Harvest Pressure on Coastal Atlantic Cod (Gadus morhua) from Recreational Fishing Relative to Commercial Fishing Assessed from Tag-Recovery Data
- Marine recreational fishing is a popular outdoor activity. However, knowledge about the magnitude of recreational catches relative to commercial catches in coastal fisheries is generally sparse. Coastal Atlantic cod (Gadus morhua) is a target species for recreational fishers in the North Atlantic. In Norway, recreational fishers are allowed to use a variety of traps and nets as well as long-line and rod and line when fishing for cod. From 2005 to 2013, 9729 cod (mean size: 40 cm, range: 15–93 cm) were tagged and released in coastal Skagerrak, southeast Norway. Both high-reward (NOK 500) and low-reward tags (NOK 50) were used in this study. Because some harvested fish (even those posting h…
Causes of mortality in depleted populations of Atlantic cod estimated from multi-event modelling of mark–recapture and recovery data
Knowledge on mortality causes is key for an effective management of animal populations and can help to restore depleted fish stocks. Here we investigated the mortality dynamics of coastal Atlantic cod (Gadus morhua) in Skagerrak, southern Norway, by analyzing local mark–recapture and recovery data collected from 2005 to 2013 (N = 9360 fish, mean length = 41 cm, range = 16–93 cm). By applying multi-event models to the data, we could link field observations to multiple “dead states” and estimate the proportion of deaths associated with different fishing gears while controlling for unobserved mortality and detection errors. Deaths due to hand lines and fixed gear types were dominant compared …
Lobster reserves as a management tool in coastal waters: Two decades of experience in Norway
9 pages, 4 figures.-- Under a Creative Commons license
Demographic responses to protection from harvesting in a long-lived marine species
Abstract Marine protected areas (MPAs) are usually considered to have positive effects on the recovery of over-exploited populations. However, resolving the extent to which MPAs function according to their conservation goals requires that essential demographic information such as individual survival and population size are quantified. To this end, we analyzed a 16-year replicated mark-recapture study on European lobster (Homarus gammarus, n = 8793) conducted at several protected and unprotected sites in southern Norway, quantifying the impact of MPAs on local population dynamics by means of a “before-after control-impact” study approach (BACI). Lobster survival and abundance were estimated …
Supplementary material for "Mesocarnivore community structuring in the presence of Africa's apex predator".
SI Appendix. Camera-trapping surveys and data summary; SII Appendix. Model formulation and parameter estimates of the multi-region community occupancy model; SIII Appendix. Multi-region community occupancy model JAGS code.
Coastal Research Seen Through an Early Career Lens—A Perspective on Barriers to Interdisciplinarity in Norway
The value of interdisciplinarity for solving complex coastal problems is widely recognized. Many early career researchers (ECRs) therefore actively seek this type of collaboration through choice or necessity, for professional development or project funding. However, establishing and conducting interdisciplinary research collaborations as an ECR has many challenges. Here, we identify these challenges through the lens of ECRs working in different disciplines on a common ecosystem, the Norwegian Skagerrak coast. The most densely populated coastline in Norway, the Skagerrak coast, is experiencing a multitude of anthropogenic stressors including fishing, aquaculture, eutrophication, climate chan…
Amphibian survival compromised by long-term effects of chytrid fungus
AbstractChytridiomycosis, the disease caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), has been unambiguously implicated in the decline of amphibian populations worldwide. However, the impact of this devastating infectious disease can be difficult to gauge without empirical data on the population-level effects of Bd. Often, assessments of the amphibian chytridiomycosis panzootic are based primarily on expert opinions; as a result, declines in tropical areas are promptly attributed to Bd while its impact on temperate species not suffering from adult mass mortalities is frequently overlooked. Here, we investigated the survival probability in an amphibian species from a tempe…
Protected areas buffer against harvest selection and rebuild phenotypic complexity
14 pages, 6 figures, 4 tables.-- This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited
Mesocarnivore community structuring in the presence of Africa's apex predator
This work was supported by the Peace Parks Foundation; G.C.S. was funded by a doctoral grant from Fundacão para a Ciência e a Tecnologia (FCT: PD/BD/114037/2015); L.H.S. was supported by the National Research Foundation, South Africa (UID: 107099 and 115040) and by the African Institute for Conservation Ecology. Apex predator reintroductions have proliferated across southern Africa, yet their ecological effects and proposed umbrella benefits of associated management lack empirical evaluations. Despite a rich theory on top-down ecosystem regulation via mesopredator suppression, a knowledge gap exists relating to the influence of lions (Panthera leo) over Africa's diverse mesocarnivore (less …
Restoration of Abundance and Dynamics of Coastal Fish and Lobster Within Northern Marine Protected Areas Across Two Decades
This article reviews a suite of studies conducted in a network of coastal Marine Protected Areas (MPAs) in Skagerrak, Southeast Norway. In 2006, Norway’s first lobster reserves were implemented, with the aim of protecting European lobster (Homarus gammarus) through a ban on fixed gear. A before–after control-impact paired series (BACIPS) monitoring program was initiated to evaluate effects of protection on depleted lobster populations. Experimental trapping and capture-recapture techniques were combined to track demography of populations, also including movement of individuals within and beyond MPAs and adjacent control areas. Further, population genetics and parentage studies were applied,…
Demographic effects of full vs. partial protection from harvesting: inference from an empirical before-after control-impact study on Atlantic cod
Summary In recent years, marine protected areas (MPAs) excluding all or some fishing activities have become widely applied as a tool to rebuild marine ecosystems and fisheries, but still, our knowledge of the effects of MPAs on the demography of harvested populations remains scarce, especially in cases where partly protected areas are still supporting some fishing activities. Here, we investigated the influence of partial protection – excluding fixed gears such as gillnets and traps but still allowing a hook and line fishery – on the demography of Atlantic cod Gadus morhua along the Norwegian Skagerrak coast. To do so, we applied novel multi-event models to a 9-year data set containing both…