Frameless-Finding and Refining A Sampling Frame for Surveying Recreational Fisheries: Lessons from Estimating Swedish Harvest of Western Baltic Cod

To achieve sustainable fisheries, advice to management should be based on reliable science and unbiased data. Attaining quality data (i.e. precise and unbiased) on recreational fishing can be challenging, particularly when prior knowledge of the sector is limited and a proper sample frame of recreational fishers or vessels does not exist. In this study, a registry of access points was constructed for the Swedish south–west coast and used as a spatial sample frame in determining both effort and catches of the private boat fishery. Sampling dates, times for sampling, and access points visited were selected using probabilistic methods, ensuring unbiased results. The final multi-stage sampling design involved multiple strata, clusters, and probability selection methods and enabled first-time estimation of Swedish recreational landings of western Baltic cod by private boats to be used in stock assessment. Concurrent data collection covering aspects such as boat counts at access points, provided additional information on e.g. activity patterns. That additional information opens possibilities to refine the design of the original survey and optimize the sampling effort towards different goals, such as other fished resources. In this paper, we reflect on the challenges that limitations in initial information poses to the design and deployment of a new recreational fisheries survey. We suggest ways, whereby indirect sampling frames can be developed from initially incomplete or limited information to access the fishers and their catch. Our experience shows that, despite initial frame and knowledge limitations, full probabilistic methods are worth considering in data limited scenarios and that the design-based point estimates and variances they provide on recreational fishing effort and catches are useful in guiding initial management and the next steps of survey improvement

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Recreational fisheries – characterization, quantification and biological impact on natural resources

Recreational fishing is of high social and economic value worldwide, and participation is increasing at a global scale. The extent and biological effect of recreational fisheries have only recently been characterized on a limited number of targeted stocks in Europe. Several studies have shown that there is an effect of recreational fisheries on stock status in Europe and globally, and the importance of acknowledging this sector is increasingly conceded. In Sweden, recreational fishing is defined by the Swedish Agency for Marine and Water Management as any fishing without a professional licence, i.e. fishing for own consumption, recreation, tourism and for competition. Annual surveys have shown that at least 1.4 million Swedes participate in recreational fisheries at least once per year, and total catches have been estimated to about 18 380 t. The species most frequently caught in Swedish recreational fisheries are perch, pike, brown trout, crayfish, lobster, Zander, salmon, Atlantic mackerel, Atlantic herring, and cod. Recreational fisheries are covered in national as well as international management strategies for sustainable fisheries, in particular the common fisheries policy (CFP). The CFP concerns adopting a precautionary approach to fisheries management, and in support of this the EU Data Collection Framework was introduced in 2001. In accordance with this, member states are obliged to collect data on e.g. recreational fisheries for selected species defined under the DCF (EU, 2008) or EU-MAP (EU, 2016). The current knowledge on recreational fisheries in Sweden is largely based on combined postal surveys and follow-up by telephone conducted by Statistics Sweden (SCB) on behalf of HaV. In this essay, the current knowledge on the Swedish recreational fisheries, available methods and key species is reviewed. Important research topics needing further examination, aiding the fulfilling the data collection obligations and increasing the overall understanding and knowledge of the Swedish recreational fisheries, are stated

Temperature and age effects on latitudinal growth dynamics of the commercially valuable gadoid Northeast Arctic saithe (Pollachius virens)

It is well known that marine fish dynamics relate with climate variability, and predicting future population developments have become increasingly urgent with on-going climate change. One approach in widespread populations is to study how individuals from different parts of the distribution area respond to climate, thereby testing for potential resilience in terms of local adaptions against environmental change. In this study, we collated extensive survey data on size-at-age for Northeast Arctic saithe (Pollachius virens) (1992–2013; 62–70 °N; ages 0–3 years) and detailed hydrographic information from three fixed, coastal stations along the Norwegian coast (at ≈63, 68 and 71 °N). Dedicated ad libitum feeding experiments were additionally performed to further strengthen the insight in saithe growth dynamics, also including adults (≥4 years). Likely temperature-mediated effects on whole body weight (W), total length, Fulton's K, and specific growth rate (SGR) of wild saithe were explored using generalized linear models with age and region as fixed factors. A positive relationship with temperature was found, as evidenced by the before-mentioned body metrics of saithe age 2–3 years all becoming higher at positive local annual temperature anomalies, i.e. the deviation from the long-term mean temperature. The direct use of corresponding, absolute temperature instead of temperature anomalies gave comparable results. Hence, acclimatization to local temperatures per se was likely minor. Furthermore, examination of GLM interaction terms indicated that dissimilar feeding conditions in part of the study area, using K as a proxy, were not a confounding factor. Taken together, the present material provided an excellent opportunity to scrutinize temperature-mediated effects on growth dynamics across age classes, regions, and years. However, data sets pooled over years turned out to be more informative: SGR from age 0 to 1 year was clearly highest in the warmer, southern region but individuals in the colder, northern region gradually caught up and thereby showed higher W at age 3 years. This pattern mechanistically speaks for a gradual displacement of response curves for growth towards lower temperatures as saithe become larger or older. Although the present feeding experiments evidenced steady declines in SGR with W for younger individuals while this size effect faded away in the adults, the results also implied that saithe in the field show far from optimal growth performance, according to standard physiological principles. Thus, the term “optimal growth” should be treated with caution. Nevertheless, further studies are merited in this research area, potentially aiding body growth predictions and thereby management routines of this productive stock

Expert opinion on using angler Smartphone apps to inform marine fisheries management: status, prospects, and needs

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 that a few countries already use app data to support existing data collection, and that this number is likely to increase within 5–10 years. The strongest barriers to use app data were a scarcity of useful apps and concern over data quality, especially biases due to the opt-in nature of app use. Experts generally agreed that apps were unlikely to be a “stand-alone” method, at least in the short term, but could be of immediate use as a novel approach to collect supporting data such as, fisheries-specific temporal and spatial distributions of fishing effort, and aspects of fisher behaviour. This survey highlighted the growing interest in app data among researchers and managers, but also the need for government agencies and other managers/researchers to coordinate their efforts with the support of survey statisticians to develop and assess apps in ways that will ensure standardisation, data quality, and utility