Can cost–benefit analysis explain fish distribution patterns?

This review describes some recent theoretical and empirical research into the way fish respond to spatial heterogeneity in their environment, and particularly to patchily distributed resources. The ways in which the need to acquire food interacts with other important requirements such as thermoregulation and predator avoidance to determine space use are considered, as are interactions with other members of the same species, viewed both as shoaling companions and as competitors. Recent developments in ideal free theory are discussed and the extent to which this formulation can explain how fish distribute themselves among feeding patches is examined. The implications of overtly aggressive interactions, in the form of dominance hierarchies and territorial systems, for distribution patterns in the laboratory and in the field are also reviewed. Finally the extent to which cost–benefit analysis can help to explain fish distribution patterns and the relative importance of behavioural processes compared to other determinants of the distribution of fish are considered.     

Aspects of reproduction and their implications for the conservation of the endangered limpet,Patella ferruginea

Summary

The protandric limpet, Patella ferruginea G., is the most endangered marine species in the Western Mediterranean and is at serious risk of extinction. Nevertheless, its biology and ecology are little known. In the present work, several reproductive aspects are studied. Recruitment take place in June and the largest individuals are the most scarce. The sex ratio is slanted towards the largest sizes, and the species seems to show sex change at sizes from 60 mm upwards, although males can be observed up to 80 mm. There is no correlation between size of oocytes and shell length; however, the larger females contribute greatly to the reproductive event, with high fecundity and GSI values. The mean diameter of oocytes was observed to be 149.78 μm, whereas the heads of spermatozoa were 3.78 μm long. The results of the present study increase the maximum length for males by double that cited in previous literature and highlight the importance of strictly protecting females (i.e., most of the largest individuals, >60 mm), since their population percentage is very low, in order to develop adequate strategies to preserve the species.     

Feeding Responses of Hatchery-Reared Gilthead Sea Bream (Sparus aurata L.) to a Commercial Diet and Natural Prey Items

Many fish species have evolved feeding mechanisms and behaviours enabling them to feed on specific prey. However, such mechanisms may not be optimal for feeding on commercial-pelleted diets in aquaculture. Gilthead sea bream chew and occasionally eject pellets or parts of pellets from the mouth when feeding on commercial diets. This may result in an increase in nutritional waste from the intensive culture of this species. In this study we examined the prevalence of this food processing behaviour in two sizes of sea bream, feeding on three types of natural prey items in comparison to a commercial pellet, to give an insight into the circumstances in which excess chewing and ejection of food items from the mouth occurred. These included two hard-textured food items (commercial pellet and hard-shelled prey) and two soft-textured food items (larvae and small crustacean). Both sizes of sea bream frequently consumed the soft-textured food types, however large sea bream also frequently consumed hard-textured pellets. Hard-textured food required longer handling times and elicited more chewing and the ejection of food items from the mouth. These results suggest that future investigations on the food processing behaviour and consequent waste when fed commercial diets differing in texture could give an insight into improving diets and feeding efficiency for intensively cultivated gilthead sea bream.     

Geographical variation in size in the European rabbit Oryctolagus cuniculus (Lagomorpha: Leporidae) in western Europe and North Africa

Craniometric data of nine characters from 260 skulls of Oryctolagus cuniculus from western Europe and northern Africa were gathered to examine phenotypic variation in size, using both univariate and multivariate analyses. Although animals from the northern part of Europe were found to be larger than those from southern Europe, variation in size occurred in a continuous cline. Skull size was positively correlated with latitude and negatively correlated with ambient temperature. On the basis of skull morphology, there is no evidence for separation of O. cuniculus into the two or more subspecies commonly described. Further data, particularly from genetic material, are required to clarify the taxonomic status of the rabbit in Europe.     

Fish can show emotional fever: stress-induced hyperthermia in zebrafish

Whether fishes are sentient beings remains an unresolved and controversial question. Among characteristics thought to reflect a low level of sentience in fishes is an inability to show stress-induced hyperthermia (SIH), a transient rise in body temperature shown in response to a variety of stressors. This is a real fever response, so is often referred to as ‘emotional fever’. It has been suggested that the capacity for emotional fever evolved only in amniotes (mammals, birds and reptiles), in association with the evolution of consciousness in these groups. According to this view, lack of emotional fever in fishes reflects a lack of consciousness. We report here on a study in which six zebrafish groups with access to a temperature gradient were either left as undisturbed controls or subjected to a short period of confinement. The results were striking: compared to controls, stressed zebrafish spent significantly more time at higher temperatures, achieving an estimated rise in body temperature of about 2–4°C. Thus, zebrafish clearly have the capacity to show emotional fever. While the link between emotion and consciousness is still debated, this finding removes a key argument for lack of consciousness in fishes.     

Implications of domestication and rearing conditions for the behaviour of cultivated fishes

Farmed fishes are often selectively bred for desirable production traits, such as rapid growth, that brings with them behavioural differences. In addition, the striking differences in the environment experienced by wild and cultured fishes offers considerable scope both for unplanned, natural selection for different inherited behavioural phenotypes and for behavioural differences arising from differential experience. In this paper, the evidence that such processes have produced behavioural differences between wild and cultured fishes is reviewed in relation to feeding, antipredator responses, aggression and reproductive behaviour. The reported findings are discussed in relation to the concept of 'behavioural syndromes', or suites of co‐varying behavioural traits that adapt individuals of the same population to spatial and temporal variation in selection regimes. The implications of the behaviour of cultured fishes for their welfare in production cages, for the environmental impact of escapees on wild stocks and for the success of hatchery‐based restocking programmes are considered. The review inevitably concentrates on salmonids, in which such phenomena have been intensively researched.     

Environmental controls over carbon exchange of three forest ecosystems in eastern China

Net ecosystem productivity (NEP) was continuously measured using the eddy covariance (EC) technique from 2003 to 2005 at three forest sites of ChinaFLUX. The forests include Changbaishan temperate mixed forest (CBS), Qianyanzhou subtropical coniferous plantation (QYZ), and Dinghushan subtropical evergreen broad‐leaved forest (DHS). They span wide ranges of temperature and precipitation and are influenced by the eastern Asian monsoon climate to varying extent. In this study, we estimated ecosystem respiration (RE) and gross ecosystem productivity (GEP). Comparison of ecosystem carbon exchange among the three forests shows that RE was mainly determined by temperature, with the forest at CBS exhibiting the highest temperature sensitivity among the three ecosystems. The RE was highly dependent on GEP across the three forests, and the ratio of RE to GEP decreased along the North–South Transect of Eastern China (NSTEC) (i.e. from the CBS to the DHS), with an average of 0.77 ± 0.06. Daily GEP was mainly influenced by temperature at CBS, whereas photosynthetic photon flux density was the dominant factor affecting the daily GEP at both QYZ and DHS. Temperature mainly determined the pattern of the interannual variations of ecosystem carbon exchange at CBS. However, water availability primarily controlled the interannual variations of ecosystem carbon exchange at QYZ. At DHS, NEP attained the highest values at the beginning of the dry seasons (autumn) rather than the rainy seasons (summer), probably because insufficient radiation and frequent fog during the rainy seasons hindered canopy photosynthesis. All the three forest ecosystems acted as a carbon sink from 2003 to 2005. The annual average values of NEP at CBS, QYZ, and DHS were 259 ± 19, 354 ± 34, and 434 ± 66 g C m⁻² yr⁻¹, respectively. The slope of NEP that decreased with increasing latitude along the NSTEC was markedly different from that observed on the forest transect in the European continent. Long‐term flux measurements over more forest ecosystems along the NSTEC will further help verify such a difference between the European forest transect and the NSTEC and provide insights into the responses of ecosystem carbon exchange to climate change in China.     

Three‐spined sticklebacks Gasterosteus aculeatus as a model for exploring behavioural biology

Niko Tinbergen chose the three‐spined stickleback Gasterosteus aculeatus for his classic behavioural studies because they are small, robust, common and easy to house in the laboratory under reasonably natural conditions and also because their behaviour, while sufficiently simple to be tractable, is still sufficiently complex to be interesting. An analysis of citation records shows that this was an inspired choice. Research on these small fish has addressed all four of Tinbergen's famous questions (causation, development, functions and evolution) and has contributed to the understanding of many different behavioural systems. The G. aculeatus literature is used here to explore several themes in fundamental behavioural biology (diet choice, shoaling, behavioural syndromes and sexual signalling) and the extent to which research using G. aculeatus has informed both fundamental and applied behavioural biology, the latter in the context of aquaculture research.