The relation between daily food intake and growth of the Pacific mangrove prawn Palaemon debilis Dana and its Atlantic relative Palaemon elegans Rathke, both from the Gulf of Elat

The behaviour and distribution of Palaemon debilis Dana was studied in mangrove lagoons along the east coast of Sinai. Food intake and growth of this prawn were measured in the laboratory and compared with the related Atlantic species Palaemon elegans Rathke, occuring in a saltwater fishpond at Elat. Daily food intake was similar in both species and correlated with their metabolic weight. By feeding groups of prawns different rations of prawnmeat during fourteen days the daily maintenance ration was estimated as approximately 14 percent of the metabolic dry weight while the net food conversion was estimated as 0.4. The role of Palaemon debilis in the mangrove toodweb is discussed

Combatting disability discrimination: a comparison of France and Great Britain

This article examines disabled people’s employment in Great Britain and France. Although both countries have poor rates of employment for disabled people compared to non-disabled people, Great Britain’s disabled people’s employment rate is lower than France’s. Possible explanations include weak enforcement mechanisms in Great Britain, British judicial resistance, the lack of an institutional role for British trade unions resulting in an implementation gap and the proactive form of French law, a quota-levy scheme, which has no British parallel. The conclusions suggest which of these explanations are the most plausible and propose that Great Britain considers adopting some French provisions, thus tempering Britain’s voluntarist approach

Environmental variables, habitat discontinuity and life history shaping the genetic structure of Pomatoschistus marmoratus

Coastal lagoons are semi-isolated ecosystems exposed to wide fluctuations of environmental conditions and showing habitat fragmentation. These features may play an important role in separating species into different populations, even at small spatial scales. In this study, we evaluate the concordance between mitochondrial (previous published data) and nuclear data analyzing the genetic variability of Pomatoschistus marmoratus in five localities, inside and outside the Mar Menor coastal lagoon (SE Spain) using eight microsatellites. High genetic diversity and similar levels of allele richness were observed across all loci and localities, although significant genic and genotypic differentiation was found between populations inside and outside the lagoon. In contrast to the FST values obtained from previous mitochondrial DNA analyses (control region), the microsatellite data exhibited significant differentiation among samples inside the Mar Menor and between lagoonal and marine samples. This pattern was corroborated using Cavalli-Sforza genetic distances. The habitat fragmentation inside the coastal lagoon and among lagoon and marine localities could be acting as a barrier to gene flow and contributing to the observed genetic structure. Our results from generalized additive models point a significant link between extreme lagoonal environmental conditions (mainly maximum salinity) and P. marmoratus genetic composition. Thereby, these environmental features could be also acting on genetic structure of coastal lagoon populations of P. marmoratus favoring their genetic divergence. The mating strategy of P. marmoratus could be also influencing our results obtained from mitochondrial and nuclear DNA. Therefore, a special consideration must be done in the selection of the DNA markers depending on the reproductive strategy of the species

The interrelation between temperature regimes and fish size in juvenile Atlantic cod (Gadus morhua): effects on growth and feed conversion efficiency

The present paper describes the growth properties of juvenile Atlantic cod (Gadus morhua) reared at 7, 10, 13 and 16 °C, and a group reared under “temperature steps” i.e. with temperature reduced successively from 16 to 13 and 10 °C. Growth rate and feed conversion efficiency of juvenile Atlantic cod were significantly influenced by the interaction of temperature and fish size. Overall growth was highest in the 13 °C and the T-step groups but for different reasons, as the fish at 13 °C had 10% higher overall feeding intake compared to the T-step group, whereas the T-step had 8% higher feeding efficiency. After termination of the laboratory study the fish were reared in sea pens at ambient conditions for 17 months. The groups performed differently when reared at ambient conditions in the sea as the T-step group was 11.6, 11.5, 5.3 and 7.5% larger than 7, 10, 13 and 16 °C, respectively in June 2005. Optimal temperature for growth and feed conversion efficiency decreased with size, indicating an ontogenetic reduction in optimum temperature for growth with increasing size. The results suggest an optimum temperature for growth of juvenile Atlantic cod in the size range 5–50 g dropping from 14.7 °C for 5–10 g juvenile to 12.4 °C for 40–50 g juvenile. Moreover, a broader parabolic regression curve between growth, feed conversion efficiency and temperature as size increases, indicate increased temperature tolerance with size. The study confirms that juvenile cod exhibits ontogenetic variation in temperature optimum, which might partly explain different spatial distribution of juvenile and adult cod in ocean waters. Our study also indicates a physiological mechanism that might be linked to cod migrations as cod may maximize their feeding efficiency by active thermoregulation

Listening In on the Past: What Can Otolith δ18O Values Really Tell Us about the Environmental History of Fishes?

Oxygen isotope ratios from fish otoliths are used to discriminate marine stocks and reconstruct past climate, assuming that variations in otolith δ18O values closely reflect differences in temperature history of fish when accounting for salinity induced variability in water δ18O. To investigate this, we exploited the environmental and migratory data gathered from a decade using archival tags to study the behaviour of adult plaice (Pleuronectes platessa L.) in the North Sea. Based on the tag-derived monthly distributions of the fish and corresponding temperature and salinity estimates modelled across three consecutive years, we first predicted annual otolith δ18O values for three geographically discrete offshore sub-stocks, using three alternative plausible scenarios for otolith growth. Comparison of predicted vs. measured annual δ18O values demonstrated >96% correct prediction of sub-stock membership, irrespective of the otolith growth scenario. Pronounced inter-stock differences in δ18O values, notably in summer, provide a robust marker for reconstructing broad-scale plaice distribution in the North Sea. However, although largely congruent, measured and predicted annual δ18O values of did not fully match. Small, but consistent, offsets were also observed between individual high-resolution otolith δ18O values measured during tag recording time and corresponding δ18O predictions using concomitant tag-recorded temperatures and location-specific salinity estimates. The nature of the shifts differed among sub-stocks, suggesting specific vital effects linked to variation in physiological response to temperature. Therefore, although otolith δ18O in free-ranging fish largely reflects environmental temperature and salinity, we counsel prudence when interpreting otolith δ18O data for stock discrimination or temperature reconstruction until the mechanisms underpinning otolith δ18O signature acquisition, and associated variation, are clarified

Feeding Behaviour, Swimming Activity and Boldness Explain Variation in Feed Intake and Growth of Sole (Solea solea) Reared in Captivity

The major economic constraint for culturing sole (Solea solea) is its slow and variable growth. The objective was to study the relationship between feed intake/efficiency, growth, and (non-) feeding behaviour of sole. Sixteen juveniles with an average (SD) growth of 2.7 (1.9) g/kg0.8/d were selected on their growth during a 4-week period in which they were housed communally with 84 other fish. Selected fish were housed individually during a second 4-week period to measure individual feed intake, growth, and behaviour. Fish were hand-fed three times a day during the dark phase of the day until apparent satiation. During six different days, behaviour was recorded twice daily during 3 minutes by direct observations. Total swimming activity, frequency of burying and of escapes were recorded. At the beginning and end of the growth period, two sequential behavioural tests were performed: “Novel Environment” and “Light Avoidance”. Fish housed individually still exhibited pronounced variation in feed intake (CV = 23%), growth (CV = 25%) and behavior (CV = 100%). Differences in feed intake account for 79% of the observed individual differences in growth of sole. Fish with higher variation in feed intake between days and between meals within days had significantly a lower total feed intake (r = −0.65 and r = −0.77) and growth. Active fish showed significantly higher feed intake (r = 0.66) and growth (r = 0.58). Boldness during both challenge tests was related to fast growth: (1) fish which reacted with a lower latency time to swim in a novel environment had significantly higher feed intake (r = −0.55) and growth (r = −0.66); (2) fish escaping during the light avoidance test tended to show higher feed intake (P<0.1) and had higher growth (P<0.05). In conclusion, feeding consistency, swimming activity in the tank, and boldness during behavioral tests are related to feed intake and growth of sole in captivity

Scavenger communities and fisheries waste : North Sea discards support 3 million seabirds, 2 million fewer than in 1990

Every year fisheries discard >10 million tonnes of fish. This provides a bounty for scavengers, yet the ecological impact of discarding is understudied. Seabirds are the best-studied discard scavengers and fisheries have shaped their movement ecology, demography and community structure. However, we know little about the number of scavenging seabirds that discards support, how this varies over time or might change as stocks and policy change. Here, we use a Bayesian bioenergetics model to estimate the number of scavenging birds potentially supported by discards in the North Sea (one of the highest discard-producing regions) in 1990, around the peak of production, and again after discard declines in 2010. We estimate that North Sea discards declined by 48% from 509,840 tonnes in 1990 to 267,549 tonnes in 2010. This waste had the potential to support 5.66 (95% credible intervals: 3.33-9.74) million seabirds in the 1990s, declining by 39% to 3.45 (1.98-5.78) million birds by 2010. Our study reveals the potential for fishery discards to support very large scavenging seabird communities but also shows how this has declined over recent decades. Discard bans, like the European Union's Landing Obligation, may reduce inflated scavenger communities, but come against a backdrop of gradual declines potentially buffering deleterious impacts. More work is required to reduce uncertainty and to generate global estimates, but our study highlights the magnitude of scavenger communities potentially supported by discards and thus the importance of understanding the wider ecological consequences of dumping fisheries waste.Publisher PDFPeer reviewe

Debating the Desirability of New Biomedical Technologies: Lessons from the Introduction of Breast Cancer Screening in the Netherlands

Health technology assessment (HTA) was developed in the 1970s and 1980s to facilitate decision making on the desirability of new biomedical technologies. Since then, many of the standard tools and methods of HTA have been criticized for their implicit normativity. At the same time research into the character of technology in practice has motivated philosophers, sociologists and anthropologists to criticize the traditional view of technology as a neutral instrument designed to perform a specific function. Such research suggests that the tools and methods of more traditional forms of HTA are often inspired by an ‘instrumentalist’ conception of technology that does not fit the way technology actually works. This paper explores this hypothesis for a specific case: the assessments and deliberations leading to the introduction of breast cancer screening in the Netherlands. After reconstructing this history of HTA ‘in the making’ the stepwise model of HTA that emerged during the process is discussed. This model was rooted indeed in an instrumentalist conception of technology. However, a more detailed reconstruction of several episodes from this history reveals how the actors already experienced the inadequacy of some of the instrumentalist presuppositions. The historical case thus shows how an instrumentalist conception of technology may result in implicit normative effects. The paper concludes that an instrumentalist view of technology is not a good starting point for HTA and briefly suggests how the fit between HTA methods and the actual character of technology in practice might be improved

Common Sole Larvae Survive High Levels of Pile-Driving Sound in Controlled Exposure Experiments

In view of the rapid extension of offshore wind farms, there is an urgent need to improve our knowledge on possible adverse effects of underwater sound generated by pile-driving. Mortality and injuries have been observed in fish exposed to loud impulse sounds, but knowledge on the sound levels at which (sub-)lethal effects occur is limited for juvenile and adult fish, and virtually non-existent for fish eggs and larvae. A device was developed in which fish larvae can be exposed to underwater sound. It consists of a rigid-walled cylindrical chamber driven by an electro-dynamical sound projector. Samples of up to 100 larvae can be exposed simultaneously to a homogeneously distributed sound pressure and particle velocity field. Recorded pile-driving sounds could be reproduced accurately in the frequency range between 50 and 1000 Hz, at zero to peak pressure levels up to 210 dB re 1µPa2 (zero to peak pressures up to 32 kPa) and single pulse sound exposure levels up to 186 dB re 1µPa2s. The device was used to examine lethal effects of sound exposure in common sole (Solea solea) larvae. Different developmental stages were exposed to various levels and durations of pile-driving sound. The highest cumulative sound exposure level applied was 206 dB re 1µPa2s, which corresponds to 100 strikes at a distance of 100 m from a typical North Sea pile-driving site. The results showed no statistically significant differences in mortality between exposure and control groups at sound exposure levels which were well above the US interim criteria for non-auditory tissue damage in fish. Although our findings cannot be extrapolated to fish larvae in general, as interspecific differences in vulnerability to sound exposure may occur, they do indicate that previous assumptions and criteria may need to be revised