Jon Helge Vølstad

Institute of Marine Research in Norway | IMR · Research Group of Fishery Dynamics

Recreational fishing (RF) is a large yet undervalued component of fisheries globally. While progress has been made in monitoring, assessing, and managing the sector in isolation, integration of RF into the management of multi‐sector fisheries has been limited, particularly relative to the commercial sector. This marginalises recreational fishers an...

Reliable information on the age- and size-structure of the annual harvest of major commercial fish stocks is crucial input to analytical stock assessments. Such information is usually obtained from landing data (census of biomass) combined with biological sampling of selected landings. In this paper we describe a novel catch sampling method that we...

Marine recreational fishing is popular in Norway, but current estimates of the catches by resident and tourist anglers are lacking due to several challenges, in particular Norway's long and intricate coastline with no defined access points and the large tourist fishery. To test methods for long-term monitoring of boat-based marine recreational angl...

Marine recreational fishing is popular in Norway, but current estimates of the catches by resident and tourist anglers are lacking due to several challenges, in particular Norway’s long and intricate coastline with no defined access points and the large tourist fishery. To test methods for long-term monitoring of boat-based marine recreational angl...

The hierarchical structure and non-probabilistic sampling in fisher self-sampling programmes makes it difficult to evaluate biases in total catch estimates. While so, it is possible to evaluate bias in the reported component of catches, which can then be used to infer likely bias in total catches. We assessed bias in the reported component of catch...

Since 1996, the European Union has required that fishery products of 35 fish species or groups of species, including crustaceans and cephalopods, be graded before being landed on the basis of commercial size-categories. A multi-stage sampling scheme to estimate catch-at-length and catch-at-age compositions of total annual landings has been conducte...

The REDUS project (2016-2020) has been a strategic project at the Institute of Marine Research (IMR) aimed at quantifying and reducing the uncertainty in data-rich and age-structured stock assessments (e.g., cod, herring, haddock, capelin). Work was organized in four topical work-packages: Fisheries-dependent (catch) surveys and assessment modeling...

Smartphone applications (apps) that target recreational fishers are growing in abundance. These apps have the potential to provide data useful for management of recreational fisheries. We surveyed expert opinion in 20, mostly European, countries to assess the current and future status of app use in marine recreational fisheries. The survey revealed...

Harbour porpoise (Phocoena phocoena) bycatch for Norwegian commercial gillnet fisheries from 2006 to 2018 was estimated using a traditional ratio estimator and generalized additive linear mixed models, with weight of fish landed and number of gillnet hauls as proxies for fishing effort. Estimates were derived from data collected with a contracted r...

Objective: The aim of the study was to evaluate the efficiency and consistency in the collection of ground reaction forces using one or two force plates from dogs with stifle lameness. Animals: Twenty-two client-owned dogs with unilateral stifle lameness were used. Methods: In a prospective study design, data were collected at a single time po...

The North Sea cod stock assessment is based on indices of abundance-at-age from fishery-independent bottom trawl surveys. The age structure of the catch is estimated by sampling fish for otoliths collection in a length-stratified manner from trawl hauls. Since age determination of fish is costly and time consuming, only a fraction of fish is sample...

Norwegian report on methods to estimate the Norwegian fishery for European lobster (Homarus gammarus) based on a license system

This report summarises the national contributions in 2018–2019 and the planning for the 2019–2020 surveys coordinated by the International Bottom Trawl Survey Working Group (IBTSWG). In the North Sea, the surveys are performed in quarters (Q) Q1 and Q3 while in the Northeast Atlantic the surveys are conducted in Q1, Q3, and Q4 with a suite of 14 na...

Norway has the highest participation rate in marine recreational fisheries (MRF) in Europe, and is popular among marine tourist anglers. Fishing licences are not required for marine recreational anglers, and the complex and long coastline makes on-site surveys a challenge. A novel approach for spatial sampling was developed and tested in on-site su...

The general decline of seabird populations worldwide raises large concerns. Although multiple factors are interacting to cause the observed trends, increased mortality from incidental bycatch in fisheries has proven to be important for many species. However, the bulk of published knowledge is derived from longline fisheries, whereas bycatch in gill...

Formulas for the mean stratified estimator and the GLMM used in the analysis. The mean stratified estimator is an estimator of bycatch per trip across all vessels. The GLMM was parameterised for both diving seabirds and surface feeding seabirds. (DOCX)

Marine recreational fishing (MRF) is a high-participation activity with large economic value and social benefits globally, and it impacts on some fish stocks. Although reporting MRF catches is a European Union legislative requirement, estimates are only available for some countries. Here, data on numbers of fishers, participation rates, days fished...

The Northeast Atlantic (NEA) mackerel (Scomber scombrus) is a widely distributed pelagic fish species that plays a key role in the marine ecosystem. In recent years, there has been a large fishery targeting mackerel in the NEA. At the same time as the geographic range of the mackerel fishery has expanded and the spatial distribution of the stock be...

The abundance and biomass of the Norwegian spring-spawning herring (NSSH) stock are assessed annually using a virtual population analysis (VPA) applied to catch-at-age data from the fishery and fishery-independent abundance indices derived from research vessel surveys for calibration (‘tuning’). The most important of these surveys is the Internatio...

Multi-annual management plans are important tactical arrangements to support upper-level marine resource policies in many countries. The newly reformed Common Fisheries Policy in the EU reiterates the role of management plans, supported by the development of harvest algorithms, commonly called harvest control rules (HCRs). Current HCRs for most com...

With diminishing seabird populations and little knowledge on incidental bycatch in fisheries in the Northeast Atlantic, this study aimed to screen seabird bycatch in Norwegian coastal fisheries in 2009. The purpose was to 1) quantify magnitude of seabird bycatch rates and estimate total bycatch from the entire fleet by different estimators 2) evalu...

At both state and local levels, bioassessment programs supply valuable information to guide stream resource management. For example, a regulatory decision-making framework is currently being developed by the Maryland Department of the Environment (MDE) for listing watersheds (Maryland 8-digit and 12-digit watersheds) as impaired based on indices of...

This manuscript describes a demographic model for the Eastern oyster (Crassostrea virginica) in the Chesapeake Bay that was developed using existing data from many researchers and sources. The authors developed the model structure, parameterized most of the input variables, and implemented the model in the Java™ programming language; however, the m...

Effective management of multi-species fisheries requires reliable estimates of the amount and composition of catch and bycatch. In this report, we present the results of analyses of observer program data performed to compare several different estimators of catch and catch composition. Our analyses were applied to 1994 data collected in two fisherie...

This report to the Chesapeake Bay Stock Assessment Committee details the results of research conducted by the University of Maryland Center for Environmental and Estuarine Studies (UMCEES) between 1October 1992 and 30 September 1993. The winter dredge survey was conducted from January 7 through March 27 by UMCEES and the Maryland Department of Natu...

This report summarizes key findings and recommendations of the Vessel Selection Bias Workshop held in Woods Hole, MA, from May 17-19, 2006. The report identifies procedures employed in observer programs to select vessels for observation and other factors that could cause bias in estimates of catch and bycatch, and provides recommendations for impro...

Technical report to U.S. Environmental Protection Agency Research Triangle Park, NC, on survey sampling methods.

Atlantic cod (Gadus morhua) caught in recreational fisheries are commonly released, often with barotrauma after rapid decompression. Mouth-hooked, non-bleeding cod kept in a floating net pen showed mortalities ≥40% when angled from >50 m depth, likely because of cumulative stress from ongoing barotrauma and exposure to warm surface water. In a natu...

Estimates of age compositions of fish populations or catches that are fundamental inputs to analytical stock assessment models are generally obtained from sample surveys, and multistage cluster sampling of fish is the norm. We use simulations and extensive empirical survey data for Northeast Arctic cod (Gadus morhua) to compare the efficiency of es...

The Workshop on Sampling Design and Optimization (WKSDO), chaired by Cristina Silva and Manuela Azevedo (IPMA-PT) and Jon H. Vølstad (IMR-NO) met in Lisbon, 17–20 November 2014, to focus on the analysis of the current Portuguese sampling designs under PNAB/DCF (Programa Nacional de Amostragem Biológica/Data Collection Framework) with the aim to opt...

Artisanal fisheries are often overlooked by fisheries management agencies despite their great importance for food security and livelihoods. The assessment and management of those fisheries is often rare, especially in developing countries. In Mozambique, a probability-based survey for the monitoring of the small-scale fisheries has been conducted i...

Catch and effort data form an important, and often the only, source of data for stock assessment and management of marine resources in developing countries. Population parameters and management quantities important for stock assessment are often estimated by fitting production models to standardized series of catch-per-unit-effort (CPUE). Such basi...

A demographic model was developed for oyster populations in the Chesapeake Bay, USA, to explore population responses to proposed management actions in support of an Environmental Impact Statement and Environmental Risk Assessment for oyster restoration. The model indicated that high natural mortality due to disease strongly controlled the populatio...

While catch-and-release (C&R) is a well-known practice in several European freshwater recreational fisheries, studies on the magnitude and impact of this practice in European marine recreational fisheries are limited. To provide an overview of the practice and magnitude of C&R among marine recreational anglers in Europe, the existing knowledge of C...

he role of recreational fisheries in the competition for marine resources is increasingly recognised. Their contribution in stock dynamics needs to be accounted for in assessments and management. Management regulations should be based on scientific advice on human and biological dimensions to be effective in reaching their goals. A survey among mar...

The demand for scientific knowledge in coastal zone governance is increasing, and multi-disciplinary science is now a requirement for most policy initiatives. Coastal zone management is highly complex, as many of the governance objects, drivers and effects are transitory and dynamic. In addition, coastal governance is usually conducted within a com...

A Bayesian hierarchical model was developed to estimate catch-at-age from commercial fishery data. Most common forms of data can be utilized: age and length, length-stratified ages, and length only. There is no need to construct an age-length key. Both landings and discards can be estimated, as can the effects of age reading errors. Estimates can b...

The rules for setting quotas for NorthEast Arctic cod (NEAc) are based on how estimates of stock parameters relate to defined biological reference points obtained from the Extended Survivors Analysis (XSA) model, calibrated using bottom trawl survey data from the Barents Sea. In this paper we use simulations to investigate how the precision in esti...

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 survey...

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Recreational fishing 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...

Recreational angling has become an increasingly important part of the Norwegian tourism industry and may contribute significantly to the fishing mortality of the Norwegian coastal cod (Gadus morhua) stock, which might presently be overfished. A national probability-based survey was conducted during 2009 to estimate the harvest of cod and eight othe...

Recreational fishing has become an important part of the Norwegian tourist industry. The coastal municipality of Risør, southern Norway, is considering further development of its marine fishing tourism to increase local economic benefits, but they also want to limit negative effects on the local ecosystem and for the inhabitants. We developed an in...

Vølstad, J. H., Korsbrekke, K., Nedreaas, K. H., Nilsen, M., Nilsson, G. N., Pennington, M., Subbey, S., and Wienerroither, R. 2011. Probability-based surveying using self-sampling to estimate catch and effort in Norway's coastal tourist fishery. – ICES Journal of Marine Science, 68: 1785–1791. Recreational fishing as a tourist activity has become...

To meet the requirements of the Clean Water Act, the States of Maryland and Virginia are using benthic biological criteria for identifying impaired waters in Chesapeake Bay and reporting their overall condition. The Chesapeake Bay benthic index of biotic integrity (B-IBI) is the basis for these biological criteria. Working together with the states...

Federal and state environmental agencies conduct several programs to characterize the environmental condition of Chesapeake Bay. These programs use different benthic indices and survey designs, and have produced assessments that differ in the estimate of the extent of benthic community degradation in Chesapeake Bay. Provided that the survey designs...

The Clean Water Act presents a daunting task for states by requiring them to assess and restore all their waters. Traditional monitoring has led to two beliefs: (1) ad hoc sampling (i.e., non-random) is adequate if enough sites are sampled and (2) more intensive sampling (e.g., collecting more organisms) at each site is always better. We analyzed t...

In an effort to restore the ecological role of oysters in Chesapeake Bay and the economic benefits of a commercial fishery, the states of Maryland and Virginia are considering introducing the nonnative Asian oyster (Crassostrea ariakensis) into the Bay. As part of an ecological risk assessment (ERA) to evaluate the proposed action and alternatives,...

Identifying the habitat requirements of marine fish is necessary to conserve and manage their populations, but these requirements are poorly understood for many species. One method of screening for important habitat characteristics is to identify differences in habitat features between areas of high and low fish abundance. We tested the association...

We used probability-based aerial−access surveys to estimate effort, catch, and harvest of American shad Alosa sapidissima and striped bass Morone saxatilis by recreational anglers in the Delaware River and upper estuary in 2002. Sampling of anglers at access points and flights over the river were conducted weekly from mid-March through October. Dai...

The integration of biological indicator results from the probabilistic monitoring designs of three neighboring states serves as a demonstration for what could be achieved nationwide under future implementation of the State-EPA Wadeable Streams Assessment. The U.S. Environmental Protection Agency (U.S. EPA) has developed methods for an estimate of s...

Biological indicators are critical to the protection of small, headwater streams and the ecological values they provide. Maryland and other state monitoring programs have determined that fish indicators are ineffective in small streams, where stream salamanders may replace fish as top predators. Because of their life history, physiology, abundance,...

In Maryland. U.S., an interim framework has recently been developed for using biologically based thresholds, or 'biocriteria', to assess the health of nontidal streams statewide at watershed scales. The evaluation of impairment is based on indices of biological integrity from the Maryland Biological Stream Survey (MBSS). We applied logistic regress...

Freshwater biological monitoring and assessment programs using biological indicators of ecological integrity (biocriteria) are integral to successful water resources planning and decision making. In the United States, the Clean Water Act requires every state to evaluate whether or not the designated aquatic life use (defined in its water quality st...

We estimated absolute abundance of the blue crab stock in Chesapeake Bay during winter from stratified random surveys conducted baywide from 1990 to 1999, using the swept-area method. We estimated catching efficiency of the survey gear from multiple depletion experiments to correct for temporal and vessel/area differences in catchability. The surve...

The Chesapeake Bay benthic index of biotic integrity (B-IBI) was developed to assess benthic community health and environmental quality in Chesapeake Bay. The B-IBI provides Chesapeake Bay monitoring programs with a uniform tool with which to characterize bay-wide benthic community condition and assess the health of the Bay. A probability-based des...

A winter dredge survey of blue crab (Callinectes sapidus Rathbun) is conducted annually in Chesapeake Bay as a key element of a long-term, bay-wide population dynamics study. Removal experiments are performed routinely as part of this stratified random survey of the blue crab population. We present a method for estimating the catching efficiency of...

This study examines the effect of survey design on the precision of estimates of average weight of stomach contents of fish. Since prey distribution is often patchy, fish at a station tend to have more similar stomach contents than do fish from different stations. Theory for evaluating the effects of intra-cluster correlation and variable density o...

In a previous paper (Pennington and Volstad, 1991, Biometrics 47, 717-723), it was suggested that reducing the size of the sampling unit currently used in marine surveys could increase the precision of the resulting density estimates. But if unit size is reduced, fewer animals will be caught during a survey. Concern has been expressed that this red...

Data from several trawling experiments and from some scallop dredge surveys indicate that, within limits, a smaller sampling unit can be more efficient than a larger unit for marine abundance surveys. Taking into account survey costs and sampling variability, the unit size is found that produces the most precise density estimate given a fixed amoun...

The standard tow duration for trawl surveys is normally from 30 min to 2 h. In this paper we investigate if catch rates for different size groups change for varying durations of from 5 min to 2 h. Data for cod, haddock and long rough dab from the Barents Sea and Georges Bank are analyzed. Owing to small fish-large fish differences in swimming capac...

Annual variations in freshwater flow and wind may influence the dispersal of oyster larvae (by affecting circulation patterns) and the survival of adults (by influencing salinity-dependent disease mortality) in Chesapeake Bay, a region whose oyster fishery has greatly declined. These observations suggest that environmental variability has important...

In Chesapeake Bay, the blue crab (Callinectes sapidus) fishery uses traps as the primary gear for harvest. Conservative estimates suggest that up to 500,000 crab traps are fished daily during peak season. There are no current estimates of trap losses, but undoubtedly a percentage of traps are lost annually. Lost traps can continue to capture and ki...

BACKGROUND The Chesapeake 2000 (C2K) Agreement commits regional jurisdictions to implement multispecies approaches to fisheries management. The potential for biological interactions and technical interactions within traditional single species management has motivated the development of multispecies approaches. Houde et al. (1998)1 reported the reco...