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This review summarizes the recent literature on the biology, cultivation techniques and uses of the red seaweed Palmaria palmata ((Linnaeus) Weber & Mohr 1805). The paper covers its distribution, appearance and life cycle, the state of the art cultivation techniques for spore release and seeding, and the culture of meristematic fragments of fronds harvested from natural populations. Furthermore, culture conditions for P. palmata sporelings and gametophytes and set-ups of tank and open sea culture are presented. For tank culture, relatively high irradiance and frequent seawater exchange to supply carbon dioxide and nutrients are the most important parameters. In open sea culture, site selection and system design play an important role. Land-based culture has the advantage that optimum culture conditions can be applied and quality-controlled, whereas nearshore cultivation is less costly and labour intensive. In addition, the bioremediation potential and the use of P. palmata in integrated multitrophic aquaculture (IMTA) are discussed. More research is needed to investigate bioremediation potential of different P. palmata strains. Recent developments in uses of P. palmata as food supplement, source of bioactive compounds, animal feed and compound for biofuels are presented. Finally, the possibilities of cultivation of P. palmata enhance the prospects for the expansion of the cultivation of this seaweed. However, future research is needed regarding balance of culture conditions, costs and biomass in land-based tank culture and in terms of site selection, system design, maintenance and harvest techniques in sea cultivation to establish a commercialization of the aquaculture of this species in Europe.

The bioremediation capacity of the red macroalga Palmaria palmata was assessed by two experiments. First, uptake rates of P. palmata cultured in four treatments with varying levels and ratios of the N sources ammonium (NH4 +) and nitrate (NO3 −) (18/15, 0/30, 30/45, 50/65 μM) were measured over a 3-h period to evaluate N source preference. Secondly, P. palmata were cultured in five treatments with varying levels and ratios of ammonium and nitrate (300/12, 0/312, 500/12, 0/512, 250/262 μM) for 3 weeks to evaluate specific growth rates, protein content, and ammonia toxicity. Palmaria palmata had a higher affinity for NH4 + than for NO3 − as N source. However, in the single N source trials, NO3 − uptake was higher than that of NH4 +. The maximum specific growth rate of 11.99 % day−1 was observed in the 0/512 μM ammonium/nitrate treatment after 3 weeks, whereas the minimum specific growth rate of 2.21 % day−1 was observed in the 500/12 μM ammonium/nitrate treatment after 3 weeks. NO3 − supported higher growth rates, whereas NH4 + increased tissue N, and therefore protein content. Total protein content of the algal tissue was significantly higher in P. palmata of the NH4 + treatments, reaching up to 20.6 % DW, than of those from the NO3 -treatments. Palmaria palmata showed signs of poisoning after 3 weeks in the highest NH4 + treatment. This study indicates that P. palmata is a suitable species for ecological engineering in integrated multitrophic aquaculture systems as it shows a relatively high growth performance, high nutrient uptake rates, and elevated protein content under NH4 + supply.

The concept of co-location of marine areas receives an increased significance in the light of sustainable development in the already heavily used offshore marine realm. Within this study, different spatial co-location scenarios for the coupling of offshore aquacultures and wind farms are evaluated in order to support efficient and sustainable marine spatial management strategies. A Geographic Information System (GIS) and multi-criteria evaluation (MCE) techniques were combined to index suitable co-sites in the German exclusive economic zone of the North Sea. The MCE was based on criteria such as temperature, salinity or oxygen. In total, 13 possible aquaculture candidates (seaweed, bivalves, fish and crustaceans) were selected for the scenario configuration. The GIS modelling framework proved to be powerful in defining potential co-location sites. The aquaculture candidate oarweed (Laminaria digitata) revealed the highest suitability scores at 10–20 m depth from April to June, followed by haddock (Melanogrammus aeglefinus) at 20–30 m depth and dulse (Palmaria palmata) and Sea belt (Saccharina latissima) at 0–10 m depth between April and June. In summary, results showed several wind farms were de facto suitable sites for aquaculture since they exhibited high suitability scores for Integrated Multi-Trophic Aquaculture (IMTA) systems combining fish species, bivalves and seaweeds. The present results illustrate how synergies may be realised between competing needs of both offshore wind energy and offshore IMTA in the German EEZ of the North Sea. This might offer guidance to stakeholders and assist decision-makers in determining the most suitable sites for pilot projects using IMTA techniques.

The purpose of this study was to investigate the effectiveness of 11 different culture media for production of the free-living nematode Turbatrix aceti. Several other harvesting methods were tested in addition to mass production. A further focus was the investigation of amino acid alterations caused by the application of various media during the culture of T. aceti and two additional nematode species, Panagrellus redivivus and Caenorhabditis elegans. Finally, a cost analysis for the production of T. aceti was generated and its outcome compared to the production of conventional live feed organisms. Altogether 11 liquid culture media were tested for mass production of the nematode Turbatrix aceti using a minimum of effort in terms of labour and costs. Six harvesting methods, including filtration as well as active swimming of T. aceti were evaluated. Additional to the culture of T. aceti in four of the above-mentioned media, the nematodes P. redivivus and C. elegans were cultured on two different solid media. Cost analysis for the production of T. aceti includes those of the media, the equipment, as well as the labour costs for culture and harvest. An average density of approx. 30 × 106 ± 8.13 × 106 nematodes L−1 was achieved for T. aceti. The most efficient method (20 μm filtration) allowed harvesting 85.3 ± 2.7% of the nematodes from the medium without disturbing the particles. Lowest efficiency was achieved by combining sedimentation and filtration, accomplishing a harvest of 42.1 ± 5.8%. The amino acid profile of all three nematode species turned out to be both stable and very similar. Amino acid enrichment had little effect. The costs for producing one million T. aceti individuals ranged between 5.39 and 6.19 €, where labour costs accounted for 73 to 84% of the total production costs. In conclusion, T. aceti appears to be very robust, easy to handle, as well as cheaper to cultivate compared to other live-feed organisms. Therefore, its use in commercial aquaculture should be given future consideration.

Most studies on multi-use concepts of aquaculture and wind farms explored cultivation feasibility of extractive species, such as seaweed or bivalves. However, recent studies also included the cultivation of crustaceans or fish culture in the vicinity of wind turbines. Consequently, new approaches combine fed and extractive species in integrated multi-trophic aquaculture (IMTA) concepts for offshore multi-use to reduce nutrient output and the overall environmental impact of aquaculture operations. In this chapter the findings of a series of mussel and oyster cultivation experiments over several seasons are presented, which were conducted at different offshore test sites in the German Bight. Sites were selected within future offshore wind farm areas for an explicit multi-use perspective. Results have demonstrated successful growth and fitness parameters of these candidates and therefore definitely proved the suitability of these bivalve extractive species for open ocean aquaculture. Another approach for multi-use in offshore wind farms is its use as marine protected area or even for reinforcement or restoration of endangered species, which need the absence of any fisheries activity for recovery. Current projects are testing this perspective for the native European oyster Ostrea edulis and the European lobster Homarus gammarus. From the technological point of view there are many options on how to connect aquaculture devices, such as longline and ring structures as well as different cage types, to the foundations as well as to install it in the centre of the free area between wind turbines. Next to the system design also experiments on drag forces originating from the aquaculture structure on the foundation and vice versa were investigated. Complementary to the biological, environmental end technical aspects, a number of studies were specifically targeted to address and include stakeholders, their attitudes, their interests and concerns over time. By this approach, the inclusion of stakeholders into the research process from its very beginning until today, co-production of knowledge could be fostered. Next to joint identification of the major impediments and concerns of offshore aquaculture under multi-use conditions, new issues and research questions were identified. Primary focus on the economic potential of aquaculture in offshore wind farms was shown for consumption mussels. The production of mussels using longline technology is sufficiently profitable even under the assumption of substantial cost increases. This is especially true, if existing capacities could be used. Last but not least, the EEZ is a special area-it is not a state territory even if a coastal state has its sovereign rights and jurisdiction. It is an area where three legal systems come together: International law, law of the European Union and national law. There are no mariculture projects in the German EEZ and no approval procedure has been completed so far. Some sites are not suitable for mariculture, especially because of nature conservation and shipping.

Seasonal and short-term variability of environmental parameters influence the spawning strategies of fish species. In this study, the spawning strategies and the transport of early stages of the two Cape hake species off South Africa were investigated. Distribution of eggs and larvae of Merluccius paradoxus and M. capensis was analysed in order to derive more detailed and species-specific information on spawning season, spawning location, and transport of early stages. Samples were collected during three pilot surveys between January and October 2007 and during an extensive survey in September/October 2008 in the southern Benguela upwelling system off South Africa. Eggs and larvae of M. paradoxus were found in greater numbers than those of M. capensis during all surveys. Highest abundances were found from September to October, indicating one spawning peak for M. paradoxus during late austral winter to spring. The western Agulhas Bank was identified as the primary spawning ground, and smaller spawning even...

Grote, B., Ekau, W., Stenevik, E. K., Clemmesen, C., Verheye, H. M., Lipinski, M. R., and Hagen, W. 2012. Characteristics of survivors: growth and nutritional condition of early stages of the hake species Merluccius paradoxus and M. capensis in the southern Benguela ecosystem. – ICES Journal of Marine Science, 69: 553–562. Larval mortality in marine fish is strongly linked to characteristic traits such as growth and condition, but the variability in these traits is poorly understood. We tried to identify the variability in growth in relation to conditions leading to greater survival chances for early stages of Cape hake, Merluccius paradoxus and M. capensis, in the Benguela upwelling ecosystem. During two cruises in 2007 and one cruise in 2008, hake larvae and juveniles were caught. Otolith microstructures revealed a larval age ranging from 2 to 29 days post-hatching (dph), whereas juvenile age was 67–152 dph. RNA:DNA ratios, used to evaluate nutritional condition, were above the relevant threshold level for growth. No strong coupling between growth and condition was detected, indicating a complex relationship between these factors in the southern Benguela ecosystem. Merluccius paradoxus juveniles caught in 2007 (the surviving larvae of 2006) had significantly higher larval growth rates than larvae hatched in 2007 and 2008, possibly indicating selection for fast growth in 2006. High selection pressure on growth could be linked to predation avoidance, including cannibalism.

Cape hakes, Merluccius paradoxus and M. capensis, are important gadoid fish that are commercially harvested in the Benguela Current system off Namibia and South Africa. The aim of this study was to elucidate the nutritional condition and feeding preferences of their larvae. Hake eggs and larvae were sampled in austral spring of two consecutive years, 2007 and 2008, off the west coast of South Africa. They were identified to species using genetics, and total lipid content and fatty acid (FA) composition were analysed for each individual egg and larva to compare the condition of different early life stages of both hake species. Higher abundances of M. paradoxus eggs and larvae were consistently found compared to M. capensis. In both species, eggs contained wax esters (WE) and had significantly higher lipid content per dry mass than larvae. Lipid content as well as FA composition changed with the developmental stage of larvae. Quantities of essential fatty acid (EFA) increased with feeding of larvae due to dietary lipid incorporation. In 2007, yolk-sac larvae contained significantly lower total lipids than in 2008. It is argued that this was due to reduced lipid transfer by the spawning females to the eggs. These findings indicate that maternal effects are important in determining condition of hake larvae and that this may have an effect on their survival and subsequent recruitment.

The spatial and temporal variability of the egg and larval abundance of Merluccius spp. in the Benguela Jet Current was analysed. The Cape hakes, occurring in waters off South Africa, are important for the commercial fisheries in the southern Benguela system, but information on their early life-history strategy is sparse. Data and samples, for this study, were collected during bimonthly cruises of the South African Sardine and Anchovy Recruitment Project (SARP) from August 1995 to July 2003. Samples were collected with a mini-bongo net (300 µm mesh) on a transect crossing the Benguela Current off the Cape Peninsula at 34.15°S, 18.29°E extending 58 nm offshore. Eggs and larvae were commonly found in currents with north-westerly flow, suggesting that the Benguela Jet Current transports eggs and larvae of Merluccius spp. to the northern nursery areas. Spawning grounds of Merluccius spp. appeared to be on the western Agulhas Bank during August 1996 to July 1998. Two possible spawning grounds in different water depths were identified, suggesting spawning by both Cape hake species, M. capensis and M. paradoxus. Peak abundances of eggs and larvae of Merluccius spp. were found from June to October, a time of reduced offshore transport. Abundances of eggs and larvae were low in austral summer and autumn. Spawning intensity was higher during times of reduced upwelling as shown by correlations of abundances of early life stages with the upwelling index. This leads to the assumption that the early life-history strategy of Merluccius spp. is well adapted to the variability in upwelling intensity.

By incorporating the free-swimming nematode Turbatrix aceti into early feeding regimes of the European whitefish Coregonus maraena, the suitability of this nematode species was investigated as an alternative to Artemia nauplii. During a 14-day feeding trial in a total of 25 aquaria each 1.7 L (each treatment n = 5, 255 larvae/tank) T. aceti was used either as the sole live food or in combination with Artemia nauplii or microdiet to determine the effect of T. aceti on growth performance and survival rate of C. maraena. By analysing the fatty acid composition of T. aceti prior to and after enrichment with INVE spresso® it was investigated whether the amount of n3-polyunsaturated fatty acids (n3-PUFA) in T. aceti could be further enhanced. Supplementation of Artemia nauplii with T. aceti increased growth significantly within the first 5 days of rearing in comparison to the non-supplemented food treatments (14.39 ± 0.15 mm compared to 13.44 ± 0.18 mm; mean ± SE). However, growth and survival of juvenile C. maraena on nematode-supplemented Artemia nauplii did not differ significantly from non-supplemented Artemia nauplii at the end of the 14-day rearing period (15.22 ± 0.15 mm compared to 14.86 ± 0.24 mm). All feeding treatments containing Artemia nauplii showed significantly higher growth and lower mortality at the end of the experiment in comparison to diets containing only the microdiet or T. aceti or a combination thereof. The overall low performance of T. aceti alone can most likely be explained by an insufficient capacity of C. maraena to digest this nematode species efficiently. Enrichment with INVE spresso® successfully increased the proportion of DHA in the T. aceti tissue. The results reveal that T. aceti cannot be considered a full alternative to Artemia nauplii, at least not in the rearing of C. maraena, but might be a useful vector of essential fatty acids within the early rearing period of this and potentially other fish species when provided as live food along with Artemia nauplii.

The two Cape hake species of the southern Benguela ecosystem, the shallow-waterand deep-water hakes Merluccius capensis and M. paradoxus, are economically themost important marine resources in South Africa. Recruitment is a key process inthe dynamics of marine organisms, yet very little is known about the early lifehistory of Cape hakes, especially the location of spawning grounds and transportof eggs and larvae. For each species, ichthyoplankton dispersal off South Africa issimulated by coupling oceanographic simulations to an individual-based model inorder to track virtual individuals. Results indicate that the most favorable spawningareas for transport to nursery areas are located off the south-western coast and theeastern Agulhas Bank, and highlight partly different drift routes followed by thetwo ichthyoplankton species off Cape Columbine. Transport from spawning tonursery areas is the highest in austral winter for a spawning depth rangingbetween 0 and 100 m. These modeling results are in broad agreement with avail-able knowledge on the ecology of Cape hakes. The present work on Cape hakescomplements previous modeling studies on anchovy and sardine in the same area.Taken together, these studies underline the correspondence between cross-shore(for hakes) or alongshore (for anchovy and sardine) transport mechanisms and thespawning strategies used by these key species of the southern Benguela ecosystem.KEYWORDS: Merluccius spp.; Southern Benguela; larval dispersal; modeling