Oceanic environmental factors affecting the activity of rabbitfish Siganus fuscescens around Jogashima, Kanagawa, Japan

Variations in the level of quality and extractive nitrogenous components were investigated in the fresh muscle and commercial dried products of rabbitfish Siganus fuscescens collected from Penghu, Taiwan. The respective freshness quality for fresh muscle is as follows: trimethylamine oxide (TMAO), 29.50 mg N/100 g; trimethylamine (TMA), 2.30 mg N/100 g; NH3, 6.61 mg/100 g; total volatile basic nitrogen (TVBN), 13.32 mg/100 g; aerobic plate count, 1.53 log CFU/g; and K-value, 28.80%. The respective freshness quality for dried products is as follows: TMAO, 43.44 mg N/100 g; TMA, 25.56 mg N/100 g wet wt.; NH3, 52.00 mg/100 g wet wt.; TVBN, 149.98 mg/100 g; aerobic plate count, 4.16 log CFU/g; and K-value, 89.73%. The major fatty acids in the fresh muscle and dried products are C16:0, C18:1 n-9, C18:0, C16:1 C22:6 n-3, and C22:5 n-3. The major nucleotide compound is inosine 5ʹ-monophosphate (IMP) in the fresh muscle (68%) and hypoxanthine (Hx) in the dried products (79%). The level of total free amino acids in the dried products shows significant variation depending on the processing method of the plants.

Three Acanthocephala species were recovered and identified from three species of fish host. They are Neoechinorhynchus agilis collected from grey mullet, (Mugil cephalus), Neorhadinorhynchus macrospinosus from rabbit fish (Siganus fuscescens), and Rhadinorhynchus pristis from spotted mackerel (Scomber australasicus). All are new locality records. Scanning electron microscopy and light microscopy were used to describe the morphological characters. In addition, these three acanthocephalans were characterized genetically using a molecular approach. The nuclear ribosomal DNA region spanning the first internal transcribed spacer (ITS-1), the 5.8S gene and the second internal transcribed spacer (ITS-2) was amplified and the sizes of PCR products derived were different in length. They are 450 bp for N. agilis, 800 bp for N. macrospinosus, and 600 bp for R. pristis.

: We studied the potential utilization of rabbit fish (Siganus fuscescens) meat in textured products. We examined the gel-forming ability of rabbit fish caught between July 2001 and August 2002 off the coast of Nagasaki. Fish obtained from approximately July to September (during the spawning season and immediately after), had low gel-forming ability. Fish caught in winter or spring showed high elastic gel formation. Washing of meat with fresh water was found to be important for gel formation. It was concluded that rabbit fish meat has a high gel-forming ability and, therefore, that rabbit fish meat is suitable for textured food production except during the spawning season.

Rising temperatures and extreme climate events are propelling tropical species into temperate marine ecosystems, but not all species can persist. Here, we used the heatwave-driven expatriation of tropical Black Rabbitfish (Siganus fuscescens) to the temperate environments of Western Australia to assess the ecological and evolutionary mechanisms that may entail their persistence. Population genomic assays for this rabbitfish indicated little genetic differentiation between tropical residents and vagrants to temperate environments due to high migration rates, which were likely enhanced by the marine heatwave. DNA metabarcoding revealed a diverse diet for this species based on phytoplankton and algae, as well as an ability to feed on regional resources, including kelp. Irrespective of future climate scenarios, these macroalgae-consuming vagrants may self-recruit in temperate environments and further expand their geographic range by the year 2100. This expansion may compromise the health of the kelp forests that form Australia’s Great Southern Reef. Overall, our study demonstrates that projected favourable climate conditions, continued large-scale genetic connectivity between populations, and diet versatility are key for tropical range-shifting fish to establish in temperate ecosystems.

Establishing levels of functional redundancy in browsing fish populations among sampling periods and across spatial gradients is important in understanding coral reef functioning. We used baited video techniques to determine functional redundancy and variability in browsing herbivores within no-take marine protected areas (MPAs) and reference fished sites across two sampling periods and four reef types (scaling from high to low coral cover) in Moreton Bay, Australia (~27°S, 153°E). We hypothesised higher herbivore abundance and browsing rates in MPAs due to protection from fishing, but lower functional redundancy in Moreton Bay generally than in tropical reefs. The function of Sargassum browsing in Moreton Bay is conducted by a single species (rabbitfish Siganus fuscescens), which is unlikely to browse at ecologically significant rates. Siganus fuscescens abundance was variable between reef types, sampling periods and individual sites, such that their abundance and browsing rates were not higher within MPAs. Similar spatial and temporal variability was found for fish community structure, indicating that other functional roles might not be influenced by MPA protection in Moreton Bay. We highlight the importance of accounting for variability in fish communities and ecosystem processes across spatial and temporal periods in considering the influence of no-take MPAs.

The rabbitfish Siganus fuscescens is an economically valuable species that is widely distributed throughout the estuaries, intertidal, and offshore coasts of the Indo-Pacific and eastern Mediterranean. Ten novel microsatellite loci from the genome of S. fuscescens were developed using the fast isolation protocol with amplified fragment length polymorphism of sequences containing repeats. Polymorphisms in these 10 microsatellite markers were determined from 32 wild individuals. The number of alleles per locus and the polymorphism information content ranged from 2 to 5 and from 0.059 to 0.668, respectively. The observed and expected heterozygosities varied from 0.063 to 0.781 and from 0.062 to 0.731, respectively. Although 1 locus (LZY-X7, P < 0.005) showed significant deviation from the Hardy-Weinberg equilibrium, no deviations were detected in the other 9 loci. These microsatellite loci may be useful for further population genetic studies, conservation studies, population structure assessment, and linkage map construction of S. fuscescens.

To explore the potential utility of underutilized fish in the fish sauce industry, fish sauces were prepared from both raw and heat-induced meat of Japanese anchovy Engraulis japonica and rabbit fish Siganus fuscescens using wheat malt, and their quality aspects and sensory properties were assessed. Proximate composition of the fish meat represents protein as the major component (16.0–17.8%), other than moisture. Analyses of free amino acids, peptides including oligopeptides, and organic acids contents in fish sauces revealed suitability of both raw and heat-induced meat of the selected species in commercial fish sauce production. The variations in taste of raw meat fish sauces were species-specific, but the taste of fish sauces from heat-induced meat were similar.

The fish assemblage structure response to rapid degradation of Enhalus acoroides seagrass beds due to overgrazing by green sea turtles (Chelonia mydas) was investigated at Iriomote Island, southern Japan, by visual censusing of fish species in several microhabitats in and around the beds (i.e., dense seagrass bed, grazed bed, their boundaries, and adjacent sandy area). Fish assemblage structure differed among the seagrass microhabitats, both species and individual numbers being higher in microhabitats with seagrass compared to overgrazed beds and unvegetated sandy areas, together with different species composition. In the dense seagrass beds and boundary areas (the border area between dense seagrass beds and grazed areas), seagrass-associated fishes such as the rabbit fish Siganus fuscescens and cardinal fish Ostorhinchus ishigakiensis were abundant and comparable with those in other seagrass beds in the area. In addition, the fish assemblages in those microhabitats varied seasonally, fish abundance being greater in summer due to higher levels of recruitment. In the grazed bed, benthic gobies, such as Ctenogobiops crocineus and Cryptocentrus caeruleomaculatus, were dominant (similarly so in unvegetated sandy areas), and seasonal variations in such assemblages were relatively low compared to those in dense seagrass microhabitats. The decrease in the abundance and diversity of seagrass-associated fish in the grazed areas could be explained partly by the shortage of vegetation (< 20 cm in leaf length) for shelter and feeding throughout the year. The results suggested that the degradation of seagrass beds due to overgrazing by green turtles has a deleterious effect on fish assemblages, and that future conservation and management strategies for seagrass beds should consider both their associated fish communities and green turtles.

A training strategy for enhancing prediction accuracy of high magnitude oceanic environmental factors based on deep learning model

Bioimaging tools reveal copper processing in fish cells by mitophagy

Summary Catch, fishing effort and yield estimates of the Cape Bolinao reef flat fishery in Lingayen Gulf, Philippines are provided, based on data collected from May 1987 to April 1988. The dynamics of the dominant species, the rabbitfish Siganus fuscescens, suggest that such fisheries are capable of maintaining a high production in site of heavy fish in pressure. However, yield comparisons with those of other reef fisgeries in the Indo-Pacific region, along with characteristics of the catch and the use of multiple gear types, suggest that current extraction rates should not be increased.

Global warming is facilitating the range expansion of tropical herbivores, causing a tropicalization of temperate marine ecosystems, where tropical herbivores can suppress habitat‐forming macrophytes, supporting the resilience of canopy‐free ecosystem states. However, currently we lack a thorough understanding of the mechanisms that, on one hand, support the persistence of tropical herbivores and on the other support the recovery of temperate foundation species in tropicalized ecosystems, a required knowledge to predict potential regime shifts and reversals to the baseline state of the ecosystem. This study tested processes behind the persistence of the tropicalization of temperate reefs which experienced a complete loss of their kelp forests and an influx of tropical herbivores following a marine heatwave in 2011. For this, we assessed the feedback mechanisms that maintain turf‐dominated states (recruitment of tropical herbivores, browsing and grazing rates and turf cover) and those that resist it (kelp recruitment, survival and reproductiveness). We found that the reefs remained tropicalized with high abundances of turf and tropical herbivores after 9 years from the regime shift. The rabbitfish Siganus fuscescens and the chub Kyphosus bigibbus were the most important herbivores whose persistence was supported by the adjacent reef lagoon, where seagrass meadows and the backreef habitats hosted juveniles of both species, particularly rabbitfish. Tropical herbivores exerted a strong top–down control on turf seaweed and kelp during herbivory assays, rapidly consuming kelp individuals in open areas. However, in topographical refuges in the reefs, herbivory was low and kelp individuals survived, with some having reproductive tissue. Synthesis. Our findings incorporate the importance of nursery grounds for tropical herbivores and herbivory refugia for kelp individuals into the tropicalization model, where the former increases the resilience of canopy‐free states and the latter might facilitate recovering kelp populations. The restoration of abundant warm‐resistant kelp populations in shelters could provide local sources of propagules to recolonize open spaces; however, our results suggest that the reduction of herbivory and the provision of turf‐free substratum would be necessary to boost the recovery of kelp forests.

Laboratory experiments were conducted in a recirculating flow tank to evaluate the effects of waves on herbivory by the Rabbitfish Siganus fuscescens. rabbitfish (27 cm FL) increased feeding on the kelp Ecklonia cava or Eisenia bicyclis in a faster oscillating flow with a seasonally increased appetite. When feeding activity was highest, oscillating flow reduced feeding to 50% at the velocity amplitude of 1.1 m/s and to nil at ca 1.5 m/s. Swimming speeds observed in different fish sizes suggested that the upper velocity limit for feeding increased little for larger fish. The results and the wave-induced water velocity predictions indicate that destructive feeding by rabbitfish on kelp is very unlikely to be inhibited by waves on the Pacific coast of central Honshu.

Effects of Waves and Temperature on Feeding by the Rabbitfish Siganus Fuscescens on Kelps Eisenia Bicyclis and Ecklonia cava

Cholera is one of a number of infectious diseases that appears to be influenced by climate, geography and other natural environments. This study analysed the environmental factors of the spatial distribution of cholera in China. It shows that temperature, precipitation, elevation, and distance to the coastline have significant impact on the distribution of cholera. It also reveals the oceanic environmental factors associated with cholera in Zhejiang, which is a coastal province of China, using both remote sensing (RS) and geographical information systems (GIS). The analysis has validated the correlation between indirect satellite measurements of sea surface temperature (SST), sea surface height (SSH) and ocean chlorophyll concentration (OCC) and the local number of cholera cases based on 8-year monthly data from 2001 to 2008. The results show the number of cholera cases has been strongly affected by the variables of SST, SSH and OCC. Utilizing this information, a cholera prediction model has been established based on the oceanic and climatic environmental factors. The model indicates that RS and GIS have great potential for designing an early warning system for cholera.