Population structure of anisakis simplex (nematoda) in harbor porpoises phocoena phocoena off Denmark

The population structure and habitat selection of Anisakis simplex in 35 harbor porpoises off Denmark are described. The nematodes were collected from the stomach and duodenal ampulla and were categorized as third-stage larvae, fourth-stage larvae, subadults, and adults. The porpoises harbored 8,043 specimens of A. simplex. The proportion of adults and subadults increased with infrapopulation size. The number of development stages across infrapopulations covaried significantly (Kendall's test of concordance). Concordance was higher in hosts with the highest intensities than in those with low and medium intensities. All stages occurred mainly in the forestomach, but this trend was stronger for the adults. Adult and subadult sex ratios did not depart significantly from 1:1. Our data suggested that recruitment and duration of each stage were the main factors accounting for infrapopulation structure. The preference of A. simplex for the forestomach conformed with previous studies, but the narrower distribution of adults relative to other stages might indicate a strategy to enhance mating opportunities. Information on sex ratios of A. simplex is scarce and contradictory. We suggest that the discrepancies might partly reflect differences in categorization criteria and statistical methods.Herreras Belled, Maria Victoria, [email protected] ; Balbuena Diaz-Pines, Juan Antonio, [email protected] ; Aznar Avendaño, Francisco Javier, [email protected] ; Raga Esteve, Juan Antonio, [email protected]

Maturation Trends Suggestive of Rapid Evolution Preceded the Collapse of Northern Cod

Northern cod, comprising populations of Atlantic cod (Gadus morhua) off southern Labrador and eastern Newfoundland, supported major fisheries for hundreds of years. But in the late 1980s and early 1990s, northern cod underwent one of the worst collapses in the history of fisheries. The Canadian government closed the directed fishing for northern cod in July 1992, but even after a decade-long offshore moratorium, population sizes remain historically low. Here we show that, up until the moratorium, the life history of northern cod continually shifted towards maturation at earlier ages and smaller sizes. Because confounding effects of mortality changes and growth-mediated phenotypic plasticity are accounted for in our analyses, this finding strongly suggests fisheries-induced evolution of maturation patterns in the direction predicted by theory. We propose that fisheries managers could use the method described here as a tool to provide warning signals about changes in life history before more overt evidence of population decline becomes manifest

Post-mortem findings and causes of death of harbour porpoises (Phocoena phocoena) stranded from 1990 to 2000 along the coastlines of Belgium and northern France

peer reviewedBetween the,ears 1990 and 2000, an attempt was made to determine the causes of death of 55 harbour porpoises stranded along the Belgian and northern French coasts. From 1990 to 1996, only five carcasses were collected as against seven in 1997, eight in 1998, 27 in 1999 and eight in 2000. The sex ratio was normal and most of the animals were juvenile. The most common findings were emaciation, severe parasitosis and pneumonia. A few cases of fishing net entanglement were observed. The main microscopical lesions were acute pneumonia, massive lung oedema, enteritis, hepatitis and gastritis. Encephalitis was observed in six cases. No evidence of morbillivirus infection was detected. Pneumonia was associated with bacteria or parasites, or both. The causes of death and the lesions were similar to those previously reported in other countries bordering the North Sea. The cause of the increased numbers of carcasses in 1999 was unclear but did not include viral epizootics or net entanglement. A temporary increase in the porpoise populatiou in the southern North Sea may have been responsible. (C) 2002 Elsevier Science Ltd. All rights reserved

Assessing the status of the cod (Gadus morhua) stock in NAFO Subdivision 3Ps in 2016

The status of the cod stock in the Northwest Atlantic Fisheries Organization (NAFO)  Subdivision 3Ps was assessed during a Fisheries and Oceans Canada (DFO) Regional Peer Review Process meeting held October 17-19, 2016. Total landings for the 2015-16 management year (April 1-March 31) were 6,427 t or just 48% of the Total Allowable Catch (TAC). This marks the sixth consecutive season that the TAC has not been fully taken. Survey abundance estimates from the DFO research vessel (RV) spring survey have been about average in recent years, whereas biomass estimates have generally been below average. Sentinel gillnet catch rates have been very low and stable since 1999. Sentinel linetrawl catch rates have been below average for the past six years and the 2015 catch rate was the lowest in the time series. Estimates of Spawning Stock Biomass (SSB) derived from a survey-based (SURBA) cohort model increased considerably over 2009-12 but have since declined. Although the stock is currently estimated to be in the Cautious Zone (18% above Blim) as defined by the DFO Precautionary Approach (PA) Framework, the probability that the stock is in the critical zone is 0.22, which is a concern. There are further concerns that the current estimate of spawning stock biomass (SSB) could be biased as the model has overestimated SSB in recent years (i.e. the assessment has been subject to downward retrospective revisions of SSB). The current SSB is very young, composed to a large extent (46%) of 4-5 year old fish. These fish are from the strong 2011 and 2012 year classes that have not yet fully matured. Estimated total mortality for fish in the age range of 5-10 years is currently very high (three year average Z = 0.73), which is a large concern especially considering that reported landings have been only about half of the TACs over this time period. Short-term projections of the stock were not performed due to concerns related to variability in the survey data, the strong directional retrospective pattern in model estimates, and the unavailability of recent estimates of commercial fish weights-at-age. However, it is generally noted that biomass of the stock is likely to decline sharply in the coming years if the current high mortality rate persists.L'état du stock de morue dans la sous-division 3Ps de l’Organisation des pêches de l'Atlantique Nord-Ouest (OPANO) a fait l'objet d'une évaluation lors d'une réunion du processus régional d'examen par les pairs de Pêches et Océans Canada (MPO) qui s'est tenue du 17 au 19 octobre 2016 Les débarquements de l'année de gestion de 2015-2016 (du 1er avril au 31 mars) ont totalisé 6 427 tonnes, ce qui représente seulement 48 % du total autorisé des captures (TAC). Il s'agit de la sixième saison consécutive où le TAC n'est pas atteint. Au cours des dernières années, les estimations de l'abondance selon le relevé par navire de recherche mené au printemps par le MPO équivalaient à peu près aux moyennes, tandis que les estimations de la biomasse étaient généralement inférieures à la moyenne. Depuis 1999, les taux de prise des pêches sentinelles au filet maillant sont très faibles et stables. Depuis six ans, les taux de prise des pêches sentinelles à la palangre sont inférieurs à la moyenne. L'année 2015 est celle où le taux de prise a été le plus faible. Les estimations de la biomasse du stock reproducteur (BSR) calculées à partir d'un modèle de cohorte basé sur les relevés (SURBA) ont augmenté de façon importante au cours de la période 2009-2012, mais ont connu un déclin depuis. Bien que le stock se situe actuellement dans la zone de prudence (18 % au-dessus de la valeur Blim) définie par le cadre de l'approche de précaution du MPO, la probabilité que le stock tombe dans la zone critique est de 0,22, ce qui est préoccupant. D'autres préoccupations existent quant au fait que l'estimation actuelle de la BSR pourrait être biaisée, car le modèle a surestimé la BSR au cours des dernières années (c.-à-d., l'évaluation a fait l'objet de révisions rétrospectives à la baisse de la BSR). La BSR actuelle est très jeune et composée en grande partie (46 %) de poissons de 4 à 5 ans. Ces poissons sont tirés des fortes classes d'âge de 2011 et de 2012 qui n'ont pas encore atteint leur pleine maturité. La mortalité totale estimée des poissons âgés de 5 à 10 ans est actuellement très élevée (moyenne sur trois ans; Z = 0,73), ce qui constitue une grande préoccupation étant donné que les débarquements déclarés représentaient environ la moitié du TAC durant cette période. Les projections à court terme du stock n'ont pas été effectuées en raison de préoccupations liées à la variabilité dans les données d'enquête, de la forte tendance rétrospective directionnelle dans les estimations modélisées, et de la non-disponibilité de récentes estimations des poids selon l'âge des poissons commerciaux. Il convient toutefois de noter qu'en général, la biomasse du stock est susceptible de diminuer de façon marquée au cours des prochaines années si les taux de mortalité élevés actuels persistent