Using the best of two worlds: A bio-economic stock assessment (BESA) method using catch and price data

Reliable stock assessments are essential for successful and sustainable fisheries management. Advanced stock assessment methods are expensive, as they require age- or length-structured catch and detailed fishery-independent data, which prevents their widespread use, especially in developing regions. Furthermore, modern fisheries management increasingly includes socio-economic considerations. Integrated ecological-economic advice can be provided by bio-economic models, but this requires the estimation of economic parameters. To improve accuracy of data-limited stock assessment while jointly estimating biological and economic parameters, we propose to use price data, in addition to catches, in a new bio-economic stock assessment (‘BESA’) approach for de-facto open access stocks. Price data are widely available, also in the Global South. BESA is based on a state-space approach and uncovers biomass dynamics by use of the extended Kalman filter in combination with Bayesian estimation. We show that estimates for biological and economic parameters can be obtained jointly, with reliability gains for the stock assessment from the additional information inherent in price data, compared to alternative assessment methods for data-poor stocks. In a real-world application to Barents Sea shrimp (Pandalus borealis, Pandalidae), we show that BESA benchmarks well also against advanced stock assessment results. BESA can thus be both a stand-alone approach for currently unassessed stocks as well as a complement to other available methods by providing bio-economic information for advanced fisheries management.publishedVersio

The Spawners' Shadow price: Joint Production of Recruitment and Growth in Agestructured Fish Populations

Fishery scientists distinguish between recruitment overfishing (i.e. suboptimally low reproduction because the spawning stock is fished down) and growth overfishing (i.e. catching fish at an inefficiently young age). We use an age-structured bio-economic model to study how important the (endogenous) recruitment is compared to the growth of individual fish under optimal management of the fishery, and how severe the problem of recruitment overfishing is at different stock sizes. We answer both questions by quantifying the spawners' shadow price, i.e. the shadow price of the spawning stock under optimal management. We find that the spawner's shadow price may even be negative in optimal steady state. This surprising result arises because recruitment and growth are joint products in age-structured fish populations. Our quantitative analysis for the Eastern Baltic cod fishery shows, however, that the problem of recruitment overfishing does cause large economic costs, as the shadow price of the spawning stock biomass has reached levels between one and two Euros per kilogram in the 1990s and early 2000s, which is a large figure, compared to average landing prices for Eastern Baltic cod of about two Euros per kilogram

Chapter 8 Stakeholders' normative notions of sustainability

Chapter 8 = Many fisheries world-wide are not operating sustainably. Returning to sustainable levels is challenging as fisheries are embedded in complex marine social-ecological systems and bringing the system back to a path of sustainability will likely involve conflicts and tough choices. A first step towards a path of sustainability relates to understanding the (different) normative notions of sustainability held by different stakeholder groups. We use the (German) Western Baltic Sea as a case study to elicit these normative views. At a workshop with representatives of relevant stakeholder groups, we conducted a questionnaire-based survey. Questions were inspired by the stochastic-viability-conceptualization of strong ecological-economic sustainability under uncertainty. The survey focused on sustainability as a normative goal for fisheries management from a societal perspective. It returns quantitative results which can be directly utilized in fisheries management. We find considerable variation across as well as within stakeholder groups in their normative views on sustainability. Still, it seems to be consensus among all stakeholders that the different groups have legitimate claims to the Western Baltic Sea, providing common ground on how to 28 sustainably use the WBS, and a well-designed transdisciplinary approach with broad exchange between different stakeholders and science seems useful to steer the WBS into a sustainable future

Chapter 1 The multifaceted picture of transdisciplinarity in marine research

Chapter 1 = The Swiss psychologist Jean Piaget is considered responsible for coining the term transdisciplinarity’ in the 1970s, defining it as a higher stage after the interdisciplinary relations. To date, transdisciplinarity research is a growing field in academia, but still there is no uniform definition. In this book chapter, we explore how the term ‘transdisciplinarity’ is used in marine research including different fields like quantitative ecology and modeling, marine social science or marine conservation. We used a quantitative full-text analysis of peer-reviewed journal publications from 1992 to 2021, ensuring to include most recent contributions to the analysis. A total of over 6000 publications could be identified, about 500 of these focusing on marine realm. We applied an agglomerative hierarchical cluster analysis (program R) to consider relative frequencies of significant conceptual words within the transdisciplinary landscape. Multiple research clusters have been identified and further divided regarding the study background (e.g., meta-analysis, case study, theory)

To tip or not to tip: The Window of Tipping Point Analysis for social‐ecological systems

We introduce six steps to define a “Window of Tipping Point Analysis” which serves as a framework to increase the understanding of processes and tipping points in social-ecological systems. We apply the Window of Tipping Point Analysis to a mathematical model and two case studies (i.e., Baltic Sea and the Humboldt Current Upwelling system), focusing on three aspects. In “to tip or be tipped” we look at agency in preventing (or driving) tipping. In “to be tipped or not to be tipped” we discuss intertemporal developments and chosen time periods for delineating regime shifts. In “to tip or not to tip” we discuss the desirability of states and their relation to the elements included. We argue that agency in tipping-point management, the occurrence of tipping points, and desirable states depend on the window chosen for the analysis

Ocean warming and acidification may drag down the commercial Arctic cod fishery by 2100

The Arctic Ocean is an early warning system for indicators and effects of climate change. We use a novel combination of experimental and time-series data on effects of ocean warming and acidification on the commercially important Northeast Arctic cod (Gadus morhua) to incorporate these physiological processes into the recruitment model of the fish population. By running an ecological-economic optimization model, we investigate how the interaction of ocean warming, acidification and fishing pressure affects the sustainability of the fishery in terms of ecological, economic, social and consumer-related indicators, ranging from present day conditions up to future climate change scenarios. We find that near-term climate change will benefit the fishery, but under likely future warming and acidification this large fishery is at risk of collapse by the end of the century, even with the best adaptation effort in terms of reduced fishing pressure.publishedVersio

Political overfishing: Social-economic drivers in TAC setting decisions

Sustainable use of marine resources, as targeted by Ecosystem-Based Fishery Management (EBFM), is a highly ranked policy goal. However, many marine fish stocks are still overused, challenging sustainability goals. Reasons for this policy failure are disputed and they might be manifold, including economic, institutional, and social drivers. We use Generalized Additive Models (GAMs) to empirically determine and quantify the importance of interacting ecological, economic, and social drivers in a political decision making process, i.e. the setting of annual Total Allowable Catch (TAC) limits. GAMs allow non linear relationships between response and explanatory variables and due to their flexibility have successfully been applied to investigate ecosystem dynamics. Here, we use this modeling approach in a novel way to quantify social-economic-ecological feed-backs on policy decisions. European fisheries policy agreed in most cases to TACs higher than scientifically advised. We recorded this deviation for all managed European fish stocks for the time-series 1987-2013. Additionally, we make use of available time-series of socio-economic and ecological variables potentially influencing the decision, including national unemployment rates, stock status, economic growth rates, and employment in fisheries. We show that political decisions on TACs are not only driven by scientific advice on the ecological state of the stock, but that socio-economic variables have a significant effect on TACs – however not related to sound scientific advice. We conclude that scientific advice for a successful implementation of EBFM will have to address socio-economic driving forces more explicitly

Assessing Social - Ecological Trade-Offs to Advance Ecosystem-Based Fisheries Management

Peer reviewe

ecoOcean - games in Fisheries education, communication and science

There is growing realization of the potential for games and experiments as powerful tools for education, outreach and research in many fields of science. Particularly in fisheries management we face a growing demand for stakeholder involvement, which requires new ways in reaching informed decision making. Games and experiments can be used for (i) teaching economic and ecological principles to pupils, students and the general public, (ii) outreach and communication with stakeholders in participatory assessment or management environments, and (iii) collecting scientific data in controlled research experiments. We developed a conceptual approach and realized the fisheries simulation game ecoOcean. This tool has so far primarily been used for dissemination purposes. The great success of the current version of the game is a strong motivation to proceed on these lines. The game shall be further developed to include a higher complexity and enable the simulation of management measures, i.e. the stakeholder can play through management measures. The paper shall rise awareness of the strengths of this new approach to stakeholder involvement. We will describe past and current approaches and draw a vision on future use of games in education, communication and science, using the conceptual approach we have taken with ecoOcean