Temperate Water Species Research Articles

Decadal changes in value of dried sea cucumbers (bêche-de-mer) in Hong Kong markets

Sea cucumbers in their dried form, bêche-de-mer or trepang, have been in high demand for four decades, causing relentless exploitation pressure on fisheries. Key aspects unknown are the temporal trends in prices of different species and potential impacts of external factors. We recorded prices and measured dried specimens of 20 sea cucumber species in 38 retail shops in Hong Kong in 2022 and compared prices obtained for 15 of these species in the same market in 2011 and/or 2016. Two temperate-water species (Apostichopus japonicus and A. nigripunctatus) were the most valuable but declined slightly in price over the 11-year period. All of the tropical species rose in price. Holothuria lessoni emerged as the most valuable tropical species (average: USD$503) and was scarce in the marketplace. Two Indo-Pacific species recently enlisted on CITES Appendix II, H. nobilis and H. whitmaei, were also seldom found in the marketplace and their value had risen greater than inflationary expectations. Also rare in the marketplace was the high-valued Isostichopus badionotus. Larger specimens of A. japonicus and H. scabra demanded exponentially higher prices than small individuals, with implications for fisheries and aquaculture. Significant aquaculture production for both of these species does not appear to have greatly quelled market demand. Despite potential disruptions during the COVID pandemic, overall demand for bêche-de-mer remains strong. The increases in retail prices for certain over-exploited species, potentially exacerbated by trade restrictions from CITES listings, beckons careful resource monitoring by fishery managers and continuing opportunities for aquaculture programs.

Ocean warming and novel species interactions boost growth and persistence of range‐extending tropical fishes but challenge that of sympatric temperate species in temperate waters

AbstractAimClimate change can have a broad range of impacts on the physiology and behaviour of animals. These effects can be mediated by the presence of other species in the community, but current forecasts of species responses to climate change largely ignore biological interactions. This is particularly true for novel interactions between range‐extending and native species, as this is often considered as noise and excluded from predictive models. Here we simulate how a tropical range‐extending and a local temperate fish species respond to the independent and combined effects of future ocean warming (RCPs 4.5 and 8.5) and novel ecological interactions in temperate ecosystems.LocationEast coast of Australia, along a ~ 2,000 km latitudinal gradient in a global climate warming hotspot.TaxonAbudefduf vaigiensis (tropical) and Atypicthys strigatus (temperate) fishes.MethodsWe use a dynamic energy budget model to simulate the length growth (i.e., increases in body length of individuals over time) and population persistence of juveniles of a tropical and a temperate fish species that form mixed‐species shoals, under different climate scenarios with and without the effects of novel ecological interactions.ResultsOur model forecasts that length growth of the juvenile tropical species will increase under ocean warming across subtropical to temperate regions. This increased length growth will be more drastic in temperate regions than in the subtropics, as winter warming will allow the tropical species to overwinter more frequently and show positive growth throughout the year. In contrast, warmer summer temperatures in the subtropics will likely exceed the optimal temperature of the juvenile temperate species at their trailing edge, resulting in reduced length growth under climate warming. Novel species interactions increased length growth of the juvenile tropical species but did not affect its winter or summer survival. In contrast, novel species interactions with tropical species were forecast to reduce length growth of the juvenile temperate species.Main ConclusionsOur study suggests that for some coastal fish species future warming will likely reverse body size dominance between temperate and tropical fish species, with increased novel interactions in temperate ecosystems (due to range extensions) but decreased novel interactions in the subtropics (due to range contractions). Novel species interactions and warming effects on body size and species survival are likely to reshuffle temperate fish communities and their competitive interactions.

Clogging nets-Didemnum vexillum (Tunicata: Ascidiacea) is in action in the eastern Mediterranean

Abstract Didemnum vexillum is an aggressive, rapidly growing colonial ascidian and regarded as a global alien invasive species in temperate waters. It has recently become established in the western Mediterranean and the vectors of its introduction were assumed to be shipping or oyster trade. A dense settlement of it was encountered on nets of the bluefin tuna (Thunnus thynnus) cages placed at 60–65 m depths off the İzmir Peninsula (eastern Aegean Sea, eastern Mediterranean) in December 2022. It had considerably clogged net's eye openings, hindering water circulations inside cages. It had a vertical distributional pattern on 35 m long-nets, occurring solely on depths from surface down to 15 m, around where a summer thermocline develops. It has entirely replaced the native black mussel Mytilus galloprovincialis on nets. This colonial ascidian changed the routine cleaning procedure of nets in the farming. Three possible ways of its introduction to the eastern Mediterranean were proposed, but the most reasonable one is its secondary transfer via nets or ships from Malta. Mechanisms of its invasion biology and behaviour should be studied and monitored in the region.

Ichthyoplankton of The Shelf and Deep Water Areas of the North and Northeast of the Black Sea in The Spring Season

This paper is focused on the ichthyoplankton species composition and spatial distribution in the Black sea shelf zone and the deepwater regions off Crimean Peninsula and coast of the Caucasus during the spring hydrological season. Recent changes in the hydrological regime of the Black sea induced by the climate warming have led to an extension of the active and productive spawning of the dominant temperate-water species Sprattus sprattus until the end of the spring hydrological season. An intensive spawning of sprat was detected in March, April and May 2016, 2017 and 2019, which was confirmed by a predominance of younger age group larvae. The maximum number of eggs reached 224 ind./m2 , and the larvae - 116 ind./m2. The wide size range of larvae as well as the low proportion of larvae with empty guts evidenced a favorable fodder base for their survival. The reduction in the age and sizeweight composition of sprat stock in the Black sea observed since 2016 as a result of an increase in its commercial fishing on the shelf of the Crimean Peninsula, did not affect sprat’ spawning activity.

Northward Migration of Antarctic Polar Front during the Quaternary: Planktic Foraminiferal Record from Southeast Indian Ocean

The ODP Hole 763A is influenced by the northward-flowing cold West Australian Current (WAC) and Southward flowing warm Leeuwin Current (LC). LC is a branch of the South Equatorial Current (SEC), which brings relatively warmer waters from the tropical Pacific Ocean into the Indian Ocean via Indonesian Throughflow (ITF). The modern planktic foraminiferal fauna thrives along the western margin of Australia. It consists mainly of warm water assemblages brought by the LC. The present study provides planktic foraminiferal census data from ODP Hole 763A, influenced by the LC and WAC, to document the history of cold water influence at the site during the quaternary. The northward migration of the Antarctic Polar Front (APF) and resultant intensification of the cold West Australian Current have been inferred based on the dramatic increase in the relative abundance of temperate water species group Globoconella at Hole 763A situated in the low latitude region. The Quaternary planktic foraminiferal census data shows several episodes of invasion of Globoconella. These intervals of high abundance of Globoconella group have been attributed to the intensification of WAC, probably due to Antarctic ice volume expansion and resultant northward migration of the APF at 0.05 Ma, 0.2 Ma, 0.45 Ma, 0.7 Ma and 1.2 Ma. We have documented that the amplitude of fluctuations in cold/warm events has increased after the Mid-Pleistocene Transition (MPT). LC is a heat supplier to the higher latitudes, its weakening during such intervals might have contributed to the ice volume expansion over Antarctica. Thus, the study proposes that the Antarctic ice cap formation creates a positive feedback mechanism by lowering sea level, reduced strength of LC due to a decrease in ITF and less heat supply towards the South Pole. All these phenomena add to further cooling.

Response of a natural Antarctic phytoplankton assemblage to changes in temperature and salinity

The climate around the Western Antarctic Peninsula (WAP) is rapidly changing and dramatically affecting marine coastal waters. Increases in air and seawater temperatures, not matter how small, can alter coastal biological communities due to both temperature increases as well as salinity reduction from glacier melting. The aim of this study was to evaluate the individual and combined effects of elevated sea surface temperature (+4 °C) and decreased salinity (−4) on growth and assemblage composition of natural summer phytoplankton from Potter Cove (King George Island, South Shetlands, northern WAP), using an outdoor microcosm experiment. Pigment composition was analyzed by high performance liquid chromatography (HPLC/Chemtax) and species composition by light and electron microscopy. Increases in phytoplankton biomass during the first 3 days at elevated-temperatures coincided with an increase in the abundance and the specific growth rate of small centric diatoms (Chaetoceros socialis and Shionodiscus gaarderae, mostly observed in temperate waters) and unidentified small phytoflagellates <5 μm. In contrast, pennate diatoms significantly decreased. At the end of the experiment on day 7, under nitrate and phosphate limitation, chlorophytes abundances increased under low salinity whereas prasinophytes decreased in all treatments. This study suggests that climate change could notably affect Antarctic phytoplankton composition by favouring temperate-water species previously undetected in Antarctic waters, such us S. gaarderae. Moreover, the observed changes in phytoplankton structure, associated with an increase of nano- over micro-size taxa, could have important implications for future Antarctic food webs.

Reproductive biology of the ascidians Styela rustica and Halocynthia pyriformis from Kongsfjorden, Svalbard, Arctic

Ascidians are abundant and well-represented members of worldwide benthic communities, including Antarctica and the Arctic. These organisms exhibit different reproductive patterns usually related to a latitudinal gradient, as do many marine invertebrate species. Reproductive seasonality varies from one or two annual peaks in cold and temperate water species to continuous reproduction throughout the year in warm water species. Styela rustica (Linnaeus 1767) and Halocynthia pyriformis (Rathke 1806) are solitary species with external fertilization and a wide distribution range, from the North Atlantic to the Arctic. The reproductive patterns of these two species were assessed for Arctic populations by year-round sampling and structural analysis of the gonads. Both species are hermaphrodites and showed marked seasonality in oocyte maturity and spawning; S. rustica peaked during the boreal summer and H. pyriformis in late spring. The two species also showed marked differences in mature oocyte sizes: H. pyriformis almost doubled those of S. rustica and, while spermatocytes of H. pyriformis were mature year-round, the maturity of male and female gametes was synchronized in S. rustica. The species thus showed an annual reproductive cycle coupled with a higher production period in the ecosystem, but also exhibited different strategies developed under the same environmental pressures.

Seasonal distribution of the Black Sea ichthyoplankton near the Crimean Peninsula

Pattern of species composition and spatial distribution of the Black Sea ichthyoplankton in open waters near the Crimean Peninsula in different seasons of the year are based on the studies of materials collected during eight expeditions of the Research Vessel (R/V) ”Professor Vodyanitsky” from 2011 to 2016. We noted an increase in abundance and species diversity of ichthyoplankton during the spawning season, indicating positive changes in the plankton community of the Black Sea. Favourable temperature conditions for embryonic and postembryonic development as well as rich nutrient items contributed to the spawning season prolongation of the mass fish species of the Black Sea in recent years. In previous years, larvae of the thermophilic species Engraulis encrasicolus, dominating in summer ichthyoplankton species, were collected from June to September, but in recent years, they have begun to appear from May to October. Intensive spawning of the temperate-water species Sprattus sprattus dominating in the winter ichthyoplankton, has been observed in November, at the end of the autumn hydrological season, while its larvae are detected all year round. Prolongation of the productive spawning of thermophilic and temperate-water fish species results in the simultaneous appearance of their larvae in the sea. An increased population of short-cycle species facilitates the appearance of new species of temperate-water Mediterranean predators, namely Trisopterus luscus and Molva macrophthalma. Their eggs and larvae are detected in the ichthyoplankton, indicating favourable conditions for their spawning and the survival of the early larval stages

A long way from home: Biosecurity lessons learnt from the impact of La Niña on the transportation and establishment of tropical portunid species.

Marine ecosystems can be modified and shaped by irregular interannual variations in oceanic current patterns and temperatures, such as El Niño and La Niña. These large scale oceanic events have also been shown to influence environmental stressors such as invasive marine species (IMS). Our study indicates that there is a causative link between these climatic events, and atypical detections of native and IMS. Significant La Niña events between 1970 and 2014 were associated with sightings of tropical crab species in temperate waters following a lag period of 18–24 months from the onset of the event. We identified a total of 72 records of six tropical portunid crabs species (from both Charybdis and Scylla) in temperate waters of south-western Australia following these La Niña events, based on reports in published scientific literature, grey literature and museum records, as well as citizen science networks such as FishWatch and PestWatch apps. We suggest that La Niña conditions facilitated transportation and temporary establishment of crab larvae from their native tropical habitat to temperate regions. As the strength of La Niña events is likely to increase into the future due to the escalating effects of climate change, it is likely that there will be a growth in associated atypical establishment events of IMS. Consequently, biosecurity managers will need to reprioritise resources in order to accommodate the potential impacts of these large scale oceanic events as part of their surveillance programmes.

Molecular Structures and Coding Genes of the Water-Borne Protein Pheromones of Euplotes petzi, an Early Diverging Polar Species of Euplotes.

Euplotes is diversified into dozens of widely distributed species that produce structurally homologous families of water-borne protein pheromones governing self-/nonself-recognition phenomena. Structures of pheromones and pheromone coding genes have so far been studied from species lying in different positions of the Euplotes phylogenetic tree. We have now cloned the coding genes and determined the NMR molecular structure of four pheromones isolated from Euplotes petzi, a polar species which is phylogenetically distant from previously studied species and forms the deepest branching clade in the tree. The E.petzi pheromone genes have significantly shorter sequences than in other congeners, lack introns, and encode products of only 32 amino acids. Likewise, the three-dimensional structure of the E.petzi pheromones is markedly simpler than the three-helix up-down-up architecture previously determined in another polar species, Euplotes nobilii, and in a temperate-water species, Euplotes raikovi. Although sharing the same up-down-up architecture, it includes only two shortα-helices that find their topological counterparts with the second and third helices of the E.raikovi and E.nobilii pheromones. The overall picture that emerges is that the evolution of Euplotes pheromones involves progressive increases in the gene sequence length and in the complexity of the three-dimensional molecular structure.

Response of a temperate demersal fish community to global warming

Changes in the distribution of the demersal fish species have been identified in north-European Atlantic waters. The consequence of these changes has been a northward shift of the distribution limits and changes in richness. In this study a notable increase in demersal fish species richness per sampling station was detected in the southern Bay of Biscay. This rise was due to an increase in frequency of occurrence and abundance of the majority of fish species in the area (53% from the total species). A fisheries relate explanation was discarded because the mismatch between the changes in the fishing effort and the augment in frequency of occurrence and abundance. On the contrary, these changes are in agreement with expected response under the increasing temperature of the sea observed over the last three decades, associated to global warming. These changes were positively correlated with an increase in temperature of intermediate waters in the study area. In addition, some of these species showed a notable western displacements of the Centre of Gravity in the study area, which would be expected if temperate water species would be favoured by an increase in water temperature. Our results are consistent with studies in the North Sea, where many of these species showing widened distribution limits towards north. The analysis of the results shows that the studied ecosystem, the Bay of Biscay is under a meridionalization process. On the other hand, only one tropicalization event (Lepidotrigla dieuzeidei), was recorded, maybe due to the conservative restrictions applied in species selection.

Pliocene and Pleistocene paleoceanography in the western subarctic Pacific based on diatom analyses of ODP Leg 145 Hole 884B and IODP Expedition 323 Holes U1341B and U1343E

Late Pliocene–Pleistocene fossil diatom assemblages from Ocean Drilling Program (ODP) Leg 145 Hole 884B in the western subarctic Pacific were investigated to improve the diatom biostratigraphy. Moreover, the paleoceanographic records at Hole 884B were compared with those in Integrated Ocean Drilling Program (IODP) Expedition 323 Holes U1341B and U1343E in the Bering Sea for the time interval of 2.5–0Ma in order to clarify the differences in the diatom assemblage fluctuations and the history of past ocean circulations around the subarctic Pacific. In Hole 884B, five diatom zones from the Neodenticula koizumii–Neodenticula kamtschatica Zone to the Neodenticula seminae Zone were identified. The decreases in the relative abundance of temperate-water species were recognized at ca. 1.9Ma in Hole U1343E, ca. 2.1Ma in Holes 884B and U1341B. The decreases of the temperate-water species at these sites indicate that a widespread cooling event must have occurred over the subarctic Pacific at ~2Ma. In addition, the continuous low occurrences of the sea-ice related species from around 2Ma onward, which indicate the presence of sea-ice, were observed at Sites 884 and U1341. We also point out that the age differences in decrease of temperate-water species at the three sites (i.e., delay in response of the temperate-water species at Site U1343) may be related to changes of seawater inflow from the North Pacific to Sites U1341 and U1343 and of the East Kamchatka Current from the Bering Sea to Site 884.

Histology and histochemistry of the reproductive potential of Acartia clausi (copepoda: calanoida)

The seasonal fluctuations in zooplankton densities in temperate climates have been long known and the multiplicity of performed studies identified a vast number of factors responsible for these phenomena, such as changes in the physico-chemical factors and other such types of environmental forces governing them. Acartia clausi is a euryaline temperate-boreal species very common in the Portuguese coastal ecosystems, in both estuarine and coastal waters. It is usually described as a temperate water species of neritic calanoid copepod, which is associated with warmer water regions, and as a result becomes more abundant in the summer months, reaching a biomass maximum during the months of July and August. Growth and egg production have been studied extensively in some Acartia species. In the present study histology and histochemistry were selected to determine the reproductive potential of A. clausi.The ovigerous females were identified with a binocular microscope, isolated and fixed in the Bouin’s solution for histological (5 om thickness, mounting and Haematoxylin - Eosin staining) and histochemical analysis (Periodic Acid Schiff method (PAS) with Haematoxylin as a counter stain for the identification of the carbohydrate content and vitellogenic oocytes. The size of the oocytes was evaluated through measurements made with a micrometer.The microscopic studies and Image analysis indicated that, in the month of September, the majority of the oocytes were immature and had reduced or almost negligible carbohydrate contents with very few vitellogenic oocytes (Figure 1 A and B), while the specimens from the month of March exhibited a large difference in the oocyte dimensions. These were mature and more vitellogenic and occupied almost half the volume of the body (Figure 1 C, D and E). This shows that, during the month of September, the environmental conditions are not favorable for the maturation of gonads in these species while in the month of March they proliferate and the species shows a high degree of reproductive potential.This work forms a valid approach in understanding the population fluctuations and reproductive status in a key species of copepod showing a particular temporal variation associated with its reproductive strategy.

Marine turtle threats in Uruguayan waters: insights from 12 years of stranding data

We present the first study conducted in a wide spatio-temporal scale on marine turtles strandings (N = 1,107) over a 12-year period (1999–2010) in Uruguay. Five species were recorded Chelonia mydas (N = 643; 58.1 %), Caretta caretta (N = 329; 29.7 %), Dermochelys coriacea (N = 131; 11.8 %), Eretmochelys imbricata (N = 3; 0.3 %), and Lepidochelys olivacea (N = 1; 0.1 %). The first three species stranded throughout the Uruguayan coast, but differences in distribution patterns were detected among species. Although occurring year round, stranding records show a clear seasonal pattern with variation in monthly distribution among species, but with a peak of records in austral summer. Strandings provide indirect evidence of threats to marine turtles in Uruguayan and surrounding waters, particularly fisheries and marine debris. Our results demonstrate that Uruguayan coastal waters likely serve as a foraging or development area for at least three endangered marine turtle species in temperate waters.

A 600-ka Arctic sea-ice record from Mendeleev Ridge based on ostracodes

Arctic paleoceanography and sea-ice history were reconstructed from epipelagic and benthic ostracodes from a sediment core (HLY0503-06JPC, 800 m water depth) located on the Mendeleev Ridge, Western Arctic Ocean. The calcareous microfaunal record (ostracodes and foraminifers) covers several glacial/interglacial cycles back to estimated Marine Isotope Stage 13 (MIS 13, ∼500 ka) with an average sedimentation rate of ∼0.5 cm/ka for most of the stratigraphy (MIS 5–13). Results based on ostracode assemblages and an unusual planktic foraminiferal assemblage in MIS 11 dominated by a temperate-water species Turborotalita egelida show that extreme interglacial warmth, high surface ocean productivity, and possibly open ocean convection characterized MIS 11 and MIS 13 (∼400 and 500 ka, respectively). A major shift in western Arctic Ocean environments toward perennial sea ice occurred after MIS 11 based on the distribution of an ice-dwelling ostracode Acetabulastoma arcticum. Spectral analyses of the ostracode assemblages indicate sea ice and mid-depth ocean circulation in western Arctic Ocean varied primarily at precessional (∼22 ka) and obliquity (∼40 ka) frequencies.

Do marine substrates ‘look’ and ‘sound’ the same? Supervised classification of multibeam acoustic data using autonomous underwater vehicle images

In this study we outline the techniques used to transform multibeam acoustic data into spatial layers that can be used for predictive habitat modelling. The results allow us to identify multibeam attributes which may act as potential surrogates for environmental variables that influence biodiversity and define which variables may be reliable for predicting the distribution of species in temperate waters. We explore a method for analysing the spatially coincident multibeam bathymetric and backscatter data from shallow coastal waters to generate spatial data products that relate to the classes derived from fine-scale visual imagery obtained using an autonomous underwater vehicle (AUV). Classifications of the multibeam data are performed for substrate, rugosity and sponge cover. Overall classification accuracies for the classes associated with substratum, rugosity and sponge structure were acceptable for biodiversity assessment applications. Accuracies were highest for rugosity classes at 65%, followed by substratum classes at 64% and then sponge structure classes at 57%. Random forest classifiers at a segmentation scale of 30 performed best in classifying substratum and rugosity, while K-nearest neighbour classifiers performed best for sponge structure classes, with no difference in accuracy between scale 30 and 60. Incorporating backscatter variables using segmentation improved the overall accuracy achieved by the best performing model by between 1% (rugosity) and 9% (substratum) above using topographic variables only in the grid-based analyses. Results suggest that image-based backscatter classification show considerable promise for the interpretation of multibeam sonar data for the production of substrate maps. A particular outcome of this research is to provide appropriate and sufficiently fine-scale physical covariates from the multibeam acoustic data to adequately inform models predicting the distribution of biodiversity on benthic reef habitats.

Detection of the tropical mussel species Perna viridis in temperate Western Australia: possible association between spawning and a marine heat pulse

In April 2011 a single individual of the invasive mussel Perna viridis was detected on a naval vessel while berthed in the temperate waters of Garden Island, Western Australia (WA). Further examination of this and a nearby vessel revealed a small founder population that had recently established inside one of the vessel’s sea chests. Growth estimates indicated that average size mussels in the sea chest were between 37.1 and 71 days old. Back calculating an ‘establishment date’ from these ages placed an average sized animal’s origins in the summer months of January 2011 to March 2011. This time period corresponded with an unusual heat pulse that occurred along the WA coastline resulting in coastal waters >3 oC above normal. This evidence of a spawning event for a tropical species in temperate waters highlights the need to prepare for more incursions of this kind given predictions of climate change.

Estimating optimal salinity and temperature of chaetognaths

Determining optimal temperature and salinity for marine organisms is a challenge for marine ecologists because not every species can be easily maintained in the laboratory for testing the influence of environmental parameters. To find a simple method to estimate the optimal temperature and salinity for marine organisms based on survey data, a reciprocal quadratic yield-density model was used for determining the optimal temperature or salinity from abundance data for six pelagic Chaetognatha species. The data for the modelling were collected in four surveys in the East China Sea (23°30′–33°N 118°30′–128°E) from 1997 to 2000. According to both survey data and results from the models, we analysed qualitatively and quantitatively the ecological characteristics of those species. Estimated optimal temperatures and salinities are 17.3°C and 14.1‰ for Sagitta nagae, 20.3°C and 13.8‰ for S. bedoti, 24.9°C and 32.9‰ for S. enflata, 22.5°C and 16.5‰ for S. ferox, 24.5°C and 34.1‰ for S. pacifica and 17.3°C and 14.1‰ for S. pulchra, respectively. Three ecological groups were evident in the East China Sea: the neritic, warm temperate water species (S. nagae); the neritic, warm water species (S. pulchra, S. ferox and S. bedoti); and the oceanic, warm water species (S. enflata and S. pacifica). Our results validate that the model is applicable for describing the relationship between chaetognaths abundance and temperature or salinity.

Short Review of the Eco-geography of Crangon

The species belonging to the genus Crangon Fabricius, 1798 only occur in the Northern Hemisphere both in Atlantic and Pacific waters. The higher number of species of Crangon in the Pacific suggests that they originated from this area. To date, a few studies have identified some common features between members of the genus, but the species have largely been ignored in taxonomic, phylogeographic, and ecological research efforts. Crangon are all carnivores or omnivores probably with a relevant ecological role; in some cases top-down control by the type species, C. crangon (Linnaeus, 1758), has been suggested. Several species live in shallow coastal waters and might represent abundant prey for fish including flatfish during their nursery period; the shrimp themselves prey upon the early life stages of flatfish. Because of their high abundance, some shrimp have commercial value not only for human consumption but also as bait. However, the taxonomic status within Crangon and genetic relationships among populations within species are still unsettled. Also, their geographic ranges and general life cycle features are poorly documented. Despite occurring only in the Northern Hemisphere, Crangon are originally temperate water species. Most have still a high upper tolerance limit but are also quite adapted to low temperatures. They might then have a high temperature tolerance range which will be beneficial in a climate change scenario. In this work we review previous investigations on the various species of Crangon across the spread of their geographic occurrence and highlight issues requiring further research.

Arachidonic acid is a Major Component in Gonadal Fatty acids of Tropical Coral Reef fish in the Philippines and Japan

The aim of the present study was to investigate the characteristics of gonadal fatty acid composition in 19 species of wild coral reef fish (Serranidae, Lutjanidae, Lethridae, Siganidae and Labridae) from Philippine (11 species of female) and Japanese (8 species of female and 5 species of male) waters with special attention to arachidonic acid (ArA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) levels and their ratios. ArA levels were always higher than EPA levels in polar lipids of all the species and in neutral lipids in 17 of the 19 species. In ovarian polar lipids of the 19 species, ArA level ranged from 6.0% to 19.4%, while EPA level ranged from 0.9% to 6.2%. Ovarian DHA level was also always higher than EPA in all the species analyzed. Consequently, ArA/EPA ratios of these species were high, unlike cold- and temperate-water species. ArA was the top fatty acid component in testis polar lipids of three Lethrinus species (21.4% to 22.9%). Thus, ArA is not a minor component, that is, the major highly unsaturated fatty acids (HUFAs) of polar lipids in all coral reef fish gonads are DHA and ArA (not EPA). The present information on gonadal fatty acid composition can be used as a guideline for advancing appropriate broodstock diets of tropical coral reef fish, emerging aquaculture commodities in developing countries.