Bruce G. Hatcher

Chapter 18 Ecology of Strongylocentrotus droebachiensis

Publisher Summary This chapter discusses the ecology of Strongylocentrotus droebachiensis (S. droebachiensis). It is the most widely distributed member of the Strongylocentrotidae family and plays a key ecological role in determining the distribution and abundance of benthic macroalgae, particularly kelps. It is considered a pest in areas where intensive grazing destroys kelp habitat and limits production available to commercial species, such as lobster. S. droebachiensis has become a valued commodity and is now extensively fished and cultured for its roe in Northwest Atlantic and Northeast Pacific. All of these factors have combined to make S. droebachiensis one of the most studied sea urchin species. It has a broad arctic-boreal distribution. It is found in tide pools in the low intertidal zone, and it generally occurs on rocky substrata, such as bedrock outcrops, boulders, and cobbles. S. droebachiensis adjusts its metabolism and activity level to compensate for seasonal variations in sea temperature, which can range from −1 to 20°C. It is an omnivore, feeding on a great range of algae, invertebrates, and microbes. Two general processes interact to control the degree and pattern of aggregation of S. droebachiensis on natural seabeds: food availability and predation.

A stochastic approach to marine reserve design: Incorporating data uncertainty

Abstract Marine reserves, or protected areas, are used to meet an array of biodiversity and conservation objectives. The design of regional networks of marine reserves is concerned with the problem of where to place the marine protected areas and how to spatially configure them. Quantitative methods for doing this provide important decision support tools for marine managers. The central problem is to balance the costs and benefits of the reserve network, whilst satisfying conservation objectives (hence solving a constrained optimization problem). Current optimization algorithms for reserve design are widely used, but none allow for the systematic incorporation of data uncertainty and its effect on the reserve design solutions. The central purpose of this study is to provide a framework for incorporating uncertain ecological input data into algorithms for designing networks of marine reserves. In order to do this, a simplified version of the marine reserve design optimization problem is considered. A Metropolis–Hastings random search procedure is introduced to systematically sample the model solution space and converge on an optimal reserve design. Incorporation of the uncertain input data builds on this process and relies on a parametric bootstrapping procedure. This allows for the solution (i.e. the marine reserve design) to be expressed as the probability of any planning unit being included in the marine reserve network. Spatial plots of this acceptance probability are easily interpretable for decision making under uncertainty. The bootstrapping methodology is also readily adapted to existing comprehensive reserve design algorithms. Here, a preliminary application of the algorithm is made to the Mesoamerican Barrier Reef System (in the Caribbean Sea) based on satellite-derived and mapped conservation features (from Landsat).

Chapter 26 - Strongylocentrotus droebachiensis

Strongylocentrotus droebachiensis, the green sea urchin, has a broad Arctic-boreal distribution and is commonly associated with laminarian kelp. As an omnivorous grazer, its feeding capabilities and preferences have profound effects on the structure and dynamics of benthic communities. It exhibits an annual reproductive cycle and has planktrophic larval development. Growth and reproductive rates are largely dependent on the quantity and quality of available food. Larval behavior can influence patterns of dispersal in the plankton and settlement on the seabed, but the importance of predation or other agents of mortality at early life history stages is poorly understood. Fish and decapod crustaceans are major predators of larger juveniles and adults and may play an important role in population regulation. Strongylocentrotus droebachiensis is susceptible to acute and chronic infections by microbial pathogens and parasitic nematodes. In the northwest Atlantic, mass mortality during outbreaks of an amoebic disease can have profound impacts on sea urchin populations and ecosystem state. Green sea urchins have been extensively fished or cultured for roe since the late 1980s. Aquaculture research is contributing new knowledge of the nutritional and reproductive physiology of the species.

Condition-dependent migratory behaviour of endangered Atlantic salmon smolts moving through an inland sea

We used acoustic telemetry and biological sampling of Atlantic salmon smolts to reveal the migration tactics that fish use when migrating through a unique brackish sea ecosystem in Canada. We found an interacting effect of water temperature and fish condition that predicted whether fish migrated to sea.

The effect of environmental conditions on Atlantic salmon smolts’ (Salmo salar) bioenergetic requirements and migration through an inland sea

The timing of the juvenile Atlantic salmon ocean-entry is considered a critical stage in the species’ life-history. Entry into the ocean at suboptimal times can have negative survival impacts on entire smolt cohorts. Previous studies have identified smolt residency time in the Bras d’Or Lakes as highly variable and correlated with body condition. This study combines energetic modelling using Dynamic Energy Budget (DEB) theory with acoustic telemetry to mechanistically link smolt bioenergetics to their migration strategy within the Bras d’Or. This study examines two main questions: 1) what is the relationship between smolts’ bioenergetics and smolts’ migration strategy, and 2) what effect would warmer water temperature have on smolts’ energetic requirements? Simulation results indicate that smolts requiring more food are more likely to exit the Bras d’Or during the observation period. The results also suggest higher lake temperature would result in faster depletion of smolt energy reserves, which is predicted to favour smolts migrating to the ocean sooner.