Lipid composition of yellowtail flounder (<Emphasis Type="Italic">Limanda ferruginea</Emphasis>) in relation to dietary lipid intake

Condition indices (CI), hepatosomatic indices (HSI) and proximate, lipid and fatty acid composition of wild and laboratory-reared yellowtail flounder (Limanda ferruginea) (Storer, 1839) were compared from data taken throughout spring and summer 1996–1998. Cluster analysis was performed on the fatty acid signatures of these two groups along with a commercial diet and several invertebrate species to determine possible feeding patterns in Conception Bay, Newfoundland. HSI and levels of storage fat were significantly higher in the muscle and liver of laboratory-reared yellowtail flounder, indicating an efficient absorption of dietary lipid and an increase in fat deposition. Fatty acid analysis of the liver showed that wild fish contained significantly higher proportions of the essential fatty acids 20:46, 20:53 and 22:63; whereas proportions of 18:1 and 18:26 were significantly higher in all fractions of lipid examined from laboratory-reared fish than they were from wild fish. Polar fractions of lipid were more similar than the neutral fraction of lipid when comparing wild and laboratory-reared fish. Taken together, the differences in CI, HSI, proximate and fatty acid composition suggest that feeding commercial diets to L. ferruginea can cause changes in patterns of lipid deposition and metabolism. Cluster analysis of marine plankton, sedimenting particulate matter, wild invertebrates, the commercial diet and fish tissues showed that the fatty acid signatures of both wild and laboratory-reared yellowtail flounder closely resembled their respective food items. Fatty acid signatures from wild fish were more closely related to plankton and settling particulate matter, suggesting relatively few steps in the food web leading to yellowtail flounder. In addition to the resemblance between fatty acids in the commercial diet and the tissues of laboratory-reared yellowtail flounder, these fish had similar fatty acid signatures to those of wild invertebrates.Communicated by J.P. Grassle, New Brunswick     

Genetic evidence for hybridisation between Haliotis rubra and H. laevigata

Seventeen abalone whose appearance was intermediate between the two commonly fished species in south-eastern Australia, blacklip (Haliotis rubra) and greenlip (H. laevigata), were collected between 1986 and 1989. Protein electrophoresis revealed that rare, morphologically intermediate abalone are predominantly F₁ hybrids; others are backcross individuals. There is also evidence of possible local introgression of H. rubra genes into H. laevigata and vice versa in sympatric populations. These two species exhibit marked morphological, behavioural and genetic differences, and yet hybridisation, although rare, occurs in at least several regions of sympatry. The commonly invoked explanations for the breakdown of species barriers, environmental disturbance and rarity of one of the parent species, do not appear applicable, unless microhabitat separation creates local rarity of one species. The frequency of hybridisation is discussed in relation to regional biogeography.     

Herbivory in the gammarid amphipod Aora typica: relationships between consumption rates, performance and abundance across ten seaweed species

This paper reveals a substantial capacity for herbivory of seaweeds in the gammarid amphipod Aora typica, adults eating seven of ten taxonomically and morphologically diverse seaweed species offered to them in a no-choice assay. The green algae Ulva spathulata and Enteromorpha intestinalis were consumed at the highest rates in both no-choice (2.3–2.5 mg blotted weight individual⁻¹ day⁻¹) and multiple-choice assays (0.5–1.3 mg blotted weight individual⁻¹ day⁻¹). Adult A. typica collected from two different species of brown seaweeds had very similar feeding preferences to each other. Juvenile A. typica grew to reproductive maturity on the green algae E. intestinalis and U. spathulata, and the brown algae Carpophyllum maschalocarpum and Ecklonia radiata. In common with previous studies on members of other amphipod families, survivorship of juvenile amphipods was positively correlated with feeding preferences of adults across seaweed species (r ²=0.43, P=0.04). However, densities of A. typica on seaweeds in the field (excluding the intertidal E. intestinalis and U. spathulata) were not significantly correlated with feeding preferences of adults (r ²=0.07, P=0.5) or survivorship of juveniles (r ²=0.17, P=0.31). This suggests that either host seaweeds are not a major dietary component of these amphipods in nature, or that the host’s value as a food source is overridden by other properties such as the degree of shelter it affords from larger consumers. This study provides the first demonstration that a member of the cosmopolitan amphipod family Aoridae is capable of consuming a diverse range of seaweeds.     

The influence of application rate on the bacterial mutagenicity of soil amended with municipal sewage sludge

The mutagenic potential of two soils amended with a municipal sewage sludge at two application rates was monitored over a 2-year period using Salmonella/microsome mutagenicity assay. Samples were collected from undisturbed monolith lysimeters of Weswood sandy clay (Fluventic Ustochrept) and Padina sandy loam (Grossarenic Paleustalf) amended with dried sewage sludge at 50 and 100 Mg/ha. Soil samples were collected and sequentially extracted with methylene chloride and methanol. The residues from these extracts were tested for mutagenicity at five doses with and without metabolic activation in Salmonella strain TA98. In general, the mutagenic potential of the amended soils of both application rates for the first 8 weeks following sludge application increased and then slowly decreased. The maximum mutagenic response observed in the soil extracts was 222 revertants at a dose of 10 mg of residue. This response was induced by the methanol extract from the Weswood soil collected 56 days after the application of 50 Mg/ha sewage sludge as compared to the 100 Mg/ha application which induced 202 revertants/mg. The mutagenicity of all fractions extracted from the sludge-amended soil at both application rates collected 717 days after application were not appreciably different from extracts from the unamended soils. The data indicate that chemicals that were mutagenic in bacteria persist in the soil and that at the higher application rates, as much as 2 years may be required for the mutagenic potential of the soil to return to background levels.     

Analysis of target and nontarget pollutants in aqueous leachates from the hazardous waste site Stringfellow, California, via ion chromatography - particle beam and inductively coupled plasma mass spectrometry

Liquid chromatography particle beam mass spectrometry (PB/MS is a powerful tool for the analysis of target pollutants but complementary methods are required for nontarget compounds. Preliminary data are presented on an anion exchange chromatography PB/MS based method for the detection of the target compound 4-chlorobenzene sulfonic acid (a contamlnant found in hazardous waste leachates) and also for nontarget pollutants in aqueous leachate samples from the Stringfellow hazardous waste site in California. Anion exchange chromatography coupled to inductively coupled plasma mass spectrometry yields qualitative and quantltative elemental analysis showing the presence or absence of key heteroatoms in organic pollutants including chlorine, other halogens, phosphorus and sulfur.     

The degradation of dyestuffs: Part I Primary biodegradation under anaerobic conditions

The paper describes a method for measuring the primary biodegradability of water soluble dyestuffs under anaerobic conditions and gives the results obtained on 22 dyes of commercial significance.     

Rick-sensitive foraging in common shrews: an interruption model and the effects of mean and variance in reward rate

Summary A model of risk-sensitive foraging based on a continuously foraging but interruptable predator is developed and tested in a simple choice experiment using common shrews.Given a choice of two feeding stations, shrews behaved in accordance with the broad predictions of the model. Having been trained below their estimated food requirement, shrewss preferred the station y elding the higher mean reward rate, but prefereence for a constant (constant reward rate) or risky variable reward rate) station was influenced by experience of variance in reward rate at the risky station.Preference was influenced most clearly by experience of reward rate variance during tests rather than training.     

Coupling ecology and GIS to evaluate efficacy of marine protected areas in Hawaii.

In order to properly determine the efficacy of marine protected areas (MPAs), a seascape perspective that integrates ecosystem elements at the appropriate ecological scale is necessary. Over the past four decades, Hawaii has developed a system of 11 Marine Life Conservation Districts (MLCDs) to conserve and replenish marine resources around the state. Initially established to provide opportunities for public interaction with the marine environment, these MLCDs vary in size, habitat quality, and management regimes, providing an excellent opportunity to test hypotheses concerning MPA design and function using multiple discrete sampling units. Digital benthic habitat maps for all MLCDs and adjacent habitats were used to evaluate the efficacy of existing MLCDs using a spatially explicit stratified random sampling design. Analysis of benthic cover validated the a priori classification of habitat types and provided justification for using these habitat strata to conduct stratified random sampling and analyses of fish habitat utilization patterns. Results showed that a number of fish assemblage characteristics (e.g., species richness, biomass, diversity) vary among habitat types, but were significantly higher in MLCDs compared with adjacent fished areas across all habitat types. Overall fish biomass was 2.6 times greater in the MLCDs compared to open areas. In addition, apex predators and other species were more abundant and larger in the MLCDs, illustrating the effectiveness of these closures in conserving fish populations within their boundaries. Habitat type, protected area size, and level of protection from fishing were all important determinates of MLCD effectiveness with respect to their associated fish assemblages. Although size of these protected areas was positively correlated with a number of fish assemblage characteristics, all appear too small to have any measurable influence on the adjacent fished areas. These protected areas were not designed for biodiversity conservation or fisheries enhancement yet still provide varying degrees of protection for fish populations within their boundaries. Implementing this type of biogeographic process, using remote sensing technology and sampling across the range of habitats present within the seascape, provides a robust evaluation of existing MPAs and can help to define ecologically relevant boundaries for future MPA design in a range of locations.     

Group-living in cliff swallows as an advantage in avoiding predators

Summary Cliff swallows (Hirundo pyrrhonota) in SW Nebraska, USA, nest in colonies and associate in groups away from their colonies. The degree to which group-living in this species affords advantages in the avoiding of predators was examined. The distance from the colony at which a snake predator was detected increased with colony size. In flocks away from the colonies, group vigilance increased, but the time that each individual spent vigilant decreased, with flock size. As a result, birds in large flocks had more time for preening and mud-gathering. Cliff swallows did not effectively mob predators and thus were unable to deter predators regardless of group size. Nesting within each colony was highly synchronous, but when the effects of ectoparasites on nesting success were removed, individuals nesting during the peak breeding period were no more successful than those nesting before or after the peak. This suggests that swamping of predators is unlikely in cliff swallow colonies. Nests at the edges of colonies were more likely to be preyed upon than nests nearer the center, suggesting that colonial nesting conferred some selfish herd benefits. Overall reproductive success did not vary with colony size. While cliff swallows receive some anti-predator benefits by living in groups, the avoidance of predators is probably not a major selective force for the evolution of coloniality in this species.     

Structure and evolution of song form in the wrens Thryothorus sinaloa and T. felix

Summary The songs of two species of wrens, Thryothorus sinaloa and T. felix, are less similar than previously believed. We have found that song structure, bout patterning, and other aspects of singing behavior are widely divergent between the two species, which are sympatric over much of their ranges. The nature of these differences supports the hypothesis of contrast reinforcement in bird song. Further evidence is provided by essentially parallel differences in another pair of sympatric species, T. pleurostictus and T. maculipectus. A cluster analysis of song form of the above four species plus one other, T. ludovicianus, suggests that those species which are allopatric are the most similar in song form, while sympatric species are the most dissimilar. We relate various features of singing behavior in the two species to some aspects to their ecology, and examine relationships among various song parameters within the genus Thryothorus. The parallel differences in pairs of sympatric Thryothorus in structure of song units, temporal organization of song, and duetting, along with the close correlation of groups of song parameters in the five species of Thryothorus leads us to propose that strategies or adaptive complexes of singing characteristics may exist in the genus.