Advances in marine biology最新文献

Bycatch and discards are a significant issue for global fisheries, with discards considered unnecessary mortality and wasted fishing. Discards have declined due to more selective gear and changes in regulations, but data on discard rates and species remains challenging to collect. Addressing discards is crucial to minimize food waste and increase seafood production. We provide an up-to-date overview of research on wasted fishing through bycatch and discards since 2012, including pots/traps, trawls, gillnets, and lines. By highlighting the challenges of collecting data on discard rates, species, and reasons, we emphasize the need for an adaptive approach to monitoring and reducing discards. Our review provides an important update on the current state of research on wasted fishing and highlights ongoing knowledge gaps in this area, indicating a need for continued efforts towards sustainable fisheries management.

Here we review the literature on the basking shark (Cetorhinus maximus, Gunnerus, 1765), well known as the second largest extant shark (and fish) species globally. Previous reviews were published by Kunzlik in 1988 and Sims in 2008, but in the last 15 years modern electronic and DNA sequencing technologies have resulted in considerable advances in our knowledge of the species' behaviour and ecology. Basking sharks are planktivores and under appropriate conditions spend prolonged periods at the ocean surface feeding on copepod prey that primarily make up their diet, the behaviour that gave rise to their common name. In general, they are migratory and move into higher latitude waters during the summer months, when loose surface-feeding aggregations may form at favoured sites, the best known of which at present occur at hotspots on the west coasts of Britain and Ireland. The species is found circumglobally in temperate waters, but they are also now known on occasion to migrate at depth between northern and southern hemispheres, as well as across oceans within the northern hemisphere. In the past basking shark were more abundant across much of their range, but, consequent on targeted fisheries and in some places intentional eradication, became everywhere scarce, with recent population recovery in the north-east Atlantic being the result of protective measures initiated in the 1990s. Despite their charismatic nature, some of their most fundamental biological processes including copulation, gestation and birth remain largely unknown, due to their migratory and often deep-water lifestyle. In contrast, the deployment of small-scale archival and satellite tags has revealed the details of both broadscale migratory movements and horizontal and vertical foraging behaviours. Recent genetic studies support evidence suggesting a degree of site fidelity in relation to seasonal feeding grounds, which likely explains why in the past local populations have collapsed following periods of intensive fishing. Other recent research using aerial drones and towed cameras has revealed within loose feeding aggregations elements of social behaviour that may have a courtship function as well as enhance feeding efficiency.

The two Kogia species, the pygmy sperm whale (K. breviceps) and the dwarf sperm whale (K. sima), have similar morphological and biological features as well as diets. Both species are deep divers, and both have wide distributions from tropical to warm-temperate zones. Although K. breviceps is larger than K. sima, there are few reports of habitat differentiation between the two species. The distribution of K. breviceps is concentrated in higher-latitudes, and this species dives deeper than K. sima. We investigated whether these two species differ in their population structures in the western North Pacific. Using stranded specimens from Japan, we compared the population genetic patterns of the two Kogia species using mtDNA control region variation (941 bp). In total, 34 K. breviceps samples and 54 K. sima samples from stranded individuals around Japan were successfully sequenced. Thirty haplotypes were detected in K. breviceps and 34 in K. sima, indicating high genetic diversity for both. Almost all these haplotypes are unique to the western North Pacific, but did not constitute distinct phylogeographic clades within either species. We detected differences between the species in the shape of haplotype networks and in the potential time of population expansion, indicating that the western North Pacific population of the two biologically similar species could have different population demographies. This may reflect differences in evolutionary histories and in the details of their ecological niches.

The scientific community is often asked to predict the future state of the environment and, to do so, the structure (biodiversity) and the functions (ecosystem functioning) of the investigated systems must be described and understood. In his "handful of feathers" metaphor, Charles Darwin explained the difference between simple and predictable systems, obeying definite laws, and complex (and unpredictable) systems, featured by innumerable components and interactions among them. In order not to waste efforts in impossible enterprises, it is crucial to ascertain if accurate predictions are possible in a given domain, and to what extent they might be reliable. Since ecology and evolution (together forming "natural history") deal with complex historical systems that are extremely sensitive to initial conditions and to contingencies or 'black swans', it is inherently impossible to accurately predict their future states. Notwithstanding this impossibility, policy makers are asking the community of ecological and evolutionary biologists to predict the future. The struggle for funding induces many supposed naturalists to do so, also because other types of scientists (from engineers to modellers) are keen to sell predictions (usually in form of solutions) to policy makers that are willing to pay for them. This paper is a plea for bio-ecological realism. The "mission" of ecologists and evolutionary biologists (natural historians) is not to predict the future state of inherently unpredictable systems, but to convince policy makers that we must live with uncertainties. Natural history, however, can provide knowledge-based wisdom to face the uncertainties about the future. Natural historians produce scenarios that are of great help in figuring out how to manage our relationship with the rest of nature.

Sponges are ecologically important benthic organisms with many important functional roles. However, despite increasing global interest in the functions that sponges perform, there has been limited focus on how such functions will be impacted by different anthropogenic stressors. In this review, we describe the progress that has been made in our understanding of the functional roles of sponges over the last 15 years and consider the impacts of anthropogenic stressors on these roles. We split sponge functional roles into interactions with the water column and associations with other organisms. We found evidence for an increasing focus on functional roles among sponge-focused research articles, with our understanding of sponge-mediated nutrient cycling increasing substantially in recent years. From the information available, many anthropogenic stressors have the potential to negatively impact sponge pumping, and therefore have the potential to cause ecosystem level impacts. While our understanding of the importance of sponges has increased in the last 15 years, much more experimental work is required to fully understand how sponges will contribute to reef ecosystem function in future changing oceans.

In the pygmy sperm whale (Kogia breviceps, Blainville 1838), vibrissae are present in neonates, but within a few months the hairs are lost, and the structures remain as empty vibrissal crypts (VCs). In this work, we have studied histologically the facial vibrissal follicles of two juveniles and one adult specimens stranded dead. A few VCs with no visible hairs were found grouped in a row rostral to each eye. The follicular lumen, covered by a simple squamous epithelium, showed invaginations in the most superficial part. Beneath the epithelium, the follicle walls were made of loose connective tissue and were encircled by a thick capsule of dense connective tissue. In juveniles, a dermal papilla was found basally and, from it, a non-keratinized pseudo hair grew upwards but did not reach the skin surface. The VCs were richly innervated and irrigated. Many lamellated corpuscles were identified in the subluminal connective tissue of the crypt walls. A large venous cavernous plexus was located beneath and around the hair papilla. The main differences observed in the adult specimen were the degeneration and calcification of both the dermal papilla and the pseudo hair, and the absence of the venous cavernous plexus, albeit maintaining a rich vascularization and innervation. Our study revealed that VCs of the pygmy sperm whale possess features of fully functional sensory structures, with a microanatomy different from those described in other species. In addition, they undergo a postnatal morphological transformation, which implies functional differences between the VCs of neonates and adults.

Little is known about the biology of pygmy (Kogia breviceps) and dwarf (K. sima) sperm whales as these animals are difficult to observe in the wild. However, both species strand frequently along the South African, Australian and New Zealand coastlines, providing samples for these otherwise inaccessible species. The use of DNA samples from tissue and DNA extracted from historical material, such as teeth and bone, allowed a first analysis of the population structure of both species in the Southern Hemisphere. A 279 base pair consensus region of the mitochondrial cytochrome b gene was sequenced for 96 K. breviceps (53 tissue and 43 teeth or bone samples) and 29 K. sima (3 tissue and 26 teeth or bone samples), and 26 and 12 unique haplotypes were identified, respectively. K. breviceps showed a higher nucleotide diversity of 0.82% compared to 0.40% in K. sima. Significant genetic differentiation was detected in the Southern Hemisphere between K. breviceps from South Africa and New Zealand (Ф_ST = 0.042, p < 0.05). Mitochondrial control region sequences (505 bp) were available for 44 individuals (41 K. breviceps and 3 K. sima) for comparative purposes. A comprehensive global phylogenetic analysis (maternal lineage) of our sequences together with all available Kogia mtDNA sequences largely supported previously published phylogenetic findings, but highlighted some changed inferences about oceanic divergences within both species. The higher nucleotide diversity and low population differentiation observed in K. breviceps may result from its broad foraging ecology and wide distribution, which may indicate a more opportunistic feeding behaviour and tolerance towards a larger range of water temperatures than K. sima.

The diets of pygmy (Kogia breviceps) and dwarf (K. sima) sperm whales in Japanese waters are poorly known. We report new information on the diets of these two species from these waters based on identifiable hard-part remains recovered from the stomach contents of 29 whales (11 pygmy and 18 dwarf sperm whales) that stranded between 1991 and 2021; those of a further two dwarf sperm whales were empty. The cephalopod (and secondarily fish and crustacean) component of the diets of these 29 whales, based on analysis of identifiable stomach-content remains, is described. The main prey includes cephalopods, represented by 1556 identifiable lower beaks (and 1483 upper beaks), crustaceans (represented by heavily digested, unidentifiable remains), and fishes (as represented by 92 otoliths). Identified prey comprises 30 species from 16 cephalopod families and 5 families from 5 fish orders. Oceanic cephalopods are the main prey of both whale species, particularly Enoploteuthis (Paraenoploteuthis) chunii and Chiroteuthis (Chirothauma) picteti. Prey diversity index values (Shannon-Weaver's diversity index H') are 2.41 for the pygmy sperm whale and 2.66 for the dwarf sperm whale. Although the main cephalopod component in the diets of these two whale species is similar, Pianka's index (0.40), a measure of niche overlap, is not that high, and may be influenced by differences in prey dominance in different feeding areas.