Small Freshwater Species Research Articles

Techno-economics of solar assisted drying of small freshwater fish to ensure global nutritional security

Small freshwater fishes are a sustainable source of nutrition that is often disregarded in the fishing industry. Even though dry fish sectors utilize these fishes, they often do not reach potential customers due to the time-consuming, weather-dependent traditional drying practices and the associated hygiene-related issues involved in open sun drying of small fishes. There is little to no information on the drying of small freshwater species, especially Vitamin A rich mola carplet. Therefore, the drying behavior and quality characteristics of dried molas were investigated using two available forms of solar conduction dryers – corrugated solar conduction dryer (CSCD) and corrugated electrical solar conduction dryer (CESCD) which were then compared with open sun drying (OSD). The salt and turmeric marinated fresh molas were dried to 1.12%, 4.03%, and 30.82% (d.b.) within 5 h of drying by using CESCD, CSCD, and OSD, respectively and the respective average moisture diffusivity were 12.5 × 10−9 m2/s, 9.3 × 10−9 m2/s, and 2.47 × 10−9 m2/s. The color change (ΔE) kinetics and Vitamin A degradation kinetics were also analyzed for samples dried by using both dryers. The ΔE kinetics showed the color change during drying of mola followed the zero-order kinetics model whereas, Vitamin A degradation followed first-order kinetics. The proximate analysis of key constituents such as proteins and fats showed better retention in CESCD and CSCD as compared to OSD. Economic analysis of both the dryers was used to indicate their commercial feasibility.

Does environmental enrichment affect the behaviour of fish commonly used in laboratory work?

Housing conditions can have significant effects on the behaviour and physiology of captive animals. Enriching barren environments, for example by providing structural complexity or companionship, are generally considered beneficial as they can decrease the occurrence of abnormal behaviours and physiology and as such, it is argued that enrichment helps to improve welfare for captive animals such as laboratory rodents. Fish are increasingly used in a range of laboratory contexts, yet to date there is very little information on how fish should be housed. Here, we report the results of an experiment addressing the effects of environmental enrichment on learning, memory and temperament behaviours in three-spined sticklebacks, a small freshwater species commonly used to address evolutionary and ecological questions in the laboratory. We compared the behaviours of three different treatment groups: (i) fish recently caught in a natural environment, (ii) fish housed for 10 months in enriched tanks in the laboratory, and (iii) fish housed for 10 months in plain tanks in the laboratory. We found no effect of housing environment on learning or temperament behaviours, however, there was a difference in how accurately fish retained information. Both laboratory enriched and plain fish returned to a previously rewarded location after a 3-day retention interval, but wild fish did not. Together these results indicate that the environmental enrichments provided in this laboratory setting did not generate behavioural differences in captive populations of three-spined sticklebacks.

When fish shoals meet: outcomes for evolution and fisheries

AbstractThe mechanisms underlying the social structure of free‐ranging fish shoals have received little attention in comparison to functional studies on shoaling. Recently, however, a number of investigations, both in the marine and in the freshwater environment, have begun to address the underlying mechanisms by concentrating on interactions between free‐ranging shoals. The rates of shoal encounters can influence the opportunities for individual assortment by phenotype and selection of shoal size; act as a constraint on the observed patterns of shoal structure by restricting individual choice behaviour and were found to be high in several small freshwater species (where intershoal distances were small), but lower in marine species where shoals were more dispersed. The duration of encounters may play a role in that it affects both the time available for assessment (of the encountered shoal) as well as that for exchange of individuals. Scarce published information on the outcome of shoal encounters suggests that the outcome of shoal encounters is influenced by shoal composition but not by shoal size. Individual behaviour may have evolved to maintain shoal size when shoals encounter, but when fish populations are depleted by fishing, this trait can exacerbate range and stock collapse. Furthermore, an understanding of the dynamics of shoal encounters has important consequences for the evolution of reciprocal altruism and the transmission of information through social learning within populations. Finally, information on encounter rates between shoals and the number of individuals that are exchanged on such occasions could be important for making predictions about the spread of disease through fish populations.

Zebrafish: bridging the gap between development and disease.

The zebrafish has been the model of choice amongst developmental biologists for many years. This small freshwater species offers many advantages to the study of organ and tissue development that are not provided by other model systems. Against this background, modern molecular genetic approaches are being applied to expand the physical and genetic mapping of the zebrafish genome. These approaches complement the large-scale mutagenic screens that have led to the isolation of mutant phenotypes. Some of the phenotypes have been found to resemble human disease states, while mapping and sequencing data have revealed zebrafish genes with significant homology to human disease-causing genes. It is the realization that the zebrafish offers an amenable system for understanding disease, as opposed to development, that underpins this review. The adventitious identification of disease phenotypes amongst zebrafish mutants and the important area of deliberate disease modelling using transgenesis and gene targeting should lead to a better application of the zebrafish as a vertebrate model of human diseases.

Transformation of fish cells and embryos.

AbstractFish are the largest group of vertebrates. They have diverse features to adapt to a wide variety of environments, which make them excellent models for studies in various areas, including molecular and cellular biology (1,2). Small freshwater species, such as medaka (Oryzias latipes) and zebrafish (Brachydanio rerio) are being studied in a growing number of laboratories because of their advantages as experimental animals (2,3). The procedures for the preparation and maintenance of fish cell cultures do not differ from those of higher vertebrates. In general, fish cells grow in the same medium as mammalian cells and can be preserved by standard methods for freezing. A specific feature of fish cells is that they generally proliferate over a wide range of temperatures, and the optimal growth temperature reflects the environment that each species inhabits (4,5). In addition, fish cells are thought to be naturally immortal. Even cells derived from nonneoplastic tissues can grow continuously (6–8).KeywordsLong Terminal RepeatTransformation EfficiencyFish CellTransgenic FishHerpes Simplex Virus Thymidine KinaseThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

On Gigantic Land-Tortoises and a small Freshwater Species from the Ossiferous Caverns of Malta, together with a List of their Fossil Fauna; and a Note on Chelonian Remains from the Rock-cavities of Gibraltar

The Maltese fossil remains described in this memoir were collected by Admiral Spratt, C.B., and myself in various ossiferous deposits in the island. A few of the bones have been referred to in a note I communicated to the Geological Society in 1866. Having now, however, for the first time had an opportunity of comparing the reptilian remains from the Zebbug Cavern with my own gatherings (in consequence of the collection made by Admiral Spratt having been lately presented to the British Museum), I find the combined assemblage of Chelonian remains display so many features of interest that I have no hesitation in laying the details before the Society. The singular characters of the associated Proboscidian, Rodentian, and Avian relics have been already described; so that, with the exception of the Hippopotami , this contribution may be said to complete the palæontographical portion of the explorations up to the termination of my researches in 1865. The following specimens are contained in the Museum of the Society and in the British Museum. I am indebted to T. C. Archer, Esq., Director of the Museum of Science and Art, Edinburgh, for his kindness in lending me the typical skeleton of Testudo ephippium of Günther, to compare with the Maltese remains; and my best thanks are also due to Dr. Günther, F.R.S., for his assistance in the determination of a few of the specimens. Although Dr. Falconer recognized Chelonian bones and fragments of shields in Admiral Spratt's collection, I can find in his writings