Movement patterns and habitat use of the exploited swimming crab Scylla serrata (Forskal, 1775)

Mangrove ecosystems are highly productive, providing habitat for a variety of species, of which many are harvested. In times of rapid global change, due to natural as well as anthropogenic drivers, these ecosystems are increasingly placed at risk, and so are the species living within them. The mud crab Scylla serrata (Portunidae) (ForskÃÂÂ¥l, 1775) is a highly valued and exploited species associated with mangrove ecosystems in the Indo-West-Pacific. Its complex life-cycle includes a dispersing larval phase and a benthic phase as juveniles and adults. The planktonic larvae are restricted to oceanic waters, since they are stenohaline and therefore dependent on stable, high salinity conditions in order to survive. Benthic juveniles and adults are physiologically adapted to changing temperatures and varying salinities, conditions that typically occur in mangrove habitats. Movement and habitat use of large juveniles and adults are well studied and these life stages are known to move between various mangrove habitats including intertidal mangrove area flats as well as subtidal channels and flats. Females undertake long distance movements from brackish inshore waters to waters with oceanic conditions for (supposed) spawning. However, little is known about larval stages, and early benthic stages are underrepresented in the literature. The aim of this thesis is to provide deeper insights into movement patterns and habitat use at these particular life stages and to understand how these characteristics might be affected by environmental factors, such as seascape and rainfall

Effect of diet on growth, survival and fatty acid profile of marine amphipods: implications for utilisation as a feed ingredient for sustainable aquaculture

Rapidly expanding fed aquaculture demands high-quality, sustainable nutrient sources for utilisation as dietary ingredients. Exploring the potential of under-utilised resources from other industries is imperative to replace finite natural resources, such as fish meal. Marine gammarids may be an excellent source of essential fatty acids; however, their aquaculture using formulated diets remains untested in terms of survival, growth and nutritional value of the cultured product. Here, juveniles of 2 marine gammarid species, Gammarus locusta and Echinogammarus marinus, were maintained in controlled feeding experiments with 2 marine diets (Ulva spp. and Fucus spp.) and 2 terrestrial diets (lupin meal and carrot leaves). G. locusta exhibited higher survival rates, particularly when fed carrot leaves, an agricultural waste product. Fatty acid profiles of the resulting G. locusta product appear well suited for marine finfish nutrition, indicating high suitability of G. locusta as an aquaculture diet source. In contrast, whilst E. marinus may provide beneficial fatty acid profiles for aquatic animal nutrition, its poor growth performance in this study indicates that further dietary/culture research is required for this species. Our results indicate, for the first time, that marine gammarids are capable of trophic upgrading and can use non-marine diets for healthy growth in culture, but their suitability as a formulated feed ingredient for specific fish or crustacean species needs to be investigated individually. Future research should include the development of optimal large-scale production as well as investigation of optimal methods of inclusion of gammarids as feed ingredient for target aquaculture species

Amphipod meal in formulated diets for juvenile turbot Psetta maxima

Increasing fish meal prices and the depletion of natural fish stock due to fish meal production demands for novel feed ingredients in aquaculture. Marine amphipods are a natural food source for many flatfish species and are rich in essential fatty acids hence strong candidates as fish meal replacement in aquafeeds. Recent studies showed promising fatty acid profiles and fatty acid synthesis in marine amphipods, which could lower the need for fish oil supplementation in finfish feeds. In this study, juvenile turbot Psetta maxima were fed with four different diets containing different levels of amphipod meal as fish meal replacement: 0, 50 and 100 % of replacement and commercial turbot feed as reference. The experimental diets were formulated regarding basic nutritional demands without fish oil added. Growth performance as well as lipid classes and fatty acid profile in muscle and liver tissue in response to different feeding regimes were investigated

Life-history, movement, and habitat use of Scylla serrata (Decapoda, Portunidae): current knowledge and future challenges.

The mud crab Scylla serrata is a highly exploited species, associated to mangrove ecosystems in the Indo-West-Pacific. It has a complex life cycle with a dispersing larvae phase, and benthic juveniles and adults. The former are stenohaline depending on high-salinity conditions to survive, whereas the latter are physiologically well adapted to changing temperatures and salinities, conditions that typically occur in mangrove habitats. Movement and habitat use of large juveniles and adults are well studied, and these life stages are known to utilize and move between various habitats within the mangrove ecosystem: intertidal flats as well as subtidal channels and flats. Females undertake long movements from brackish inshore waters to waters with oceanic conditions for spawning.Sensory abilities—of early stages and adult stages— have hardly been studied, and little is known about larval and early benthic stages in the wild. Summarizing, the literature revealed substantial gaps in the understanding of the spatiotemporal dynamics of thedifferent life stages and of the clues that trigger recruitment, movement, and other behavior. This is the first comprehensive review on the life history, movement patterns, habitat use, and systemic role of S. serrata with emphasis on the respective life stages and geographic differences. We emphasize the need forfurther research into these processes as a basis for the sustainable management and conservation of this species

Examination of gammarid transcriptomes reveals a widespread occurrence of key metabolic genes from epibiont bdelloid rotifers in freshwater species

Previous data revealed the unexpected presence of genes encoding for long-chain polyunsaturated fatty acid (LC-PUFA) biosynthetic enzymes in transcriptomes from freshwater gammarids but not in marine species, even though closely related species were compared. This study aimed to clarify the origin and occurrence of selected LC-PUFA biosynthesis gene markers across all published gammarid transcriptomes. Through systematic searches, we confirmed the widespread occurrence of sequences from seven elongases and desaturases involved in LC-PUFA biosynthesis, in transcriptomes from freshwater gammarids but not marine species, and clarified that such occurrence is independent from the gammarid species and geographical origin. The phylogenetic analysis established that the retrieved elongase and desaturase sequences were closely related to bdelloid rotifers, confirming that multiple transcriptomes from freshwater gammarids contain contaminating rotifers’ genetic material. Using the Adineta steineri genome, we investigated the genomic location and exon–intron organization of the elongase and desaturase genes, establishing they are all genome-anchored and, importantly, identifying instances of horizontal gene transfer. Finally, we provide compelling evidence demonstrating Bdelloidea desaturases and elongases enable these organisms to perform all the reactions for de novo biosynthesis of PUFA and, from them, LC-PUFA, an advantageous trait when considering the low abundance of these essential nutrients in freshwater environments

Bewegungsmuster und Habitatsnutzung der Kommerziell genutzten Schwimmkrabbe Scylla serrata

Mangrove ecosystems are highly productive, providing habitat for a variety of species, of which many are harvested. In times of rapid global change, due to natural as well as anthropogenic drivers, these ecosystems are increasingly placed at risk, and so are the species living within them. The mud crab Scylla serrata (Portunidae) (Forskål, 1775) is a highly valued and exploited species associated with mangrove ecosystems in the Indo-West-Pacific. Its complex life-cycle includes a dispersing larval phase and a benthic phase as juveniles and adults. The planktonic larvae are restricted to oceanic waters, since they are stenohaline and therefore dependent on stable, high salinity conditions in order to survive. Benthic juveniles and adults are physiologically adapted to changing temperatures and varying salinities, conditions that typically occur in mangrove habitats. Movement and habitat use of large juveniles and adults are well studied and these life stages are known to move between various mangrove habitats including intertidal mangrove area flats as well as subtidal channels and flats. Females undertake long distance movements from brackish inshore waters to waters with oceanic conditions for (supposed) spawning. However, little is known about larval stages, and early benthic stages are underrepresented in the literature. The aim of this thesis is to provide deeper insights into movement patterns and habitat use at these particular life stages and to understand how these characteristics might be affected by environmental factors, such as seascape and rainfall

Performance and physiological responses of combined t-bar and PIT tagged giant mud crabs (Scylla serrata)

Mud crabs (Scylla spp.) are intensively caught throughout South-East Asia and support a very substantial commercial, recreational fishing and aquaculture industry. Identification of individual animals is important to improve understanding and management of this species. However, tagging of crustaceans is difficult as they frequently molt and internal tags can pose a hazard to consumers. In this pilot study we tested a new method combining passive integrated transponder tags and t-bar tags externally. 45 giant mud crabs (Scylla serrata) were captured from the wild and kept in tanks for a maximum of 10 months. We inserted tags into the abdomen of 35 giant mud crabs and tested a modified method where the combined t-bar/PIT-tag was inserted into the muscle tissue of the rear leg between the dorsal carapace plate and the top of the abdominal flap. Tagged crabs with the modified method showed 85% tag retention for molting crabs. We tested the same method in the field where 852 individuals were tagged with combined t-bar/PIT-tags of which 82 were recaptured showing 100% tag retention but without any evidence of molting having occurred. The tested method of combined t-bar/PIT-tags in giant mud crabs can further improve monitoring for wild and aquaculture populations and can be deployed widely with low cost