” WORK PACKAGE.

HOW CAN ESCAPEES BE IDENTIFIED?

Morphological changes

include the “immigration” and potential establishment of escaped congeners in their decision-making. Therefore, they need information on the abundance, size structure, reproductive success, trophic behaviour and spatial distribution of both wild and escaped populations. For this purpose, managers need to know the biological differences between escapees and wild populations, and they will need tested tools for identifying intraspecific units or stocks of a species to enable better management.

107www.preventescape.eu

In hatcheries, fish grow faster and experience a different environment than their wild counterparts. This phenomenon has been utilized to distinguish between wild and reared salmonids with a relatively high degree of certainty (Fleming et al. 1994, Fiske et al. 2005). Differential relative growth of body parts conditioned by environmental factors is a common feature of fish development (Osse and van den Boogaart 1995, Loy et al. 1999). In several

108

Elemental signatures contained in some body elements, such as otoliths or scales, reflects the exposure of an individual fish to both the environment and its own physiology. These signatures typically differ among groups of fish, which have experienced different environmental histories, whether or not the groups come from the same population (Campana 2005). The presence of different signatures can be used to infer the existence of groups of fish that have remained separate for a certain period of time. The presence of variations in water temperature and chemistry inside fish farms can result in different otolith and scale chemical composition, and suggests that elemental fingerprints should discriminate well among escapees and wild fish (Campana et al. 2000).

Changes to otolith and scales elemental composition

Aquaculture feeds have a very specific formulation with respect to their fatty acid constituents, with terrestrial vegetable oils and meals now heavily used to replace oils and meals derived from marine fish sources. Much research has focused on determining the optimal proportions for the substitution of fish meal and fish oil by plant products, without compromising fish growth or health (Turchini et al. 2009). However, vegetable oils, such as soybean, rapeseed, linseed, or palm oils, cause a distinct change in the fatty acid profile of aquacultured fish away from their wild counterparts. This is because aquafeeds are rich in saturated acids such as palmitic (16:0) or stearic acid (18:0), monounsaturated fatty acids such as oleic acid (18:1n-9), and polyunsaturated fatty acids (PUFA), especially linoleic acid (18:2n-6). Fatty acids are not inert compounds. They accumulate over time and represent an integration of dietary intake over days, weeks, or months, depending on the organism and its energy intake and storage rates (Iverson 2009). Fatty acids have often been used as dietary markers (Iverson et al. 2004) and can be applied for monitoring the influence of fish farming on the environment (Fernandez-Jover et al. 2011), because changes in the fatty acid composition can be easily and unequivocally identified in fish tissues.

Fatty acid profiles as biomarkers

species, developmental modifications may also be closely linked to ontogenetic changes in resource use (Sagnes et al. 1997, Ward-Campbell and Beamish 2005). Such different developmental modifications may exist between wild and farmed fish given that they experience large differences in feeding regime and environment. For example, farmed fish are fed on feed pellets and confined to fish cages.

Geometric analysis of scales and otoliths provide sources of variation amenable to morphometric and other forms of analysis (e.g. Richards and Esteves 1997). Features containing stock-specific information such as annuli spacing are biologically interpretable (i.e. related to age and growth), whereas other features such as perimeter shape are not easily interpretable (Begg and Waldman 1999).

The strength of genetic differences among stocks is positively associated with time since divergence of stocks (mediated by generation time, with shorter generation time accelerating genetic differentiation), and their degree of isolation (i.e., reproductive exchange between stocks eroding genetic differences, Adkinson 1996). Fish aquaculture uses wild caught broodstock from different regions, which can result in immediate differences between wild and farmed fish. In addition, the selective breeding of aquaculture fish currently underway for many species will increase divergence between farmed and wild populations. Therefore, the potential for detectable genetic differences between farmed and wild stocks is high. Some loss of genetic diversity, in comparison with wild stocks, had been reported in farmed stock, probably arising from genetic drift. The scale of genetic differences could be used as a precise tool to discriminate escapees.

Farmed fish are confined in a reduced water volume, with typical densities ranging from 5 to 25 kg m-3. When an escape event occurs through storm-induced damage or human error (Chapter 2.2), escapees can move freely around the farm structure or migrate to natural habitats. Understanding the movements and dispersal of escapees at scales of days to years after an escape event is important to management and conservation of natural resources in numerous ways (Metcalfe et al. 2008), although obtaining the necessary information is frequently difficult. It is only by understanding the movements and behaviour of individuals over short (hour-days), medium (days-weeks) and long (seasons and years) time-scales that managers can reveal the potential to recapture escapees and determine how escapees use natural resources such as food and compete with wild congenerics. Therefore, in the Post-escape work package, we studied fish movements with a focus on determining practical, implementable management options.

Mixed behavioural strategies within species and populations (Dingle 1996), selection pressure imposed by fishing (Law 2000) and predators (Sanchez-Jerez et al. 2008), and differences in habitat suitability and oceanographic conditions result in large variations in the spatial distribution in a region where an escape event has happened. Detailed knowledge of the movement behaviour of a fish species is required to decide which proportion of suitable habitat needs to be protected to positively affect the exploited stock and to quantify this effect to provide a convincing argument for the closure of an area to fishing.

Genetic tools

ESCAPEES IN THE WILD: WHERE DO THEY GO?

109www.preventescape.eu

Direct underwater observation of escapes could detect specific interactions between escapees and wild pelagic and benthic fish, but only over a short-time scale (e.g. predation, cage re-entering behaviour, schooling with wild population, the use of shelter). For studies longer than the scale of hours, tagging methods that involve marking the fish with a marker (e.g. plastic tag) that allows the identification of the fish either visually or with the aid of a detection device are required (Dempster and Kinsgford 2003). Commercial or sport fisheries can also recapture tagged fish. Mark and recapture is widely used in the study of dramatic, large-scale, often transoceanic, movement patterns of commercially valuable species. However, mark and recapture data are of limited value when used to predict home range behaviour, as they typically contain only two positions occupied during the life of a fish. Thus, the spatial resolution in such studies is too coarse to quantify the use of space accurately (Kerwath 2005).

Attaching an acoustic transmitter capable of emitting a signal that can be recorded by a passive acoustic receiver is an alternate technique (Uglem et al. 2009, Arechavala-Lopez et al. 2010). Acoustic telemetry techniques enable the tracking of small-scale movements of marine fishes, because the presence and depth of a tagged fish can be recorded through an array of receivers. Continuous tracking of escapees for extended time periods is therefore possible.

The process of detecting escapees from aquaculture is essential for effective fisheries management and to promote mitigation actions. Methods to detect Atlantic salmon escapees are largely established (e.g. Glover et al. 2010), but the development of new tools and technologies to discriminate escapees continues. The most optimal indicator(s) for distinguishing escaped Atlantic cod, seabass, seabream or meagre was poorly described prior to the Prevent Escape project. Further, knowledge regarding their post-escape behaviours was lacking, making assessments of whether to invest time and resources in recapture efforts and how to undertake recapture without a knowledge basis. The following chapters (Chapter 4.2 — 4.7, this compendium) detail the indicators that can be used to distinguish escapees and wild fish of these species and document their behaviour once they enter the natural environment as escapees, with the principal aim to develop optimal strategies to detect and mitigate the environmental effects of escapees.

CONCLUSIONS

110

www.preventescape.eu 111

Figure 4.1.1. Example of a mistakenly labelled wild fish: farmed escaped

gilthead seabream labelled and priced as wild fish in a Spanish fish market.

Figure 4.1.2. A single hole in the net can lead to escapes of fish from aquaculture.

Tracking the movement of fish after an escape can provide information to

organize recapture efforts.

112

Adkinson MD (1996) Population differentiation in Pacific salmon: local adaptation, genetic drift, or the environment. Can J Fish Aquat Sci 52: 2762-2777

Arechavala-Lopez P, Uglem I, Sanchez-Jerez P, Fernandez-Jover D, Bayle-Sempere JT, Nilsen R (2010) Movements of grey mullet Liza aurata and Chelon labrosus associated with coastal fish farms in the western Mediterranean Sea. Aquacult Environ Interact 1: 127-136

Begg GA, Waldman JR (1999) An holistic approach to fish stock identification. Fish Res 43: 35-44

Campana SE (2005) Otolith elemental composition as a natural marker of fish stocks. In: Stock identification methods. Application in Fishery Science. Ed: Cadrin SX, Friedlan, KD, Waldman, JR, Elsevier

Campana SE, Chouinard GA, Hanson M, Fréchet A, Brattey J (2000) Otolith elemental fingerprints as biological tracers of fish stocks. Fish Res 46: 343-357

Dempster T, Kingsford MJ (2003) Attraction of pelagic fishes to fish aggregation devices (FADs): the role of sensory cues. Mar Ecol Prog Ser 258: 213-222

Dingle H (1996) Migration. The biology of life on the move. Oxford University Press, New York. 474 p

Fernandez-Jover D, Arechavala-Lopez P, Martinez-Rubio L, Tocher DR, Bayle-Sempere JT, Lopez-Jimenez JA, Martinez-Lopez FJ, Sanchez-Jerez P (2011) Monitoring the influence of marine aquaculture on wild fish communities: benefits and limitations of fatty acid profiles. Aquacult Environ Interact 2: 39-47

Fiske P, Lund RA, Hansen LP (2005) Identifying fish farm escapees. In Stock Identification Methods: Applications in Fishery Science. Ed: Cadrin SX, Friedland KD and Waldman JR. Elsevier, Amsterdam: 659-680

Fleming IA, Jonsson B, Gross MR (1994) Phenotypic divergence of sea-ranched, farmed, and wild salmon. Can J Fish Aquat Sci 51: 808-2824

Glover KA (2010) Forensic identification of farmed escapees: a review of the Norwegian experience. Aquacult Environ Interact 1:1!10

Iverson SJ (2009) Tracing aquatic food webs using fatty acids: from qualitative indicators to quantitative determination. In: Arts MT, Brett MT, Kainz M (eds) Lipids in aquatic ecosystems. Springer Science-Business Media, New York, NY, p 281-306

REFERENCES CITED

www.preventescape.eu 113

Iverson SJ, Field C, Bowen WD, Blanchard W (2004) Quantitative fatty acid signature analysis: a new method of estimating predator diets. Ecol Monogr 74: 211-235

Kerwath SE (2005) Empirical studies of fish movement behaviour and their application in spatially explicit models for marine conservation. Ph.D. Rhodes University. 227 pp

Law R (2000) Fishing, selection, and phenotypic evolution. J Mar Sci 57(3): 659-668

Loy A, Boglione C, Cataudella C (1999) Geometric morphometrics and morpho-anatomy: a combined tool in the study of seabream (Sparus aurata, Sparidae) shape. Appl Ichthyol 15: 104-110

Metcalfe J, Arnold G, McDowall R (2008) Migration. In: Fish Biology and Fisheries (Vol 1) Ed: Hart PJB and Reynolds JD., Blackwell Science, Oxford Osse JWM, van den Boogaart, JGM (1995) Fish larvae, development, allometric growth, and the aquatic environment. ICES Marine Sciences Symposium 201: 21-34

Richards RA, Esteves C (1997) Stock-specific variation in scale morphology of Atlantic coast striped bass. Trans Am Fish Soc 126: 908-918

Sanchez-Jerez P, Fernandez-Jover D, Bayle-Sempere J, Valle C, Dempster T, Tuya F, Juanes F (2008) Interactions between bluefish Pomatomus saltatrix (L.) and coastal sea-cage farms in the Mediterranean Sea. Aquaculture 282: 61-67

Sagnes P, Gaudin P, Statzner B (1997) Shifts in morphometry and their relation to hydrodynamic potential and habitat use during grayling ontogenesis. J Fish Biol 50: 846-858

Thorstad EB, Fleming IA, McGinnity P, Soto D, Wennevik V, Whoriskey F (2008) Incidence and impacts of escaped Atlantic salmon Salmo salar in nature. Report from the Technical Working Group on Escapes of the Salmon Aquaculture Dialogue. January, 2008. 113 pp

Turchini GM, Torstensen BE, Ng WK (2009) Fish oil replacement in finfish nutrition. Rev Aquacult 1: 10-57

Uglem I, Dempster T, Bjorn PA, Sanchez-Jerez P & Okland F (2009) High connectivity of salmon farms revealed by aggregation, residence and repeated movements of wild fish among farms. Mar Ecol Prog Ser 384: 251-260

Ward-Campbell BMS, Beamish WH (2005) Ontogenetic changes in morphology and diet in the snakehead, Channa limbata, a predatory fish in western Thailand. Env Biol Fish 72: 251-257