R. Ian Perry

Regime shifts in marine ecosystems: detection, prediction and management

Regime shifts are abrupt changes between contrasting, persistent states of any complex system. The potential for their prediction in the ocean and possible management depends upon the characteristics of the regime shifts: their drivers (from anthropogenic to natural), scale (from the local to the basin) and potential for management action (from adaptation to mitigation). We present a conceptual framework that will enhance our ability to detect, predict and manage regime shifts in the ocean, illustrating our approach with three well-documented examples: the North Pacific, the North Sea and Caribbean coral reefs. We conclude that the ability to adapt to, or manage, regime shifts depends upon their uniqueness, our understanding of their causes and linkages among ecosystem components and our observational capabilities.

Trophodynamic and advective influences on Georges Bank larval cod and haddock

Using a model-based approach, the relative effects of advective and trophodynamic (feeding and growth) processes are considered on populations of larval cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) on Georges Bank. Building on previous studies that describe the role of advection, this study incorporates trophodynamic relationships to examine starvation mortality and growth rates at the level of individual larvae on the Bank. Estimates of prey concentrations and flow fields appropriate for late winter/early spring are used. Both trophodynamic processes and advection influence larval losses from the Bank where, in the absence of starvation, advective losses are on the order of one-fifth of the eggs and larvae spawned on the Bank. Starvation is most important in the first feeding larvae and is much reduced for older larvae. The contact rates between larval fish and zooplankton prey when turbulence is included are 2–5 times greater than the contact rates with no turbulence, and allow the model cod larvae to achieve growth rates similar to those observed on the Bank, although mean rates for larval haddock are still lower than observed. Turbulence-enhanced contact rates are thus determined to be a necessary component in our description of the growth of cod and haddock larvae on Georges Bank. Model cod larvae with growth rates comparable to those observed in the field are located below the surface layer (deeper than 25 m) and inside the 60 m isobath. The region of highest retention due to circulation processes (Werner et al., 1993; Fisheries Oceanography, 2, 43–64) coincides with the region of highest growth rates and highest larval survival. Therefore, there is a complementary interaction between trophodynamic and circulation processes, with those larvae most likely to remain on the Bank also being those in the most favorable feeding regions. Haddock larvae require higher prey densities than cod larvae to survive.

Development of the green sea urchin (Strongylocentrotus droebachiensis) fishery in British Columbia, Canada — back from the brink using a precautionary framework

Abstract The development of the green sea urchin (Strongylocentrotus droebachiensis) fishery in British Columbia, Canada, is presented as an example of how a precautionary approach was applied to avert collapse of a developing invertebrate fishery and to rebuild towards a sustainable fishery. We consider four components: (1) identification of the appropriate spatial scales; (2) development of scientifically-supported management strategies; (3) consideration of uncertainties; and (4) collaborations amongst scientists, fishery managers, and stakeholders. The green sea urchin fishery in British Columbia has experienced three periods: a “developing” period during which effort and landings increased, but catch per unit of effort (CPUE) declined; a “crisis” period during which effort and landings peaked and CPUE reached a minimum; and a “rebuilding to sustainable” period during which landings and effort stabilised and CPUE increased. Passive management actions (minimum size limit, seasonal closures) were introduced at the beginning of the fishery, but were unable to limit exploitation. Subsequent to the crisis period, active management measures (large area closures, quotas, and an individual quota system) were implemented based on scientific studies and appear to have stabilised the fishery. The availability of fishing logbook information from the inception of the fishery and the development of positive relationships amongst all participants in the fishery were central elements of this rebuilding process. The long time series of logbook information provided sufficient data contrasts to use two surplus production modelling techniques to develop biological reference points for management regulations. The green sea urchin fishery is now a small but important, and apparently stable, component of the dive fisheries in British Columbia.

Comparative analysis of marine ecosystems: international production modelling workshop

Understanding the drivers that dictate the productivity of marine ecosystems continues to be a globally important issue. A vast literature identifies three main processes that regulate the production dynamics of such ecosystems: biophysical, exploitative and trophodynamic. Exploring the prominence among this ‘triad’ of drivers, through a synthetic analysis, is critical for understanding how marine ecosystems function and subsequently produce fisheries resources of interest to humans. To explore this topic further, an international workshop was held on 10–14 May 2010, at the National Academy of Sciences Jonsson Center in Woods Hole, MA, USA. The workshop compiled the data required to develop production models at different hierarchical levels (e.g. species, guild, ecosystem) for many of the major Northern Hemisphere marine ecosystems that have supported notable fisheries. Analyses focused on comparable total system biomass production, functionally equivalent species production, or simulation studies for 11 different marine fishery ecosystems. Workshop activities also led to new analytical tools. Preliminary results suggested common patterns driving overall fisheries production in these ecosystems, but also highlighted variation in the relative importance of each among ecosystems.

Larval development of Acantholithodes hispidus (Stimpson) (Decapoda: Anomura: Lithodidae) reared in the laboratory

Summary The complete larval development of Acantholithodes hispidus is described, based on rearing in the laboratory. The species has four zoeal stages plus one megalopa. Each stage is described and illustrated, and detailed comparisons are made with other lithodid crab larvae. A. hispidus zoea is markedly different from the previously described Lithodidae zoea in the shape of the carapace, rostral and posterolateral spines, abdomen and telson. A. hispidus zoea has morphological characters of the Brachyura and the Anomura.

A comparative appraisal of the resilience of marine social-ecological systems to mass mortalities of bivalves

In many parts of the world, both wild and cultured populations of bivalves have been struck by mass mortality episodes because of climatic and anthropogenic stressors whose causes and consequences are not always clearly understood. Such outbreaks have resulted in a range of responses from the social (fishers or farmers) and governing systems. We analyzed six commercial bivalve industries affected by mass mortalities using I-ADApT, a decision support framework to assess the impacts and consequences of these perturbations on the natural, social, and governing systems, and the consequent responses of stakeholders to these events. We propose a multidimensional resilience framework to assess resilience along the natural, social, and governing axes and to compare adaptive responses and their likelihood of success. The social capital and governability of the local communities were key factors affecting the communities’ resilience and adaptation to environmental changes, but the rapid degradation of natural ecosystems puts the bivalve industry under a growing threat. Bivalve mariculture and fishing industries are likely to experience increased frequency, severity, and prevalence of such mass mortality events if the resilience of the natural systems is not improved. An understanding of previous adaptation processes can inform strategies for building adaptive capacity to future events.

Larval development of the grooved tanner crab, chionoecetes tanneri rathbun, 1893 (decapoda: Brachyura: Majidae) described from the laboratory‐reared specimens

Abstract This paper documents the defining morphological characteristics of the larval stages of Chionoecetes tanneri Rathbun, 1893, the grooved Tanner crab, from specimens reared in the laboratory. Chionoecetes tanneri larval stages include two zoeae and one megalopa. The first zoea is characterized by: six setae on the posterior margin of the carapace; postero‐lateral spines on abdominal somites 3 and 4, extending beyond the posterior margin of adjacent somites and bearing 9–10 spinnules; 12 plumose setae and one stout distal plumose seta present on the margin of the scaphognathite of the maxilla; and one fused lateral spine and one articulated dorso‐medial spine on each fork of the telson. The second zoea is characterized by: 9 setae on the postero‐lateral margin of the carapace; a serrated mandible molar; a mandibular palp bud; 25–26 plumose setae on the margin of the scaphognathite of the maxilla; pereiopods with well‐developed gills and buds; and four pairs of stout setae on the posterior margin of the telson. For the megalopal stage, the distinguishing characteristics include: a rostral spine equal in length to the supraorbital spine; six setae on the exopod of the uropod; and a single spine on the ischium of the second pereiopod. This study allows C. tanneri larvae to be distinguished from the larvae of known sympatric congeners. This information provides a basic taxonomic tool for researchers in fisheries management and zooplankton ecology who are addressing issues related to trophic interactions, metapopulation dynamics and ecosystem impacts in the evolving marine resource management strategies in the North Pacific, and those related to Chionoecetes species in particular.