Fatty acid profiles of juvenile salmon indicate prey selection strategies in coastal marine waters

Juvenile salmon exhibit high growth rates upon their arrival into the marine environment. Dietary changes from freshwater and estuarine habitats to those derived from the marine environment may play an important role in ultimate adult survival. We measured the total lipid and fatty acid (FA) composition of juvenile Chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), and 18 of their potential prey items sampled from coastal waters during their first few months at sea. Coho salmon had significant reductions in their lipid content (% wet weight) between May and June, likely due to early marine growth. We did not find a significant drop between May and June Chinook salmon lipid content, which may indicate an earlier ontogenetic selection to marine prey that are higher in lipids and essential fatty acids (EFAs). Juvenile salmon ate prey of both high and low lipids. Significant FA compositional changes occurred for both coho and Chinook salmon between May and June. In May, the FA profile of juvenile salmon, especially coho salmon, did not resemble their prey items; however, in June, there was a strong correlation between salmon and their common fish prey as determined by gut content analysis. Significant increases in the level of EFAs, especially docosahexaenoic acid (DHA, 22:6n-3) accounted for the majority of the monthly differences in salmon tissue FA composition. In order for juvenile salmon to adequately meet their physiological requirements, they may have adapted to select advantageous prey with higher levels of EFAs, especially DHA, in order to rapidly increase their growth and ultimate survival.     

The dual nature of money: why monetary systems matter for equitable bioeconomy

Environmental Economics and Policy Studies - Money can be understood from an individual perspective as an abstract form of wealth. From a communal perspective, however, money is better regarded as...     

Spatial overlap and trophic interactions between pelagic fish and large jellyfish in the northern California Current

Recent studies have indicated that populations of gelatinous zooplankton may be increasing and expanding in geographic coverage, and these increases may in turn affect coastal fish populations. We conducted trawl surveys in the northern California Current and documented a substantial biomass of scyphomedusae consisting primarily of two species (Chrysaora fuscescens and Aurelia labiata). Spatial overlap of these jellyfish with most pelagic fishes, including salmon, was generally low, but there were regions of relatively high overlap where trophic interactions may have been occurring. We compared feeding ecology of jellyfish and pelagic fishes based on diet composition and found that trophic overlap was high with planktivorous species that consume copepods and euphausiid eggs such as Pacific sardines (Sardinops sagax), northern anchovy (Engraulis mordax), Pacific saury (Cololabis saira), and Pacific herring (Clupea pallasi). Moreover, isotope and diet analyses suggest that jellyfish occupy a trophic level similar to that of small pelagic fishes such as herring, sardines and northern anchovy. Thus jellyfish have the potential, given their substantial biomass, of competing with these species, especially in years with low ecosystem productivity where prey resources will be limited.     

The role of fairness in implementing large-scale change: Employee evaluations of process and outcome in seven facility relocations

Organizational transitions may be difficult to implement if employees resist the change. ‘Participation’ and ‘education’ (Kotter and Schlesinger, 1979) are hypothesized to enhance commitment to change, however mechanisms for those effects are unclear. In a sample of employees from seven relocated organizations, a test of our model showed that the effects of justification (a form of education) on intent to remain are mediated by outcome and procedural fairness judgements. Voice (a form of participation) showed no effects on fairness judgments, perhaps because employees did not expect voice in relocation decisions. Supplementary analyses yielded no evidence for direct effects of voice and justification on intention to remain. The findings extend our understanding of fairness to transition settings.     

Embedded wisdom or rooted problems? Aid workers' perspectives on local social and political infrastructure in post‐tsunami Aceh

This paper analyses the role of local social, cultural, and political institutions in post‐disaster reconstruction projects. It contends that such institutions are important considerations within community‐driven reconstruction initiatives, but are often viewed with ambivalence by external aid organisations. This paper draws upon in‐depth qualitative interviews with aid workers involved in the post‐tsunami reconstruction in Aceh, Indonesia, to establish: (i) what roles community institutions were suited to play in the reconstruction; (ii) what were the limitations of community institutions when engaging with external aid agencies; (iii) how did external aid agencies engage with local community institutions; and (iv) how did external aid agencies perceive community institutions.     

Modeling phosphorus concentrations in Irish rivers using land use, soil type, and soil phosphorus data

Modeling diffuse phosphorus (P) loss may indicate management strategies to minimize P loss from agricultural sources. An empirical model predicting flow-weighted phosphorus concentrations (MRP) was derived using data collected from 35 Irish river catchments. Monitoring records of riverine P and stream flow data were used to calculate MRP values averaged for the years 1991-1994. These data were modeled using land use, soil type, and soil P data. Soil type in catchments was described using soil survey classifications weighted according to their P desorption properties from laboratory results. Soil test P concentrations for the studied watersheds were obtained from a national database. Soil P levels were weighted based on the results of field experiments measuring P losses in overland flow from fields at different soil test P levels. The 35 catchments were statistically clustered into two populations (A and B) based on differences in soil type, specifically, soil hydrology. Catchments in Cluster A had predominantly poorly drained soils and comparatively higher MRP concentrations (0.03-0.17 mg L(-1)) than Cluster B areas (0.01-0.7 mg L(-1)) with mostly well-drained soils. Regression equations derived for A and B type catchments predicted MRP values with 68 and 62% of the variation explained in the models, respectively. Data extracted for the rest of the country were applied to the models to delineate areas at risk on a national scale. While the models were only moderately accurate they highlighted the influence of land management, specifically, high production grassland receiving high P inputs, in conjunction with the effect of soil type and soil hydrology on the transport of P to surface waters.     

The effects of sand movement on intertidal seaweeds and selected invertebrates at Bound Rock,New Hampshire,USA

A seasonal study of sand movement and the benthic intertidal organisms at Bound Rock, New Hampshire, USA was conducted between November, 1973 and February, 1975. The site is subjected to irregular sand fluctuations, as well as diurnal, neapspring and major summer sand intrusions. The abundance and distribution of intertidal species was interrelated with the historical sand fluctuations at the area. For example, the lower limits of Mytilus edulis, Balanus balanoides and Porphyra umbilicalis approximated the highest summer sand elevations. Highly abraded rock surfaces in the lower intertidal zone were dominated by opportunistic annuals (e.g. Enteromorpha spp.) and perennial psammophytic or sand-loving seaweeds (e.g. Ahnfeltia plicata and Sphacelaria radicans). Overall, the intertidal seaweed populations at Bound Rock showed a lower number of perennials and fewer species than adjacent rocky shores. The low species diversity of seaweeds at the study site is attributable to unstable environmental conditions and a limited number of habitats. Even so, several psammophytic microhabitats are evident at Bound Rock depending upon the extent of sand burial and abrasion. The morphological and reproductive adaptations of several psammophytic species are discussed.Published with the approval of the Director of the New Hampshire Agricultural Experiment Station as Scientific Contribution No. 812.Scientific Contribution No. 53 of the Jackson Estuarine Laboratory.     

The maturation and breeding biology of Harmothoë imbricata (Polychaeta: Polynoidae)

The embryos of Harmothoë imbricata (L.) are protected during their early development as a mass under the scales of the female parent. Eggs are shed into the space under the scales through nephridial papillae which elongate and turn dorsally as the female matures. The mass is held together by an adhesive layer surrounding each egg. Maturation begins in September and breeding occurs during March and April, when each female spawns twice in succession. Males contain mature sperm throughout the breeding season and shed only a small proportion at each spawning. As the polychaetes mature, pairs are formed with the male resting on the dorsal surface of the female. When the female spawns, the male sheds sperm over the egg mass and the two animals then separate. The sperm has a long acrosome to penetrate the adhesive layer around the egg. Embryo-protecting species in other groups of polychaeces show parallel specialization in sperm structure and in breeding behaviour. A chronology has been established for the development of embryos up to their release from the parent, and this can be used to estimate the spawning date of females with embryo masses collected on the shore. Individuals grow at widely varying rates after settlement on the shore, and no year classes could be detected in the population. All individuals spawn in the first spring after settlement, and at least some survive to spawn again in one or more subsequent springs.