Search

Intraspecific biodiversity among populations is ecologically and evolutionarily notable. Substantial adaptations in well-studied commercial species should be obvious and ought to have been uncovered. The tenet of marine stability posits relatively little local adaptation in the sea, except for temperature responses to latitude for widespread species. However, aquatic reproduction is tightly constrained by water chemistry, which may lead to abstruse adaptations. Capelin (Mallotus villosus) reproduction has been studied for over a century, occurring within pebble substrate on beaches or the seafloor of continental shelves. Offshore spawners (Iceland/Barents Sea) have embryos with tolerance of high salinity. I provide new and historical data on beach spawners from several areas indicating that their embryos perform well from ~2 to 28 psu, but at higher salinities indicative of coastal seawater, there is poor hatch success, larvae take longer to hatch, hatch at a smaller size, and starve more quickly. The body of evidence supports the hypothesis that beach spawning evolved from anadromy, with offshore spawning a derived state, enabled by increased salinity tolerance. The results have recovery implications for depleted Newfoundland stocks, which have been spawning seasonally late under relatively high salinity for over 25 years. La biodiversite intraspecifique entre populations est un phenomene notable sur le plan tant de l'ecologie que de revolution. Les adaptations importantes chez des especes d'interet commercial bien etudiees devraient etre evidentes et avoir deja ete decouvertes. L'hypothese de la stabilite marine prevoit relativement peu d'adaptation locale dans la mer, outre des reactions a la temperature associees a la latitude pour les especes a grande aire de repartition. La chimie de l'eau exerce toutefois un controle serre sur la reproduction aquatique, ce qui peut mener a des adaptations obscures. La reproduction du capelan (Mallotus villosus), etudiee depuis plus d'un siecle, a lieu dans des substrats caillouteux sur les plages ou sur le fond marin de plateformes continentales. Les embryons d'individus qui frayent au large (Islande/mer de Barents) sont tolerants a de fortes salinites. Je presente des donnees nouvelles et historiques sur des individus frayant sur des plages de plusieurs endroits, qui indiquent que leurs embryons vont bien dans la fourchette de ~2 a 28 psu, mais a de plus fortes salinites caracteristiques d'eaux marines littorales, le succes d'eclosion est faible, les larves prennent plus de temps a eclore, sont plus petites au moment de l'eclosion et meurent de faim plus rapidement. Les preuves disponibles supportent l'hypothese voulant que le frai sur la plage soit une evolution decoulant de l'anadromie, le frai au large etant un etat derive rendu possible par une augmentation de la tolerance a la salinite. Ces resultats sont importants pour la comprehension du retablissement de stocks terre-neuviens decimes qui, depuis plus de 25 ans, frayent tard dans la saison dans des conditions de salinite relativement elevee. [Traduit par la Redaction], Introduction Within species, local adaptation among populations often occurs when sufficient reproductive isolation, selective pressures, and heritability are present. This intraspecific biodiversity is important both evolutionary and ecologically. Local adaptation [...]

Abstract: This study documents temporal changes in abundance and prevalence of larval anisakid nematodes in two commercially important fish; the vermilion rockfish Sebastes miniatus, and the ocean whitefish Caulolatilus princeps, [...]

Starvation periods are common for many animals, including fish, birds, and mammals. Many fish species exhibit extraordinary resilience to prolonged starvation, but the reasons for that and the mechanisms employed during these periods are poorly understood. This study shows that similar to mammals and birds, many fish species undergo three phases during starvation: (I) a short transient phase, (II) a long, protein conservation steady state phase with mainly fat oxidation as the primary energy source, and (III) a shift to protein mobilization as a main energy source. These starvation states and their transitions were quantified by a meta-analysis of large empirical data available in the literature, revealing that low critical levels of fat reserves trigger the transition to the third state. The critical fat level, denoted as γ (percentage of total lipid in body mass), ranges between 0.7% and 5%, depending on the species. It appears that these transitions in the energy mobilization phases are regulated by hormonal changes, including growth hormone (GH), leptin, cortisol, and ghrelin, but the exact mechanisms are still unclear and should be further investigated. Simulations in silico of starvation periods at various temperatures using a dynamic model indicated that temperature affects the length of Phase II because of changes in protein metabolism, with consequences on the ability to withstand prolonged starvation. Les periodes de famine sont repandues chez de nombreux animaux, dont les poissons, les oiseaux et les mammiferes. Si de nombreuses especes de poissons presentent cependant une resilience remarquable en situation de famine prolongee, les causes de cette resilience et les mecanismes employes durant ces periodes ne sont pas bien compris. L'etude demontre que, comme chez les mammiferes et les oiseaux, la famine chez de nombreuses especes de poissons compte trois phases, a savoir (I) une courte phase transitoire, (II) une longue phase stationnaire de conservation des proteines, l'oxydation des lipides etant alors la principale source d'energie, et (III) le passage a la mobilisation des proteines comme principale source d'energie. Ces etats de la famine et leurs transitions ont ete quantifies par une metaanalyse d'un grand nombre de donnees empiriques publiees, qui revele que l'atteinte d'un niveau minimum critique des reserves de lipides declenche la troisieme phase de la famine. Le niveau critique de lipides, designe γ (pourcentage de la masse du corps constitue par les lipides totaux), varie de 0,7 % a 5 %, selon l'espece. Il semble que les transitions d'une phase de mobilisation de l'energie a une autre soient controlees par des changements hormonaux, notamment de l'hormone de croissance (GH), de la leptine, du cortisol et de la ghreline, mais les mecanismes qui interviennent dans ce processus demeurent meconnus et doivent faire l'objet d'etudes plus poussees. Des simulations in silico de periodes de famine a differentes temperatures a l'aide d'un modele dynamique indiquent que la temperature a une incidence sur la duree de la phase II en raison de modifications du metabolisme des proteines et de leurs consequences sur la capacite de resister a la famine prolongee. [Traduit par la Redaction], Introduction Periods of food deprivation is common in nature for many animals, but few species can withstand prolonged starvation in a manner that fish can (see a general review by [...]

Abstract: The out-of-phase population oscillations between anchovy and sardine have been attributed to climate changes. However, the biological processes causing these species alternations have remained unresolved. Here we propose a [...]

Abstract: We examined a 36-year record of concurrent midwater trawl and water quality sampling conducted during fall to evaluate habitat trends for three declining fish species in the San Francisco [...]

Abstract: Using over 20 years of annual spawner survey data collected from 46 natural populations of coastal Oregon coho salmon (Oncorhynchus kisutch), we examined large-scale spatial and temporal dynamics of [...]

Abstract: The fecundity of European plaice (Pleuronectes platessa) in the Irish Sea between 2000 and 2004 was estimated during the spawning season for fish in the three main spawning areas [...]

This study focuses on the population dynamic effects of a pulse disturbance (a toxic algal bloom in the early Summer of 1988) on cod (Gadus morhua) populations along the Skagerrak coast of Norway. For this purpose, we applied 'intervention analysis' (sensu G. E. P. Box and G. C. Tiao). For the marine system studied, we estimated that the 1988 bloom killed 42-81% of the 0-group (6-mo-old) cod before the fall of the same year (with an average effect estimated to be ~60%). The algal bloom had no detectable direct harmful effect on the 1-group cod (during the same fall) but was found to have a delayed effect (from 58% to 99%) on the survival of the 0-group (in 1988) to the 1-group (in 1989). We concluded that the bloom had no long-term effect on the cod. Our analysis is presented as a case study using intervention analysis within the field of ecology. Assuming the availability of both a credible ecological model and a long-term observational time series (as was the case for our marine system), we suggest that intervention analysis provides a valuable tool for simultaneously studying the unperturbed dynamical structure and the impact of the environmental disturbances. Key words: algal blooms; cod; ecological perturbations; Gadus morhua; intervention analysis; Norwegian coast; population dynamics; pulse disturbance; Skagerrak; times series modeling; toxic algae.

EPIZOOTIOLOGY OF COLUMNARIS DISEASE IN AQUACULTURE AND SPORT FISHING PONDS LOCATED WITHIN A BOUNDED HYDROLOGIC SYSTEM HAITHAM H. MOHAMMED AND COVADONGA R. ARIAS, SCHOOL OF FISHERIES, AQUACULTURE, AND AQUATIC SCIENCES, [...]

Europe is set to quash a precedent-setting initiative designed to tackle a disturbing side effect of common drugs--their impact on aquatic life. Nature has learned that landmark regulations intended to [...]