Date of Award

5-2009

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

Advisor

Robert S. Steneck

Second Committee Member

James A. Wilson

Third Committee Member

Theodore V. Willis

Abstract

Once abundant, alewives have continued to decline since the 1960s and today regulators list them as a "species of concern". Maine is the only New England state with an active alewife fishery, but its landings have also declined since the 1970s. This study examined river-specific catch rates as a proxy for abundance and examined three potential drivers of alewife population dynamics including, river fishing management, access to upriver spawning habitats and ocean fishing effects. For this, we studied four Mid-coast Maine Rivers (Medomak, St. George, Damariscotta and Orland rivers) and examined historical accounts of river fishing management and river barriers (dams) to determine if changes in abundance correspond to changes in any of these drivers. We found no significant relationship between access to spawning habitat and alewife landings for any of the rivers. In fact, watershed access for alewives increased or remained constant during the period of greatest declines in populations and landings. Importantly, synchronous declines in alewife abundance among three rivers studied from 1976-1980, suggest ocean effects may be controlling landings. Correspondence among declines in State of Maine and Damariscotta River catch rates and Gulf of Maine abundances from trawl surveys suggest that ocean effects may be controlling alewife populations. While fishing in the oceans likely reduced local alewife harvests, river fishing may also have contributed to the decline. We also consider how management impacted the alewife fishery. Increased State communication with municipalities provided local managers with a more regional perspective of the status of the fishery. With this additional information, towns reduced fishing effort and in some instances closed the fishery. Local management supported non-mandated closures and at times their decisions were more conservative than state recommendations. We found that local management was attuned to ecological feedback about the impact of human activity and managers used this information to adapt and change their behavior. Though local management is an important component of successful fisheries management, we argue that multi-level governance is essential to sound fisheries management. In spite of these conservation efforts, we found that other, non-local factors appear to be the dominant drivers of alewife abundance. While populations remain suppressed, they have increased slightly during the 1990s, suggesting possible relaxation of negative drivers of alewife populations in mid-coast Maine.

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