Mahima Jaini

Date of Award

5-2011

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Marine Biology

Advisor

Richard Wahle

Second Committee Member

Andrew Thomas

Third Committee Member

Andrew Pershing

Abstract

Recruitment to benthic marine populations is fundamentally a biophysical problem. The American Lobster Settlement Index is an annual diver-based survey of the young-of-year American lobsters (Homarus americanus) found in inshore nurseries in New England, USA and Atlantic Canada at the end of the postlarval settlement season. The considerable interannual variability in the settlement index suggests that environmental factors play an important role in regulating planktonic larval supply and transport. In this study, I focused on the longest settlement time series from three oceanographically contrasting regions: Midcoast Maine, coastal Rhode Island and the lower Bay of Fundy. Sampling in these regions was initiated in 1989, 1990 and 1991, respectively. I evaluated the correlation of inshore lobster settlement with sea surface temperature time series from satellites; wind data from buoys and land stations; and river discharge data from inland gauge stations. Correlations were performed between the annual lobster settlement indices and the monthly environmental metric with time lags up to three months prior to the month of settlement sampling, just before larvae hatch into the water column. Interannual variability in lobster settlement correlated strongly with SSTa and wind stress, but exhibited a weak association with river discharge. Statistically significant correlations were restricted to the two-month window when larvae and postlarvae are in the water column. Correlations of the settlement index with monthly satellite-derived sea surface temperature anomalies (SSTa) mapped to recognizable features on the sea surface. For example, the Rhode Island lobster settlement index correlated positively with SSTa found over Georges Bank up to two months prior to settlement sampling. Rhode Island settlement index also correlated with alongshore component of wind stress over Georges Bank for the month of settlement sampling. Midcoast Maine lobster settlement correlated weakly with sea surface temperature anomalies, but a strong positive correlation was found with alongshore wind stress during the month prior to settlement sampling. Only Midcoast Maine lobster settlement showed a negative association with local monthly river discharge. Bay of Fundy lobster settlement was positively correlated with sea surface temperature anomalies and cross-shore wind stress at two of the closest wind stations, one month prior to settlement sampling. In short, sea surface temperature anomalies and wind stress proved to be strong environmental correlates of lobster settlement in this analysis. All significant relationships consistently fell within two months of the settlement sampling, a time when larvae and postlarvae occupy the water column. These results suggest satellite SSTa data and wind data from multiple stations may be useful in predicting interannual fluctuations in lobster settlement, and therefore may lead to a better understanding of the mechanisms influencing recruitment variability.

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