Mariano Koen-Alonso

Bottom-Up Regulation of Capelin, a Keystone Forage Species

The Northwest Atlantic marine ecosystem off Newfoundland and Labrador, Canada, has been commercially exploited for centuries. Although periodic declines in various important commercial fish stocks have been observed in this ecosystem, the most drastic changes took place in the early 1990s when the ecosystem structure changed abruptly and has not returned to its previous configuration. In the Northwest Atlantic, food web dynamics are determined largely by capelin (Mallotus villosus), the focal forage species which links primary and secondary producers with the higher trophic levels. Notwithstanding the importance of capelin, the factors that influence its population dynamics have remained elusive. We found that a regime shift and ocean climate, acting via food availability, have discernible impacts on the regulation of this population. Capelin biomass and timing of spawning were well explained by a regime shift and seasonal sea ice dynamics, a key determinant of the pelagic spring bloom. Our findings are important for the development of ecosystem approaches to fisheries management and raise questions on the potential impacts of climate change on the structure and productivity of this marine ecosystem.

Operationalizing integrated ecosystem assessments within a multidisciplinary team: lessons learned from a worked example

Operationalizing integrated ecosystem assessments within a multidisciplinary team: lessons learned from a worked example Geret S. DePiper*, Sarah K. Gaichas, Sean M. Lucey, Patricia Pinto da Silva, M. Robin Anderson, Heather Breeze, Alida Bundy, Patricia M. Clay, Gavin Fay, Robert J. Gamble, Robert S. Gregory, Paula S. Fratantoni, Catherine L. Johnson, Mariano Koen-Alonso, Kristin M. Kleisner, Julia Olson, Charles T. Perretti, Pierre Pepin, Fred Phelan, Vincent S. Saba, Laurel A. Smith, Jamie C. Tam, Nadine D. Templeman, and Robert P. Wildermuth NOAA Northeast Fisheries Science Center, 166 Water Street, Woods Hole, MA 02543, USA Fisheries and Oceans Canada, Northwest Atlantic Fisheries Centre, 80 East White Hills, St. John’s, NL A1C 5X1, Canada Fisheries and Oceans Canada, Bedford Institute of Oceanography, 1 Challenger Drive, Dartmouth, NS B2Y 4A2, Canada School for Marine Science & Technology, University of Massachusetts Dartmouth, 200 Mill Road, Suite 30, Fairhaven, MA 02719, USA Environmental Defense Fund, Floor 28, 123 Mission Street, San Francisco, CA 94105, USA National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Northeast Fisheries Science Center, Geophysical Fluid Dynamics Laboratory, Princeton University Forrestal Campus, 201 Forrestal Road, Princeton, NJ 08540, USA

Growth and condition in relation to the lack of recovery of northern cod

Growth and condition in fishes have been taken as indicating levels of energy available for survival and reproduction, major components of a population’s productivity. After a rapid collapse in population size, northern (NAFO Division 2J3KL) cod (Gadus morhua) remained at a very low level of abundance for 20 years. We investigated the potential for poor growth and condition to have played a role in the collapse and lack of recovery of northern cod. Juveniles and adult males and females all showed similar patterns. Perceptions about the importance of growth and condition to population status depended on the metrics and area examined. When the northern cod population was declining, the northern areas of the population clearly had reduced growth and condition, while these metrics improved in the south. Results were equivocal as to the potential role of growth and condition in the continued low abundance of northern cod and, to some extent, depended on the nature of the metric being examined. Indices of condition, which included lipid storage in the form of liver weight, were generally lower in the north while the stock remained at a low level. Metrics associated with longer-term protein storage returned to precollapse levels quickly following the period of collapse. An index of food availability was more closely related to growth and condition than was temperature. These results point to the need both for studies of growth and condition in a population to have a comprehensive time-series of data covering the entire range of the population and the need for a better understanding of the causes and implications of changes in different metrics of condition.

Explanatory Power of Human and Environmental Pressures on the Fish Community of the Grand Bank before and after the Biomass Collapse

Ecosystem based fisheries management will benefit from assessment of how various pressures affect the fish community, including delayed responses. The objective of this study was to identify which pressures are most directly related to changes in the fish community of the Grand Bank, Northwest Atlantic. These changes are characterized by a collapse and partial recovery of fish biomass and shifting trophic structure over the past three decades. All possible subsets of nine fishing and environmental pressure indicators were evaluated as predictors of the fish community structure (represented by the biomasses of six fish functional-feeding groups), for periods Before (1985 – 1995) and After (1996 – 2013) the collapse, and the Full time series. We modelled these relationships using redundancy analysis, an extension of multiple linear regression that simultaneously evaluates the effect of one or more predictors on several response variables. The analysis was repeated with different lengths (0 to 5 years) and types (moving average vs. lags) of time delays imposed on the predictors. Both fishing and environmental indicators were included in the best models for all types and length of time delays, reinforcing that there is no single type of pressure impacting the fish community in this region. Results show notable differences in the most influential pressures Before and After the collapse, which reflects the changes in harvester behavior in response to the groundfish moratoria in the mid-1990s. The best models for Before the collapse had strikingly high explanatory power when compared to the other periods, which we speculate is because of changes in the relationships among and within the pressures and responses. Moving average predictor sets generally had higher explanatory power than lagged sets, implying that trends in pressures are important for predicting changes in the fish community. Assigning a carefully chosen delay to each predictor further improved the explanatory power, which is indicative of the complexity of interactions between pressures and responses. Here we add to the current understanding of this ecosystem while demonstrating a method for selecting pressures that could be useful to scientists and managers in other ecosystems.