Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

Human impacts on the world's oceans have been substantial, leading to concerns about the extinction of marine taxa. We have compiled 133 local, regional and global extinctions of marine populations. There is typically a 53-year lag between the last sighting of an organism and the reported date of the extinction at whatever scale this has occurred. Most disappearances (80%) were detected using indirect historical comparative methods, which suggests that marine extinctions may have been underestimated because of low-detection power. Exploitation caused most marine losses at various scales (55%), followed closely by habitat loss (37%), while the remainder were linked to invasive species, climate change, pollution and disease. Several perceptions concerning the vulnerability of marine organisms appear to be too general and insufficiently conservative. Marine species cannot be considered less vulnerable on the basis of biological attributes such as high fecundity or large-scale dispersal characteristics. For commercially exploited species, it is often argued that economic extinction of exploited populations will occur before biological extinction, but this is not the case for non-target species caught in multispecies fisheries or species with high commercial value, especially if this value increases as species become rare. The perceived high potential for recovery, high variability and low extinction vulnerability of fish populations have been invoked to avoid listing commercial species of fishes under international threat criteria. However, we need to learn more about recovery, which may be hampered by negative population growth at small population sizes (Allee effect or depensation) or ecosystem shifts, as well as about spatial dynamics and connectivity of subpopulations before we can truly understand the nature of responses to severe depletions. The evidence suggests that fish populations do not fluctuate more than those of mammals, birds and butterflies, and that fishes may exhibit vulnerability similar to mammals, birds and butterflies. There is an urgent need for improved methods of detecting marine extinctions at various spatial scales, and for predicting the vulnerability of species.

Extinction vulnerability in marine populations

Morphometric tools for landmark data: geometry and biology

Human beings may affect the welfare of fish through fisheries, aquaculture and a number of other activities. There is no agreement on just how to we igh the concern for welfare of fish against the hum an interests involved, but ethical frameworks exist th at suggest how this might be approached. Different definitions of animal welfare focus on an animal's condition, on its subjective experience o f that condition and/or on whether it can lead a natu ral life. These provide different, legitimate, pers pectives, but the approach taken in this paper is to focus on welfare as the absence of suffering. An unresolved and controversial issue in discussion s about animal welfare is whether non-human animals exposed to adverse experiences such as physical injury or confinement experience what humans would call suffering. The neocortex, which in huma ns is an important part of the neural mechanism tha t generates the subjective experience of suffering, i s lacking in fish and non-mammalian animals, and it has been argued that its absence in fish indicates that fish cannot suffer. However, a strong alternative view is that complex animals with sophisticated behaviour, such as fish, probably have the capacity for suffer ing, though this may be different in degree and kind fro m the human experience of this state. Recent empirical studies support this view and show that painful stimuli are, at least, strongly avers ive to fish. Consequently, injury or experience of othe r harmful conditions is a cause for concern in term s of welfare of individual fish. There is also growing e vidence that fish can experience fear-like states a nd that they avoid situations in which they have experience d adverse conditions.

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Current issues in fish welfare

The thyroid hormones (THs), thyroxine (T4) and triiodothyronine (T3) are products of the thyroid gland in all vertebrates. Their role in early development and metamorphosis is well established in mammals and amphibians, respectively, and recently several studies in fish have highlighted the importance of THs during flatfish metamorphosis. THs are present in high quantities in fish eggs and are presumably of maternal origin. During embryogenesis the concentration of T4 and T3 in the eggs decrease until endogenous production starts. Thyroid hormone receptors (TR) have been isolated from several teleosts and in common with tetrapods two receptor isoforms have been identified, TRα and TRβ. Both the receptors are expressed in early embryos and larvae of the Japanese flounder (Paralichthys olivaceus), zebrafish (Danio rerio) and seabream (Sparus aurata) although a different temporal pattern is apparent. The role of THs and TRs in fish embryogenesis, larval development and during metamorphosis will be discussed.

Thyroid hormones in growth and development of fish

Skeletal descriptors and quality assessment in larvae and post-larvae of wild-caught and hatchery-reared gilthead sea bream (Sparus aurata L. 1758)

Normal and abnormal osteological development of caudal fin in Sparus aurata L. fry

Data on the concentrations of some blood constituents of captive Adriatic sturgeon, Acipenser naccarii, a primitive bony fish, are reported. Serum osmolality, Na+, K+, Cl−, Ca2+, cortisol, glucose and total protein concentrations were measured. The effects of anaesthesia, temperature, crowding and prolonged handling stress were tested on a group of 12 4-year-old sturgeons sampled repeatedly. The anaesthetic dose of MS 222 (140 mg l−1) induced significant osmolality elevation in the sturgeon. After exposure to colder temperature (17 versus 25°C), cortisol and Cl− concentrations significantly decreased. The cultured sturgeon did not seem susceptible to crowding and prolonged handling stress, since neither the serum cortisol and glucose levels nor the other blood parameters were affected by these stressors. Results are compared with the few available data on other chondrostean fish and with those on teleosts.

Serum parameters of adriatic sturgeon acipenser naccarii (pisces : acipenseriformes) : effects of temperature and stress

Extracting fish size using dual underwater cameras

Abnormalities of shape or color and bony I body deformities whether related to lack of
swimbladder or not, are still a major problem for many Mediterranean finfish sea farms.
Despite their high economical consequences, they remain difficult to eliminate, due to basic
gaps of knowledge about their causes and sometimes management errors in the rearing
technique.
After a review of abnormalities in aquaculture, the authors targeted the mechanisms of their
apparition and aimed to the main gaps of knowledge and the possible solutions. Until accurate
cost effective conditions for prevention are found, strategies of early assessment and sorting
are recommended. The role of the EU research in these actions is emphasized.

Stefano Cataudella

Papers

Skeletal descriptors and quality assessment in larvae and post-larvae of wild-caught and hatchery-reared gilthead sea bream (Sparus aurata L. 1758)

Normal and abnormal osteological development of caudal fin in Sparus aurata L. fry

Serum parameters of adriatic sturgeon acipenser naccarii (pisces : acipenseriformes) : effects of temperature and stress

Extracting fish size using dual underwater cameras

Abnormalities in finfish mariculture: An overview of the problem, causes and solutions.