NWA - Executive Summary

## 1 EXECUTIVE SUMMARY

### 1.1 Introduction

One of the fundamental rationales for the existence of marine science is to support research leading to a wise use of marine resources. While our basic knowledge of the ocean, its physics, and the nature of its ecosystems have progressed remarkably in the past few decades, our ability to provide reasonable advice as to the response of any fishery to the combination of exploitation and the effects of climate change is still rudimentary. This document provides the outline of a program required to make a quantum leap forward in this area using the best tools available to modern molecular biology, statistics, physical oceanography, acoustics and population biology. The target fisheries and region for study is the northwestern Atlantic shelf edge with its extremely productive banks.

The banks of the northwestern Atlantic such as the Grand Banks and Georges Bank have been exploited as one of the major fisheries resources on the globe since at least the 1500s. This trend has continued to the present, with 1988 New England landings of cod, scallops and pollock amounting to $133.4 million dollars. Combined, this is approximately equal to the value of the lobster harvest for that period. The groundfish on Georges Bank are at their lowest stock size since estimates were begun. A rise in populations of pelagic species such as dogfish and skates suggests that the place which groundfish hold in the ecosystem may be being replaced. Furthermore, the most recent National Marine Fisheries Service report on the status of fishery resources off the northeastern United States concludes in the case of scallops that "current fishing effort is far beyond what the resource can sustain." Much of the stock decline is due to the effects of overexploitation. The effects of fishing on stocks, are, however, strongly influenced by variations in the physical and biological environment within which the fishery exists.

Climatic effects on fisheries have been reasonably well established in a number of regions although the exact processes by which these effects occur are not well understood in any situation. It is also well established that climate variations can substantially modulate the influence of exploitation and, within the extremes suggested in the recent climate record, can completely eliminate regional fisheries without any effects of fishing. These climatic variations range from the effects of the last ice age, which probably reduced the viable habitat for the species mentioned above by up to 90% through a combination of lowering temperature, salinity, and sea level and increases in sea ice cover; to historically documented decadal time scale fluctuations in winds, sea temperature and salinity that have a correlation with cod stock declines in recent decades. There is ample evidence for a broad range of climatic fluctuations in the past and some grave doubts about future variations tied to natural cycles and the effect of man through greenhouse warming and modifications to the marine environment tied to pollution.

In order to extract an understanding of the interactions between the physical environment, the primary and secondary producers in the marine ecosystem and the higher trophic level species relevant to commercial fisheries, a multidisciplinary approach is necessary. The GLOBEC Canada/U.S. Meeting on Northwest Atlantic Fisheries and Climate was held to consider the advent of such a multidisciplinary program on Georges Bank, and to recommend specific scientific elements which might be included in a full-fledged field program under the aegis of GLOBEC during the early 1990s. The following recommendations are intended to serve as guidelines, not as mandates, for formulation and implementation of the field study. These were made with strong consideration given to the ten necessary criteria for GLOBEC study sites.

### 1.2 Site Selection

Georges Bank is an ideal location in which to study the potential effect of global climate change on marine planktonic populations. Global climate models predict that significant changes are likely to take place there. The banks along the edge of North America from Georges Bank to the Grand Banks sit at the edge of the boundary between the subpolar and subtropical gyres. They are therefore sensitive to fluctuations in the current systems - the Gulf Stream and Labrador Currents - which form this boundary. Variations in these current systems are likely to be some of the strongest signals expected as part of global climate change.

### 1.3 Fish

Target species should emphasize cod and include haddock. Local populations should be defined by frequent surveys, molecular and biochemical techniques, with a focus on locating key spawning sites. A key objective of population dynamics is to study the development of larvae with respect to the onset of seasonal vertical stratification. Process studies should focus on mechanisms controlling population dynamics, such as how food and feeding may change with climate, how adults locate spawning sites, and how the population is retained or exported from the area. Historical data should be exploited to a greater degree. A Historical Data Working Group should be established to make quality data sets available to the community; paleoecological studies should be encouraged. Modeling is particularly required for understanding the physical dynamics of Georges Bank, annual energy budgets of the target species, distinguishing between the effects of fishing pressure and climate change, and as a means to improve statistical techniques. New technology is needed to improve hardware and software for hydroacoustics, and to develop a variety of techniques relying on biochemistry and molecular biology to provide indices of physiological state such as growth, feeding, and reproduction.

### 1.4 Zooplankton

Target species should emphasize Calanus finmarchicus and include Pseudocalanus spp. and Centropages spp. Local populations of Calanus' are thought to overwinter in the nearby Gulf of Maine; the dynamics of their spring-time advection onto Georges Bank should be studied in detail. Population dynamics studies should focus on understanding reproduction, growth and mortality in relation to physical transport processes. Process studies should be aimed at understanding how local physics controls the distribution of zooplankton, and what processes control overwintering. Historical data are not as abundant as for fish, but are sufficient to determine the magnitude of signal required to detect effects of climate change. Modeling studies could make new sampling technology (e.g., acoustics and optics) more effective by helping to understand the relation between animal size and physiology; population dynamics could be better understood through coupled biological/physical numerical modeling. New technology is needed to rapidly assess physiological state, and to rapidly sample distributions of zooplankton from both moored and mobile platforms.

### 1.5 Benthos

Target species should include sea scallops (Placopecten magellanicus), but the focus might best be on types of meroplanktonic larvae and types of benthic habitat. Local populations could be studied by comparing a variety of larval types (e.g., feeding vs. non-feeding larvae, spring vs. fall spawners). Population dynamics studies should focus on larval dynamics of any species which might produce distinguishable cohorts of easily identifiable larvae from a well defined adult population, and should not necessarily be restricted to scallops. Process studies should focus on understanding the relation between fundamental population dynamics parameters (e.g., growth, reproduction) and physical and biological forcing functions such as tides, storms, food availability and temperature change. Historical data are less abundant than for other groups, but efforts should be undertaken to use what data do exist. Modeling studies could help to understand how local physical processes favor different reproductive strategies, what causes interannual variation in scallop recruitment, and how changing physical and biological factors affect larval life histories. New technology is acutely needed to rapidly sample and identify larvae of different species.

### 1.6 International Interactions

GLOBEC activities should be coordinated with existing international studies including WOCE, NOAA's Atlantic Climate Change Program (ACCP), and the Joint Global Ocean Flux Study (JGOFS). The Georges Bank initiative should be closely coupled with two new Canadian programs; these are the Ocean Production Enhancement Network (OPEN), a $25.4M, four-year program focusing on cod and scallops in the waters off Nova Scotia and Newfoundland and in the Gulf of St. Lawrence, and the Northern Cod Science Program (NCSP), a $43M program focused on fisheries oceanography off northern Newfoundland and the Labrador coast. An ICES working group on Cod and Climate Change (CCC) and the new SCOR working group on pelagic biogeography present opportunities for broadening GLOBEC's activities across the North Atlantic.

### 1.7 Field Program Logistics

The group endorsed a broad outline of a field program involving three basic means of studying Georges Bank: (1) Bank-scale survey cruises, (2) Process-oriented cruises, and (3) Moorings The recommended program would be carried out over a three-year period, with most effort focused in the first and third years.

The next step in the implementation process will involve the establishment of an implementation committee to provide the details of setting up a U.S. experiment. It is hoped that this will take place over the next year and come up with a plan for a program starting in the 1992-1993 time frame.