Entwicklung einer einfachen und schnellen Analysenmethode für Kohlenmonoxid in Fisch und Durchführung orientierender Untersuchungen

Treatment with gases containing CO, misleadingly called “tasteless smoke” or “clear smoke”, prior to freezing of fish like tuna, tilapia and swordfish (to name only a few of these species that are characterised by an intensive coloration of flesh) stabilise the fresh red colour of muscle also after thawing and suggest consumers non-existing freshness. In the European Union, carbon monoxide is excluded from being a permitted additive and therefore this handling is not allowed. Notwithstanding of the clear legal position, producers and traders are trying to establish CO treated fish on the market. In the case of taking legal measures the food control laboratories have to provide evidence that fish has been treated by CO and therefore a respective method is necessary. The method of determination of carbon monoxide in fish flesh presently applied requires considerable material and mechanistic effort to detect CO by GC after catalytic transformation into methane. The aim of our work was a direct detection of CO using suitable sensor technology. Mechanistic requirements and results of preliminary investigations to detect carbon monoxide in fish flesh will be described.

Preliminary studies on the effects of light duration on the growth and performance of Clarias gariepinus fingerlings

The effects of light duration on the growth and performance of Clarias gariepinus fingerlings were investigated using artificial methods to simulate continuous day length and absolute darkness. The normal day length (12-H Light and 12-H Darkness) served as the control. Among some of the factors affected by the varying photoperiods there were body coloration, feeding efficiency, survival rate and Specific Growth Rate (SGR). There was notably no significant difference between the SGR of the 0-photoperiod culture and the control (P>0.05) but there was significant difference between the 0-photoperiod and the 24-H photoperiod experiment (P<0.05). The haematological profile analysed showed various degrees of changes in the blood parameters of fish cultured under different photoperiods. These changes however, did not show significant differences when subjected to statistical analysis

Los fenómenos de marea roja y toxicidad de moluscos bivalvos en el Mar Argentino

Two unusual blooms of dinoflagellates appeared in the Argentine Continental Shelf in spring/summer period of 1980 and 1981, but these differed, one from the other. The first was an intense red-tide with which were associated no signs of toxicity, whereas the second, although; not showing special coloration, was associated with (and doubtless the cause of) intense toxicity in bivalves of the Gulfs of San Matías and San José and of the shelf waters off Península Valdés; the death of two fishermen was atributed to the latter. The first bloom developed as an unusual surface concentration of the predatory dinoflagellate Noctiluca scintillans. It was supposed that this concentration was produced by a particular combination of processes of circulation of water masses. The second bloom was characterizaed by high concentrations of Gonyalax excavata. Investigations at the time determined that toxins in molluscs of the area correasponded to what is called "paralytic shellfish poison". The bloom of G. excavata was associated with a front between well mixed and well stratified water masses. The maximum toxicity centre occured in the mussel bank "Constanza" (42°23'27"S and 62°45'66"W) which coincides with the front referred to above. (PDF contains 93 pages)

Genetic and morphological differences between Sebastes vulpes and S. zonatus (Teleostei: Scorpaeniformes: Scorpaenidae)

The taxonomic status of Sebastes vulpes and S. zonatus were clarified by comprehensive genetic (amplif ied fragment length polymorphisms [AFLP] and mitochondrial DNA [mtDNA] variation) and morphological analyses on a total of 65 specimens collected from a single locality. A principal coordinate analysis based on 364 AFLP loci separated the specimens completely into two genetically distinct groups that corresponded to S. vulpes and S. zonatus according to body coloration and that indicated that they are reproductively isolated species. Significant morphological differences were also evident between the two groups; 1) separation by principal component analysis based on 31 measurements, and 2)separation according to differences in counts of gill rakers and dorsal-fin spines without basal scales, and in the frequencies of specimens with small scales on the lower jaw. Restriction of gene flow between the two groups was also indicated by the pairwise ΦST values estimated from variations in partial sequences from the mtDNA control region, although the minimum spanning network did not result in separation into distinct clades. The latter was likely due to incomplete lineage sorting between S. vulpes and S. zonatus owing to their recent speciation.

Development of larval and early juvenile penpoint gunnel (Apodichthys flavidus) (family: Pholidae)

The penpoint gunnel (Apodichthys flavidus) is a member of the perciform family Pholidae. Pholids, commonly referred to as gunnels, are eel-like fishes that inhabit the rocky intertidal and subtidal regions of the northern oceans and are often associated with macroalgae, such as Fucus spp. or kelp (Watson, 1996). Gunnels are ecologically important forage fishes that form part of the diet of birds and commercially important groundfish species (Hobson and Sealy, 1985; NMFS1; Golet et al., 2000). The diet of A. flavidus and other pholids comprises primarily harpactacoid copepods, gammarid amphipods, isopods, and other crustaceans (Cross, 1981). Apodichthys flavidus ranges along the west coast of North America from southern California to the Gulf of Alaska (Mecklenburg et al., 2002). Adult A. flavidus are distinguished from other pholids by their total vertebral counts, the presence of a thick and grooved first anal spine, a preanal length that is approximately 60% standard length (SL), and a dark green to light olive coloration (Yatsu, 1981). It is one of the largest pholids (up to 46 cm) and is important in the live fish trade for both home and public aquaria (Froese and Pauly2).

Harvest History of Belugas, Delphinapterus leucas, in Cook Inlet, Alaska

Belugas, Delphinapterus leucas, in Cook Inlet, Alaska, represent a unique and isolated marine mammal population that has been hunted for a variety of purposes since prehistoric times. Archeological studies have shown that both Alutiiq Eskimos and Dena'ina Atabaskan Indians have long utilized many marine resources in Cook Inlet, including belugas. Over the past century, commercial whaling and sport hunting also occurred periodically in Cook Inlet prior to the Marine Mammal Protection Act of 1972 (MMPA). During the 1990's, the hunting mortality by Alaska Natives apparently increased to 40-70 whales per year, which led to the decling of this stock and its subsequent designation in 2000 as depleted under the MMPA. Concerns about the decline of the Cook Inlet stock resulted in a voluntary suspension of the subsistenc hunt by Alaska Natives in 1999. The difficulty in obtaining accurate estimates for the harvest of these whales is due to the inability to identify all of the hunters and, in turn, the size of the harvest. Attempts to reconstruct harvest records based on hunters' recollections and interviews from only a few households have been subject to a wide degree of speculation. To adequately monitor the beluga harvest, the National Marine Fisheries Service established marking and reporting regulations in October 1999. These rules require that Alaska Natives who hunt belugas in Cook Inlet must collect the lowere left jaw from harvested whales and complete a report that includes date and time of the harvest, coloration of the whale, harvest location, and method of harvest. The MMPA was amended in 2000 to require a cooperative agreement between the National Marine Fisheries Service and Alaska Native organizations before hunting could be resumed.

Submersible Observations on Lingcod, Ophiodon elongatus, Nesting Below 30 m off Sitka, Alaska

A research submersible was used to delineate the depth distribution of lingcod, Ophiodon elongatus, nests (egg masses) below 30 m. Although nests were not seen deeper than 97 m, behavior and dark coloration distinctive of nest-guarding lingcod were seen as deep as 126 m. Males guarding nests were distinctly colored, i.e., dark with little or no mottling, and most were obviously scarred. Two types of guarding behaviors were observed: 1) Males lying directly on or beside the nest and remaining nearly motionless unless touched and 2) males lying on a sentry post and defending the nest when other fish swam close.

Effects of socking [sic] density on ammonia excretion and the growth of Nile tilapia (Oreochromis niloticus L.)

The effects of stocking density (10, 15, 50 & 75 fish in 65L tank) and ammonia excretion on the growth of Nile tilapia, Oreochromis niloticus (12.19 ± 1.21 g) were investigated. Increasing stocking density of Nile tilapia from 15 fish/tank (2.81 g fish/L) to 75 fish/tank (14.07 g fish/L) resulted in associated increase in ammonia level (1.48 ± 0.87 mg/L to 26.44 ± 11.4 mg/L) and significantly lower growth rates. Significantly better feed conversion ratios were found for fish reared at lower (15 fish/tank) stocking densities compared to higher (75 fish/tank) stocking densities. Individual growth rates were significantly better for fish reared at a lower stocking density 15 fish/tank compared to higher stocking density 75 fish/tank and size variation (coefficient of variation in weight) were positively correlated with stocking density. Although water exchange did not have a significant effect on the growth of Nile tilapia for fish stocked at 10 fish/tank (1.88 g fish/L) and 50 fish/tank (9.38 g fish/L), however, the fish in the higher stocking density (9.38 g fish/L) groups and without water exchange, significantly changed the coloration of their bodies (silver to black) which may be due to the lower oxygen levels combined with higher ammonia levels. Ammonia level increased with increasing stocking density and without water exchange. In this study, it may be suggested that when fish reared at higher stocking densities then water exchange must be taken in to consideration so as to help avoid environmental and physiological stress to the fish.

Genetic status of selected fish taxa in relation to conservation of genetic and species diversity in the Victoria and Kyoga Lake basins

Cichlids are known for their explosive radiation especially in the African Great Lakes marked with a high level of lake endemism. These fishes have been characterized mainly along trophic and habitat differences, by variation in morphological structures such as teeth and jaws and by differences in body shape and coloration. Cichlids are important as a microcosm of macroevolution. The explosive radiation, young evolutionary scale, and the isolation of groups characterized with high levels of endemism and presence of living fossils makes the group important for evolutionary and genetic studies. Lake Victoria region cichlids which are isolated and relatively more recent in evolution were the last to be appreciated in their diversity. Recently Ole Seehausen has found scores of rock fishes in Lake Victoria which were up to then thought to be absent from the Lake and only known to occur in Lakes Malawi and Tanganyika. Greenwood put together the species groups of Lake Victoria, and later in the early 1980's revised the classification of haplochromine species to reflect the phyletic origin and interrelationship of the various groups in Lake Victoria region. Melan Stiassny has been interested in early evolution of cichlids while the likes of Paul Fuerst and Lees Kaufman and Axel Meyer have been interested and are working to explain the speciation mechanisms responsible for the explosive radiation and evolution of cichlids. Locally S.B Wandera and his student Getrude Narnulemo are spearheading the biodiversity and taxonomic studies of cichlids in Lake Victoria region

Plotosus lineatus (Thunberg, 1787)

The Striped Catfish can be recognized by its striped coloration, barbels around the mouth, and its body shape which tapers to a point posteriorly. Small juveniles are black and large adults may be less distinctly striped. Plotosus lineatus can reach a maximum length of 32 cm (13 in) and about 40cm in Persian Gulf. The body is brown with cream-colored or white longitudinal bands. The most striking feature of this species is in the fins; in fact the second dorsal, caudal and anal are fused together as in eels. In the rest of the body is quite similar to a freshwater catfish: the mouth is surrounded by four pairs of barbells, four on the upper jaw and four on the lower jaw. The first dorsal and each of the pectoral fins have a highly venomous spine. They may even be fatal. Juveniles of P. lineatus form dense ball-shaped schools of about 100 fish, while adults are solitary or occur in smaller groups of around 20 and are known to hide under ledges during the day. Adult P. lineatus search and stir the sand incessantly for crustaceans, mollusks, worms, and sometimes fish. Striped eel catfish is an oviparous fish; this species has demersal eggs and planktonic larvae. This species has evolved long ampullary canals in its electrosensory organs.