This study compared sea lice (Lepeophtheirus salmonis) infestation rates on juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon in five nearshore areas of the British Columbia coast selected on the basis of proximity to salmon farms. A 10-week study in the Broughton Archipelago found sea lice were 8.8 times more abundant on wild fish near farms holding adult salmon and 5.0 times more abundant on wild fish near farms holding smolts than in areas distant from salmon farms. We found that 90% of juvenile pink and chum salmon sampled near salmon farms in the Broughton Archipelago were infected with more than 1.6 lice·(g host mass)–1, a proposed lethal limit when the lice reach mobile stages. Sea lice abundance was near zero in all areas without salmon farms. Salinity and temperature differences could not account for the higher infestation rates near the fish farms. The most immature life stages dominated the lice population throughout the study, suggesting the source of lice was a stationary, local salmonid population. No such wild population could be identified. The evidence from this control–impact study points to a relationship between salmon farms and sea lice on adjacent, wild, juvenile salmon.

No abstract

Successful application of fish-revival techniques in commercial fishing prior to release of nontarget species requires clear evidence that recovery devices do indeed improve physiological status and minimize postcapture delayed mortality. This study provides such evidence for a newly designed recovery box (Fraser box) that assisted gill ventilation. Immediately after capture by gillnet, adult coho salmon (Oncorhynchus kisutch) were in a state of severe metabolic exhaustion and stress, based on a comprehensive analysis of plasma and muscle tissue. However, when placed in a Fraser recovery box for 1-2 h, both lethargic and vigorous fish showed significant metabolic recovery and their ability to swim was also quickly restored. An emphatic demonstration of the benefit of the Fraser box was the successful revival of >90% of fish that appeared dead at capture. Furthermore, postcapture delayed mortality was only 2.3% after a 24-h observation period. Therefore, in the context of commercial salmon gillnet fishing, revival of nontarget coho salmon in a Fraser box, in combination with a soak time (total time the gillnet is in the water) £ 70 min and careful fish handling to minimize physical trauma, could improve physiological status, restore swimming ability, and markedly reduce postcapture delayed mortality. Farrell et al.Résumé : Pour que l'application de techniques de réanimation de poissons non-ciblés avant leur rejet à l'eau lors de pêches commerciales soit un succès, il faut s'assurer que les moyens de rétablissement améliorent de fait la condition physiologique et minimisent la mortalité différée après la capture. Notre étude fournit une telle assurance dans le cas de l'utilisation d'une enceinte de rétablissement récemment conçue (la boîte de Fraser) qui favorise la ventilation des branchies. Immédiatement après leur capture au filet maillant, les Saumons coho adultes (Oncorhynchus kisutch) sont en état d'épuisement métabolique et de stress, comme l'indique une analyse détaillée du plasma et du tissu musculaire. Cependant, après 1-2 h dans la boîte de rétablissement de Fraser, tant les poissons léthargiques que les poissons vigoureux font preuve d'un rétablissement métabolique significatif et retrouvent rapidement leur capacité de nage. Une démonstration significative de l'efficacité de la boîte de Fraser est que plus de 90 % des poissons qui semblaient morts à la capture s'y sont rétablis avec succès. De plus, la mortalité différée après la capture était de seulement 2,3 % après une période d'observation de 24 h. Dans le cas de la pêche commerciale au saumon à l'aide de filets maillants, la réanimation des Saumons coho non ciblés par la pêche, combinée à un temps de mouillage des filets de £ 70 min et une manutention soignée des poissons de façon à minimiser les traumatismes physiques, peut donc améliorer la condition physiologique, rétablir la capacité de nage et réduire de façon marquée la mortalité différée.[Traduit par la Rédaction] 1946

No abstract

We use the so-called "bent-cable" model to describe natural phenomena that exhibit a potentially sharp change in slope. The model comprises two linear segments, joined smoothly by a quadratic bend. The class of bent cables includes, as a limiting case, the popular piecewise-linear model (with a sharp kink), otherwise known as the broken stick. Associated with bent-cable regression is the estimation of the bend-width parameter, through which the abruptness of the underlying transition may be assessed. We present worked examples and simulations to demonstrate the regularity and irregularity of bent-cable regression encountered in finite-sample settings. We also extend existing bent-cable asymptotics that previously were limited to the basic model with known linear slopes of 0 and 1. Practical conditions on the design are given to ensure regularity of the full bent-cable estimation problem if the underlying bend segment has nonzero width. Under such conditions, the least-squares estimators are shown to be consistent and to asymptotically follow a multivariate normal distribution. Furthermore, the deviance statistic (or the likelihood ratio statistic, if the random errors are normally distributed) is shown to have an asymptotic chi-squared distribution.