Ecosystem-based fishery management (EBFM) is a new direction for fishery management, essentially reversing the order of management priorities so that management starts with the ecosystem rather than a target species. EBFM aims to sustain healthy marine ecosystems and the fisheries they support.
 Pikitch
 et al .
 describe the potential benefits of implementation of EBFM that, in their view, far outweigh the difficulties of making the transition from a management system based on maximizing individual species.

https://science.sciencemag.org/content/sci/305/5682/346.full.pdf

Ecosystem-Based Fishery Management

Climate influences a population through a variety of processes, including reproduction, growth, migration patterns and phenology. Climate may operate either directly through metabolic and reproductive processes or indirectly through prey, predators, and competitors. One mechanism that may be particularly important, and which is the focus of this review, is the role of climate in affecting the reproductive success of a predator through its effect on the relative timing of food requirement and food availability during early life stages. This principle — the match or mismatch of predators' requirement with resource availability — originated in the marine literature, where it ini- tially referred to how growth and survival of fish larvae (predator) depends on this production being synchronous with that of their main food items, i.e. early stage zooplankton (prey). Here we review how the match/mismatch hypothesis (MMH) is used to describe climate effects on ecological patterns and processes in both marine and terrestrial systems. In addition to studying match/mismatch sensu stricto, we expand on it to include effects of overall production level and the spatial aspect. Possible impacts of climate change on match/mismatch are examined in the context of one of the most appar- ent effects of global warming: an advancement of spring phenology. As a consequence of different species reacting dissimilarly, even minor changes in climate may invoke non-linear responses unbal- ancing established patterns of synchrony. All components of a food chain cannot be expected to shift their phenology at the same rate, and thus are unlikely to remain synchronous.

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Climate and the match or mismatch between predator requirements and resource availability

Climatic oscillations as reflected in atmospheric modes such as the North Atlantic Oscillation (NAO) may be seen as a proxy for regulating forces in aquatic and terrestrial ecosystems. Our review highlights the variety of climate processes related to the NAO and the diversity in the type of ecological responses that different biological groups can display. Available evidence suggests that the NAO influences ecological dynamics in both marine and terrestrial systems, and its effects may be seen in variation at the individual, population and community levels. The ecological responses to the NAO encompass changes in timing of reproduction, population dynamics, abundance, spatial distribution and interspecific relationships such as competition and predator-prey relationships. This indicates that local responses to large-scale changes may be more subtle than previously suggested. We propose that the NAO effects may be classified as three types: direct, indirect and integrated. Such a classification will help the design and interpretation of analyses attempting to relate ecological changes to the NAO and, possibly, to climate in general.

Ecological effects of the North Atlantic Oscillation

Rapid warming of Arctic marine ecosystems has led to a change in the spatial distribution of fish communities, with boreal communities expanding into regions previously dominated by Arctic fish species, which are now retracting northwards. Arctic marine ecosystems are warming twice as fast as the global average1. As a consequence of warming, many incoming species experience increasing abundances and expanding distribution ranges in the Arctic2. The Arctic is expected to have the largest species turnover with regard to invading and locally extinct species, with a modelled invasion intensity of five times the global average3. Studies in this region might therefore give valuable insights into community-wide shifts of species driven by climate warming. We found that the recent warming in the Barents Sea4 has led to a change in spatial distribution of fish communities, with boreal communities expanding northwards at a pace reflecting the local climate velocities5. Increased abundance and distribution areas of large, migratory fish predators explain the observed community-wide distributional shifts. These shifts change the ecological interactions experienced by Arctic fish species. The Arctic shelf fish community retracted northwards to deeper areas bordering the deep polar basin. Depth might limit further retraction of some of the fish species in the Arctic shelf community. We conclude that climate warming is inducing structural change over large spatial scales at high latitudes, leading to a borealization of fish communities in the Arctic.

Recent warming leads to a rapid borealization of fish communities in the Arctic

Ecosystem objectives in fisheries management usually flow from high-level national
policies or strategies and international agreements. Consequently they are often
broadly stated and hence are difficult to incorporate directly in management plans.
Predicting the results of any management action is very uncertain because the
dynamics of ecosystems are complex and poorly understood. Methods to design and
evaluate operational management strategies have advanced considerably in the past
decade. These management-strategy-evaluation (MSE) methods rely on simulation
testing of the whole management process using performance measures derived from
operational objectives. The MSE approach involves selecting (operational) management
objectives, specifying performance measures, specifying alternative management
strategies, and evaluating these using simulation. The MSE framework emphasizes the
identification and modelling of uncertainties, and propagates these through to their
effects on the performance measures. The framework is outlined and illustrated by
three ecosystem-related applications: management of benthic habitats and broad fish
community composition; by-catch of species of high conservation value; and foodchain
interactions and dependencies. Challenges to be overcome before broader
ecosystem-related objectives can be fully handled are discussed briefly.

http://archive.nefmc.org/tech/ebfm%20workshop/Sainsbury%20et.%20al.,%202000.pdf

Design of operational management strategies for achieving fishery ecosystem objectives

The widespread depletion of commercially exploited marine living resources is often seen as a general failure of management and results in criticism of contemporary management procedures. When populations show dramatic and positive changes in population size, this invariably leads to questions about whether favorable climatic conditions or good management (or both) were responsible. The Barents Sea cod (Gadus morhua) stock has recently increased markedly and the spawning stock biomass is now at an unprecedented high. We identify the crucial social and environmental factors that made this unique growth possible. The relationship between vital rates of Barents Sea cod stock productivity (recruitment, growth, and mortality) and environment is investigated, followed by simulations of population size under different management scenarios. We show that the recent sustained reduction in fishing mortality, facilitated by the implementation of a “harvest control rule,” was essential to the increase in population size. Simulations show that a drastic reduction in fishing mortality has resulted in a doubling of the total population biomass compared with that expected under the former management regime. However, management alone was not solely responsible. We document that prevailing climate, operating through several mechanistic links, positively reinforced management actions. Heightened temperature resulted in an increase in the extent of the suitable feeding area for Barents Sea cod, likely offering a release from density-dependent effects (for example, food competition and cannibalism) through prolonged overlap with prey and improved adult stock productivity. Management and climate may thus interact to give a positive outlook for exploited high-latitude marine resources.

https://www.pnas.org/content/pnas/111/9/3478.full.pdf

Synergies between climate and management for Atlantic cod fisheries at high latitudes

Padmini Dalpadado1*, Randi B. Ingvaldsen1, Leif Christian Stige2, Bjarte Bogstad1, Tor Knutsen1, Geir Ottersen3, and Bjornar Ellertsen1 Institute of Marine Research (IMR), PO Box 1870, 5817 Bergen, Norway Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, PO Box 1066, Blindern, N-0316 Oslo, Norway Institute of Marine Research, Gaustadalleen 21, 0349 Oslo, Norway *Corresponding author: tel: +47-55238439; fax: +47-55238555; e-mail: padmini.dalpadado@imr.no.

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Climate effects on Barents Sea ecosystem dynamics

Long time-series of data from the Barents Sea (BS) are analysed to contrast the climate, fishing pressure, plankton, pelagic fish, demersal fish, and interactions between trophic levels in a recent decade (2000–2009) with the period 1970–1999. During the past four decades, fishing pressure and climatic conditions have varied greatly in the BS, and stock levels have fluctuated substantially. Trophic control has changed from mainly bottom–up to top–down, then back to mainly bottom–up. No clear evidence for persistent ecological regimes was found. The past decade has been the warmest on record, with large stocks of demersal and pelagic fish, and increasing abundances of krill and shrimp. Except perhaps for the rather less-studied Arctic species, the short-term effect of the recent warming has been positive for BS stocks. However, as many of the long-established relationships and mechanisms in the BS seem to be changing, the long-term effects of warming are uncertain.

/pdf/changes-in-barents-sea-ecosystem-state-1970-2009-climate-4jswk8cv9l.pdf

Changes in Barents Sea ecosystem state, 1970 -2009: climate fluctuations, human impact, and trophic interactions

The Barents Sea capelin stock underwent drastic changes in stock size during the last three decades. Three stock collapses occurred in 1985–1989, 1993–1997, and 2003–2006. The collapses had effects both downwards and upwards in the food web. The release in predation pressure from the capelin stock led to increased amounts of zooplankton during the collapse periods. When capelin biomass was drastically reduced, its predators were affected in various ways. Cod experienced increased cannibalism, growth was reduced and maturation delayed. Sea birds experienced increased rates of mortality and total recruitment failures, and breeding colonies were abandoned for several years. Harp seals experienced food shortage, increased mortality because they invaded the coastal areas and were caught in fishing gears, and recruitment failures. There is evidence for differences in how the three capelin collapses affected the predators. The effects were most serious during the 1985–1989 collapse and can hardly be tra...

Ecosystem effects of the three capelin stock collapses in the Barents Sea

Stomach content data collected from cod caught during offshore resource assessment surveys in three Arcto-boreal ecosystems (the Barents Sea and the shelves off Iceland and eastern Newfoundland) were examined to determine the prevalence of cannibalism, and to identify possible factors associated with variability in prevalence. Cannibalism provides a minor source of food, except for the largest predators. Cannibalism Increases with predator length. Most prey are less than 40 cm In length and less than 3 years old. In each region, cannibalism occurs over most of the area surveyed, but is most prevalent where the smallest cod have been found in bottom trawl surveys. The frequency of occurrence of cannibalism recorded in recent years (late 1970s to the present) has usually been low (<I%) in all regions. Much higher values were reported from the Barents Sea in 1949-1960. In the Barents Sea, the frequency of occurrence of cannibalism increased with the abundance of juvenile cod. There was little support for the hypothesis that the frequency of cannibalism increased when the abundance of capelin, the major prey of cod, was low. It can be demonstrated that cod eat large numbers of their young, especially those of ages 0-2, but the mortality rate imposed cannot be calculated without independent estimates of the abundance of young cod. Mortality imposed by cannibalism and competition is estimated without stomach content data for Icelandic cod. This is done by modelling the change in abundance from the pelaglc 0-group stage, as measured by pelagic trawl surveys, to age 3, as estimated by VPA.

Bjarte Bogstad

Papers

Synergies between climate and management for Atlantic cod fisheries at high latitudes

Climate effects on Barents Sea ecosystem dynamics

Changes in Barents Sea ecosystem state, 1970 -2009: climate fluctuations, human impact, and trophic interactions

Ecosystem effects of the three capelin stock collapses in the Barents Sea

Cannibalism and year-class strength in Atlantic cod (Gadus morhua L.) in Arcto-boreal ecosystems (Barents Sea, Iceland, and eastern Newfoundland)