Size, structure, movement, and survival of American lobster, Homarus americanus, populations in areas with and without commercial harvesting

To determine the potential effectiveness of no-take reserves as a fisheries conservation tool for American lobsters (Homarus americanus), I quantified the size, structure, movement, and survival of lobsters inside and outside of two small no-take reserves (Round Island and Duck Islands) in Bonavista Bay, Newfoundland during 1997-1999. These no-take reserves were established by harvesters as part of a co-management plan for the local fishery and supported approximately 1.5% of the local lobster population. Although this study only concerned the first three years following reserve establishment, there were clear differences in lobster population parameters inside and outside of the no-take reserves. At the Round Island reserve, population density was high and stable over time, and female and male size increased, as did the proportion of ovigerous females. However, at the Duck Islands reserve, population density increased dramatically between 1997 and 1998, and male size increased over time, but there was no detectable change in female size or in the proportion of ovigerous females. Lobster density, female and male size, and the proportion of ovigerous females were greater within the Round Island reserve compared to an adjacent harvested area. At the Duck Islands, females and males were larger in size within the reserve but I found no difference in lobster density or the proportion of females that were ovigerous between the reserve and an adjacent harvested area. Differences in the response of some lobster population components to small no-take reserves can be explained by patterns of lobster movement and survival. Because the frequency of lobster emigration from the reserves was low (only 8.7% of tagged lobsters recaptured were in an area with a harvesting status different from that of where they were tagged) and harvesting pressure outside of the reserves was intense (annual harvesting mortality amounted up to 87.2% for lobsters eligible for commercial harvest), my results indicated that no-take reserves can offer increased survival to lobsters and may provide direct benefits to the local fishery

Northern Cod Comeback

The great “northern” cod (Gadus morhua) stock, formerly among the world’s largest and the icon for depletion and supposed non-recovery of marine fishes, is making a major comeback after nearly two decades of attrition and fishery moratorium. Using acoustic-trawl surveys of the main pre-spawning and spawning components of the stock, we show that biomass has increased from tens of tonnes to >200 thousand tonnes within the last decade. The increase was signalled by massive schooling behaviour in late winter first observed in 2008 in the southern range of the stock (Bonavista Corridor) after an absence for 15 years, perhaps spurred by immigration. Increases in size composition and fish condition and apparent declines in mortality followed, leading to growth rates approaching 30% per annum. In the spring of 2015, large increases in cod abundance and size composition were observed for the first time since the moratorium in the more northerly spawning groups of this stock complex. The cod rebound has paralleled increases in the abundance of capelin, Mallotus villosus, whose abundance declined rapidly in the cold early 1990s but has recently increased during a period of warm ocean temperatures. With continued growth in the capelin stock and frugal management (low fishing mortality), this stock could rebuild, perhaps within less than a decade, to historical levels of sustainable yield. More generally, if this stock can recover, the potential exists for recovery of many other depleted stocks worldwide.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Congruence of stock production and assessment areas? An historical perspective on Canada’s iconic Northern cod

Fisheries management requires spatially congruent production and assessment areas. Canada’s Northern cod, initially considered a stock complex distributed from northern Labrador to northern Grand Bank, had its northern boundary reduced to southern Labrador in the early 1970s. Spatial incongruence has resulted in spawning stock biomass (SSB) and recruitment (R) between historical and recent eras. To investigate temporal changes, four stanzas of SSB and R were derived from statistical Perron breaks. In stanza 1, the 1960s, spawning off northern Labrador coincided with higher SSB and R than in following stanzas from the 1970s onward. SSB-R relationships that include 1960s data do not represent potential production from a more southerly distributed stock. Loglinear models of R (density-dependent models did not improve fit) indicated SSB had greatest effect, and with indices of climate and south-north distribution explained 86% of variance. Lack of density-dependence suggests long-standing recruitment overfishing, making reference points problematic. SSB growth is suggested as an alternative management target. Rebuilding the Northern cod to historic abundance requires a full “portfolio” of spawning from northern Labrador to the Grand Bank (a re-managed 2+3KL stock). With a contracted range, lower production should be anticipated.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Evidence of near year-around spawning in Atlantic cod off southern Newfoundland: implications for management

Management of Atlantic cod (Gadus morhua) off southern Newfoundland (Northwest Atlantic Fisheries Organization (NAFO) Subdivision 3Ps) entails allocated quotas and restrictions on fishing during late winter and springtime to protect presumed spawning aggregations. We present data collected from research trawls and handlines (1995–2014) indicating spawning inshore may occur near year-around with limited resting from December to February and with more contracted spring spawning possible offshore. A mixed general linear model with binomial error, using year as a random factor, recognized month and length as significant impacts on proportions of females spawning, but not gear or inshore–offshore location. Composite data indicated that females in spawning condition may be present inshore (∼10%–20% of adult females) from March to October. During 1997–1999, with 8–9 months sampled each year, protracted annual spawning schedules and interannual variability were evident. At present, the fishery primarily employs gillnets inshore and otter trawls offshore, with spring spawning closures offering only partial and inconsistent protection. Behavioural interference might be reduced by employing less intrusive longlines, as historically practiced in this fishery.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Does redistribution or local growth underpin rebuilding of Canada's Northern cod?

The stock structure of Canadaâ s Northern cod, the largest of many depleted groundfish stocks having multiple spawning areas, is rebuilding by redistribution and not solely by local population growth. In 2007-2008, late winter acoustic surveys suggested initial rebuilding in the southern-most part of the offshore range (Bonavista Corridor, NAFO Divisions 3KL), likely including fish dispersing from the inshore. Thereafter, acoustically-determined biomass increases averaged 30% per annum (to near 240 000 t in 2014). In contrast, formerly dominant stock areas farther north retained few fish, mostly juveniles. In 2015, however, biomass in the northern stock range (NAFO Division 2J) reached 65 000 t and mid-north Notre Dame Channel (3K) reached 101 000 t, with Bonavista Corridor declining to 136 000 t. Biomass pooled over all surveyed regions totaled 302 000 t, consistent with sustained 30% growth. Latitudinal gradients in cod size, age distributions and individual growth existed both historically and recently, but not in 2015. The evidence suggests that the rapid increases of depopulated northern groups resulted from redistribution from the south within a metapopulation.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Otolith chemistry and redistributions of northern cod: evidence of Smith Sound-Bonavista Corridor connectivity

Stable oxygen isotope assays of otoliths (δThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Mating patterns and reversed size dimorphism in southern skuas (Stercorarius skua lonnbergi)

Numerous explanations exist for the evolution of reversed size dimorphism in raptorial species. A recent study concluded that reversed size dimorphism in skuas and jaegers was probably not attributable to breeding-role specialization, but that there was evidence for sexual selection, and in particular intrasexual competition by females for males. Our study tested the applicability of those conclusions for Southern (or Brown) Skuas (Stercorarius skua lonnbergi) breeding in South Georgia. Clutch volume was related positively to size and condition of females and negatively to condition of males, but there was no evidence of assortative mating for size or condition within pairs. Potential explanations for the discrepancy between this and previous studies are that size is less closely correlated with individual quality because of highly diverse foraging strategies, territory quality is a confounding factor, or because lower aggression in Southern Skuas reduces the necessity for small females to avoid large males

SNP_flanking_sequences and alleles_from_GadMor_May2010_alignment

SNP flanking sequences and alleles from GadMor_May2010_alignment (Star B, et al. Nature 2011 Aug 10)

Genetic variation in life-history reaction norms in a marine fish

Neither the scale of adaptive variation nor the genetic basis for differential population responses to the environment is known for broadcast-spawning marine fishes. Using a common-garden experimental protocol, we document how larval growth, survival and their norms of reaction differ genetically among four populations of Atlantic cod (Gadus morhua). These traits, and their plastic responses to food and temperature, differed across spatial scales at which microsatellite DNA failed to detect population structure. Divergent survival reaction norms indicate that warm-water populations are more sensitive to changes in food, whereas cold-water populations are more sensitive to changes in temperature. Our results suggest that neither the direction nor the magnitude of demographic responses to environmental change need be the same among populations. Adaptive phenotypic plasticity, previously undocumented in marine fishes, can significantly influence the probability of recovery and persistence of collapsed populations by affecting their ability to respond to natural and anthropogenic environmental change