justification of the grow out husbandry work planned under diversify
Grow out represents the longest production phase in aquaculture and the husbandry procedures applied affect significantly the overall performance. Depending on the applied production system different methods are employed, in regards to feeding, stocking, handling, etc. Several production systems have been employed for grow out of fish including floating cages, RAS, lagoons and earthen ponds (FAO, 2003-2012). In Europe, the intensive culture of trout is successfully performed in earth ponds for several years but intensive rearing of marine species in the Mediterranean and the Atlantic is performed almost exclusively using floating cages that are anchored in protected or semi-protected areas (http://www.feap.info). Although the intensification achieved in land-based RAS systems during the 1980's allowed commercial grow out activities --especially for species such as the turbot, Scophthalmus maximus and later Senegalese sole-- the higher production costs compared to cage culture have reduced the fraction of land-based grow out systems in operation today (Mozes et al., 2011). However, in areas like the Mediterranean, for aquaculture to grow sustainably, some basic problems related to the lack of available coastal areas for farm locations due to a high site competition with other human activities should be solved. Following technological development, offshore aquaculture may provide a solution to overcome restrictions (environmental, geographical, political) regarding the present use of near shore coastal space (Ryan, 2004). To this end, the development of both appropriate technologies and use of appropriate species (large and fast growing) represent a continuous effort of the sector in recent years (EATIP, 2012). DIVERSIFY will advance already applied and develop new methodologies necessary to provide the required tools for grow out husbandry of the meagre, greater amberjack, pikeperch and mullet.
The technologies and practices used currently for meagre grow out are the same as those used for gilthead sea bream and European sea bass, although this fish presents significant differences in growth rates, feeding and spatial behaviour in the cage. Commercial diets are not available for meagre, so gilthead sea bream diets have been employed although not completely adequate. Further to the development of appropriate feeds for meagre (W8 Nutrition - meagre and WP24 Fish health - meagre) species-specific husbandry practices and methods can improve the performance during rearing. At the initial period after transfer in the cages (up to 15 g), cannibalism can be significant and increased feeding frequency is used to ameliorate the problem. As meagre grow, farmers often reduce feeding frequency to once a day, but this may not be appropriate for the species resulting in large size dispersion. Meagre presents a distinct feeding behavior and has a tendency to stay in the bottom of the cage, feed low in the water column and take time to rise towards the surface to feed. As fish are not very visible to the farmer, feeding may often not be adequate for maximum growth, resulting in large size dispersions. Meagre require approximately double the ration used for gilthead sea bream and can be fed 1–2% body weight day-1. For grow out, FCRs of 1.7 (FAO, 2005–2011b), 0.9–1.2 (Monfort, 2010) and 1.8 (Duncan et al., 2013a) have been obtained. The objectives in this WP for meagre are (i) the development of an appropriate feeding method that respects the specific behaviours of meagre and (ii) the modification of existing methodologies for cage culture related to volume and light conditions, in order to maximize the performance.
Preliminary data for grow out of greater amberjack with standard feeds, suggested that growth performance is high and wild caught individuals reached 1.8 kg body weight after 1 year (Jover et al., 1999; Mazzola et al., 2000). Hatchery produced fish reached 4 kg after 2 years and almost 7.5 after 3 years of rearing (HCMR, unpublished data), while in land-based trials fish reached 1.1 kg body weight at 1 year and increased 9 times their weight in 4 years (Jerez et al., 2007). Studies on the effects of feeding frequency, feed rations, and food type during grow out have been carried out in tanks, so far, in order to improve growth and health of fish (Jerez et al., 2009a,b; 2011), but further studies, performed in the frame DIVERSIFY, are required to define proper feeding strategies. As the applied methodologies for grow out are adaptations from other species (as for meagre) that have a final size of only 20% of the greater amberjack, it is essential that DIVERSIFY will develop appropriate techniques for cage rearing with the main objectives being (i) to identify the adequate volume for the rearing, based on the experience from other Seriola spp (FAO, 2012) and (ii) to test the application of submersible cages as this technology is targeted for offshore locations and can also serve as a method to prevent parasitic infestations during rearing. Finally, DIVERSIFY will address the development of appropriate management practices related to the specific thermal ranges for optimal growth and health, for appropriate site selection for cage culture and the optimum rearing density, a parameter that affects the performance of the reared populations.
One of the bottlenecks identified by pikeperch SMEs is the unpredictable depression of growth observed sometimes during fish grow out. This increases production costs, while management manipulations are often followed by high mortalities with unknown causes. Reduced growth and/or high mortality can be related to high stress responsiveness to intensive culture conditions and to the use of pikeperch broodstock of various domestication levels, including wild populations (Teletchea & Fontaine, 2012). Depending on the stressor and species sensitivity, allostatic load may turn into allostatic overload and stress response may shift from adaptive to maladaptive, resulting in a continued loss of homeostasis (Shreck et al., 2001; Barton, 2002; Pruett, 2003; Segner et al., 2011). Moreover, due to the associated allostatic costs, less energy would be available for other energy-demanding biological functions, such as growth and resistance to disease. In the Eurasian perch (Perca fluviatilis) a stress-induced growth reduction (by 35%) has been reported (Jentoft et al., 2005). Although it is suggested that stress can impact negatively the fish immune system, this cannot be generalized and currently no information exists on stress sensitivity and subsequent immune effects in pikeperch, necessitating further investigation. Also, reduction of stress responsiveness may be an important part of domestication, because of the positive selection of stress-resistant animals (thus displaying improved fitness) along generations (Douxfils et al., 2011, 2012) and studying the influence of domestication level and geographical origin is important. Likewise, the levels of stress indicators following exposure to chronic stressors have been shown to be heritable in salmonids and European sea bass (Pottinger & Carrick, 1999a, b). Geographic origin may also influence significantly the growth potential of percid fish (Mandiki et al., 2004), and their physiological response to environmental conditions. The DIVERSIFY objectives for grow out of pikeperch are to study the effect of (i) husbandry practices and environmental factors on growth, immune and physiological status and (ii) of domestication level and geographical origin on growth and stress sensitivity and immune performances.
Presently, most grey mullet are reared extensively in polyculture systems (Whitfield et al. 2012) and to a lesser degree as a bio-remedial approach to improve the anoxic environment under marine fish cages (Katz et al., 2002; Lupatsch et al., 2003). However, in order for EU countries to supply an established market in North Africa and the growing demand in the Mediterranean, the intensive monoculture of grey mullet has to be developed. One of the major obstacles to achieve this is the lack of a suitable and economical grow-out feed. This issue will be addressed in the Nutrition GWP, which will focus on improving a non-fishmeal grow-out grey mullet diet through determining taurine and essential fatty acid requirements. Recently, the IOLR in Eilat has grown in monoculture F1 grey mullet in 40 m3 tanks in an open seawater (40 psu) system. The females reached 1.9 kg in 30 months and were fed a commercial fish-protein based diet for bass. In addition, over 85% of these females demonstrated ripe ovaries during the spawning season. Importantly, the fact that F1 fish were used implies that grey mullet grown in captivity may perform better under grow-out conditions than wild caught juveniles. On the other hand, the grow-out period from this study was too long for commercial consideration and the FCR was very high (approximately 3.0) while the stocking density and nitrogen retention of fish in these ponds were low (about 15 kg m-3 and 15%, respectively). Moreover, maximum growth, feed conversion efficiency and intestinal enzyme activity has been shown to take place at 10 psu (Barman et al., 2005). Bakeer (2006) found that increasing stocking densities from 1-3 fish m-2 in 12 psu saline water ponds increased fish yield from 213 kg per 1000 m2 to 459 kg per 1000 m2, respectively, after 8 months. Nevertheless, there was no benefit to overall profitability with increasing density as growth rate was insufficient to offset the rising operating costs of fingerling and food purchase. The Israeli SME DOR, using a commercial carp feed and stocking 0.5 and 1 fish m-2 in 6000 m2 ponds showed yields of about 500 and 1000 kg per 1000 m2, respectively after about 1 year. Taken together, these results suggest the importance of an effective feed in grey mullet culture in order to improve higher density performance. To this end, the aims of the grey mullet studies in this GWP are to (1) test and compare the performance of an improved grow out feed, in terms of FCR, PER, SGR and survival, on F1 and wild caught fish at two stocking densities (0.5 and 1 juvenile/m2) and (2) compare the performance of this feed under the different environmental conditions of commercial farms in Israel, Greece and Spain, which span the Mediterranean Sea.
The technologies and practices used currently for meagre grow out are the same as those used for gilthead sea bream and European sea bass, although this fish presents significant differences in growth rates, feeding and spatial behaviour in the cage. Commercial diets are not available for meagre, so gilthead sea bream diets have been employed although not completely adequate. Further to the development of appropriate feeds for meagre (W8 Nutrition - meagre and WP24 Fish health - meagre) species-specific husbandry practices and methods can improve the performance during rearing. At the initial period after transfer in the cages (up to 15 g), cannibalism can be significant and increased feeding frequency is used to ameliorate the problem. As meagre grow, farmers often reduce feeding frequency to once a day, but this may not be appropriate for the species resulting in large size dispersion. Meagre presents a distinct feeding behavior and has a tendency to stay in the bottom of the cage, feed low in the water column and take time to rise towards the surface to feed. As fish are not very visible to the farmer, feeding may often not be adequate for maximum growth, resulting in large size dispersions. Meagre require approximately double the ration used for gilthead sea bream and can be fed 1–2% body weight day-1. For grow out, FCRs of 1.7 (FAO, 2005–2011b), 0.9–1.2 (Monfort, 2010) and 1.8 (Duncan et al., 2013a) have been obtained. The objectives in this WP for meagre are (i) the development of an appropriate feeding method that respects the specific behaviours of meagre and (ii) the modification of existing methodologies for cage culture related to volume and light conditions, in order to maximize the performance.
Preliminary data for grow out of greater amberjack with standard feeds, suggested that growth performance is high and wild caught individuals reached 1.8 kg body weight after 1 year (Jover et al., 1999; Mazzola et al., 2000). Hatchery produced fish reached 4 kg after 2 years and almost 7.5 after 3 years of rearing (HCMR, unpublished data), while in land-based trials fish reached 1.1 kg body weight at 1 year and increased 9 times their weight in 4 years (Jerez et al., 2007). Studies on the effects of feeding frequency, feed rations, and food type during grow out have been carried out in tanks, so far, in order to improve growth and health of fish (Jerez et al., 2009a,b; 2011), but further studies, performed in the frame DIVERSIFY, are required to define proper feeding strategies. As the applied methodologies for grow out are adaptations from other species (as for meagre) that have a final size of only 20% of the greater amberjack, it is essential that DIVERSIFY will develop appropriate techniques for cage rearing with the main objectives being (i) to identify the adequate volume for the rearing, based on the experience from other Seriola spp (FAO, 2012) and (ii) to test the application of submersible cages as this technology is targeted for offshore locations and can also serve as a method to prevent parasitic infestations during rearing. Finally, DIVERSIFY will address the development of appropriate management practices related to the specific thermal ranges for optimal growth and health, for appropriate site selection for cage culture and the optimum rearing density, a parameter that affects the performance of the reared populations.
One of the bottlenecks identified by pikeperch SMEs is the unpredictable depression of growth observed sometimes during fish grow out. This increases production costs, while management manipulations are often followed by high mortalities with unknown causes. Reduced growth and/or high mortality can be related to high stress responsiveness to intensive culture conditions and to the use of pikeperch broodstock of various domestication levels, including wild populations (Teletchea & Fontaine, 2012). Depending on the stressor and species sensitivity, allostatic load may turn into allostatic overload and stress response may shift from adaptive to maladaptive, resulting in a continued loss of homeostasis (Shreck et al., 2001; Barton, 2002; Pruett, 2003; Segner et al., 2011). Moreover, due to the associated allostatic costs, less energy would be available for other energy-demanding biological functions, such as growth and resistance to disease. In the Eurasian perch (Perca fluviatilis) a stress-induced growth reduction (by 35%) has been reported (Jentoft et al., 2005). Although it is suggested that stress can impact negatively the fish immune system, this cannot be generalized and currently no information exists on stress sensitivity and subsequent immune effects in pikeperch, necessitating further investigation. Also, reduction of stress responsiveness may be an important part of domestication, because of the positive selection of stress-resistant animals (thus displaying improved fitness) along generations (Douxfils et al., 2011, 2012) and studying the influence of domestication level and geographical origin is important. Likewise, the levels of stress indicators following exposure to chronic stressors have been shown to be heritable in salmonids and European sea bass (Pottinger & Carrick, 1999a, b). Geographic origin may also influence significantly the growth potential of percid fish (Mandiki et al., 2004), and their physiological response to environmental conditions. The DIVERSIFY objectives for grow out of pikeperch are to study the effect of (i) husbandry practices and environmental factors on growth, immune and physiological status and (ii) of domestication level and geographical origin on growth and stress sensitivity and immune performances.
Presently, most grey mullet are reared extensively in polyculture systems (Whitfield et al. 2012) and to a lesser degree as a bio-remedial approach to improve the anoxic environment under marine fish cages (Katz et al., 2002; Lupatsch et al., 2003). However, in order for EU countries to supply an established market in North Africa and the growing demand in the Mediterranean, the intensive monoculture of grey mullet has to be developed. One of the major obstacles to achieve this is the lack of a suitable and economical grow-out feed. This issue will be addressed in the Nutrition GWP, which will focus on improving a non-fishmeal grow-out grey mullet diet through determining taurine and essential fatty acid requirements. Recently, the IOLR in Eilat has grown in monoculture F1 grey mullet in 40 m3 tanks in an open seawater (40 psu) system. The females reached 1.9 kg in 30 months and were fed a commercial fish-protein based diet for bass. In addition, over 85% of these females demonstrated ripe ovaries during the spawning season. Importantly, the fact that F1 fish were used implies that grey mullet grown in captivity may perform better under grow-out conditions than wild caught juveniles. On the other hand, the grow-out period from this study was too long for commercial consideration and the FCR was very high (approximately 3.0) while the stocking density and nitrogen retention of fish in these ponds were low (about 15 kg m-3 and 15%, respectively). Moreover, maximum growth, feed conversion efficiency and intestinal enzyme activity has been shown to take place at 10 psu (Barman et al., 2005). Bakeer (2006) found that increasing stocking densities from 1-3 fish m-2 in 12 psu saline water ponds increased fish yield from 213 kg per 1000 m2 to 459 kg per 1000 m2, respectively, after 8 months. Nevertheless, there was no benefit to overall profitability with increasing density as growth rate was insufficient to offset the rising operating costs of fingerling and food purchase. The Israeli SME DOR, using a commercial carp feed and stocking 0.5 and 1 fish m-2 in 6000 m2 ponds showed yields of about 500 and 1000 kg per 1000 m2, respectively after about 1 year. Taken together, these results suggest the importance of an effective feed in grey mullet culture in order to improve higher density performance. To this end, the aims of the grey mullet studies in this GWP are to (1) test and compare the performance of an improved grow out feed, in terms of FCR, PER, SGR and survival, on F1 and wild caught fish at two stocking densities (0.5 and 1 juvenile/m2) and (2) compare the performance of this feed under the different environmental conditions of commercial farms in Israel, Greece and Spain, which span the Mediterranean Sea.
