Alf Ring Kleiven

Lobster and cod benefit from small-scale northern marine protected areas: inference from an empirical before–after control-impact study

Marine protected areas (MPAs) are increasingly implemented as tools to conserve and manage fisheries and target species. Because there are opportunity costs to conservation, there is a need for science-based assessment of MPAs. Here, we present one of the northernmost documentations of MPA effects to date, demonstrated by a replicated before–after control-impact (BACI) approach. In 2006, MPAs were implemented along the Norwegian Skagerrak coast offering complete protection to shellfish and partial protection to fish. By 2010, European lobster (Homarus gammarus) catch-per-unit-effort (CPUE) had increased by 245 per cent in MPAs, whereas CPUE in control areas had increased by 87 per cent. Mean size of lobsters increased by 13 per cent in MPAs, whereas increase in control areas was negligible. Furthermore, MPA-responses and population development in control areas varied significantly among regions. This illustrates the importance of a replicated BACI design for reaching robust conclusions and management decisions. Partial protection of Atlantic cod (Gadus morhua) was followed by an increase in population density and body size compared with control areas. By 2010, MPA cod were on average 5 cm longer than in any of the control areas. MPAs can be useful management tools in rebuilding and conserving portions of depleted lobster populations in northern temperate waters, and even for a mobile temperate fish species such as the Atlantic cod.

Total catch of a red-listed marine species is an order of magnitude higher than official data.

Accurate information on total catch and effort is essential for successful fisheries management. Officially reported landings, however, may be underestimates of total catch in many fisheries. We investigated the fishery for the nationally red-listed European lobster (Homarus gammarus) in south-eastern Norway. Probability-based strip transect surveys were used to count buoys in the study area in combination with catch per unit effort data obtained independently from volunteer catch diaries, phone interviews, and questionnaires. We estimate that recreational catch accounts for 65% of total catch in the study area. Moreover, our results indicate that only a small proportion (24%) of lobsters landed commercially were sold through the legal market and documented. Total estimated lobster catch was nearly 14 times higher than reported officially. Our study highlights the need for adequate catch monitoring and data collection efforts in coastal areas, presents a clear warning to resource managers that illegal, unreported and unregulated (IUU) fisheries in coastal areas should not be ignored, and shows the potential impact of recreational fisheries.

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 high-reward tags) may go unreported by fishers, reporting rates were estimated from mark-recovery models that incorporate detection parameters in their structure, in addition to survival and mortality estimates. During 2005 to 2013, a total of 1707 tagged cod were recovered and reported by fishers. We estimate the overall annual survival to be 33% (SE 1.5). Recreational rod and line fishing were responsible for 33.7% (SE 2.4) of total mortality, followed by commercial fisheries (15.1% SE 0.8) and recreational fixed gear (6.8% SE 0.4). Natural mortality was 44.4% (SE 2.5) of total mortality. Our findings suggest that recreational fishing—rod and line fishing in particular—is responsible for a substantial part of fishing mortality exerted on coastal cod in southern Norway.

Estimating Recreational and Commercial Fishing Effort for European Lobster Homarus gammarus by Strip Transect Sampling

Abstract Recreational fishing effort for coastal marine species can be significant but is often challenging to estimate. Here we present a case study where a probability-based strip transect survey is used to estimate effort in the Norwegian fishery for European lobster Homarus gammarus. This fishery is conducted by both recreational and commercial fishers, but reliable information on total fishing effort and total catch is lacking. In 2008, we conducted a strip transect sampling survey throughout the lobster fishing season in southern Norway to estimate the number of deployed lobster traps over time. Surface buoys marking lobster traps were counted along strip transects placed representatively in the survey area in five different weeks throughout the lobstering season. Calibration studies were conducted to standardize transect width and to estimate and adjust for detection rates of buoys along transect strips. Mean number of lobster traps per square kilometer and associated variance was estimated by a ratio estimator using bootstrapping, with transects as the primary sampling units. Poststratification of the counts by depth (by 10-m depth intervals) combined with geographical information systems mapping improved the precision of the estimated density of lobster traps and increased the effective sample size of transects by 22–44% per week. Estimated daily effort for the first week was 48.95 (SE = 3.11) traps/km2, decreasing steadily to 5.96 (SE = 0.79) in the eighth (and last) week of the lobster season. Our study shows that lobster traps deployed by recreational fishers outnumber the ones deployed by commercial fishers, contributing to 65 % of the total effort (number of traps) in the fishery. We show that strip transects are a suitable way to estimate effort in the Norwegian lobster fishery. We conclude that improved management efforts need to target recreational as well as commercial fishing activities in order to achieve effective management of the red-listed species.

Who is fishing on what stock: population-of-origin of individual cod (Gadus morhua) in commercial and recreational fisheries

Who is fishing on what stock: population-of-origin of individual cod (Gadus morhua) in commercial and recreational fisheries Per Erik Jorde, Alf Ring Kleiven*, Marte Sodeland, Esben Moland Olsen, Keno Ferter, Sissel Jentoft, and Halvor Knutsen Institute of Marine Research, Nye Flødevigveien 20, N-4817 His, Norway Department of Biosciences, Centre for Ecological and Evolutionary Synthesis, University of Oslo, PO Box 1066, Blindern, N-0316 Oslo, Norway Centre of Coastal Research, University of Agder, PO Box 422, N-4604 Kristiansand, Norway Institute of Marine Research, PO Box 1870, N-5817 Bergen, Norway *Corresponding author: tel: þ47 93871639; e-mail: ark@hi.no.