Spatial and Temporal Distribution of Atlantic Menhaden Larvae Along the Atlantic Coast

Atlantic menhaden (Brevoortia tyrannus) larvae and environmental factors were sampled along the Atlantic coast from Maine to North Carolina in 1971-2008.   The abundance of Atlantic menhaden larvae showed large spatial and temporal variation with many zero observations (98.0%).  Within a total of 293 cruises, 78.5% of the total catch was sampled from September to November, and 64% of the total catch was taken in eight cruises- -five cruises in the 1980s (November –December 1983, November –December 1985, January-February 1986 and November –December 1986) and three in the 2000s (October-November 2001, September-October 2003, and October-November 2007).  The center of distribution was spatially variable.  In the 1980s, locations of the center of distribution showed larger spatial variation, spreading from the New Jersey to Virginia coasts. However, in the 2000s, locations of the center of distribution were confined to the Maryland and Delaware coasts.  A generalized additive model (GAM) was fitted to the survey data.  Results indicated that sea surface temperature (SST) and spatial factors were significantly correlated with the probability of positive observations.  Atlantic menhaden larvae were found in a relatively wide SST range (4 ~25°C), but the range with high positive catch probability is relatively narrow (7 ~12°C).  Probability of positive catch for the study area was then calculated using satellite derived SST data at 0.5 degree latitude by 0.5 degree longitude resolution.  The probability of positive catches of Atlantic menhaden larvae decreased in the 2000s relative to the 1980s.  However in some inshore area, the probability of positive catch in the 2000s was higher than in the 1980s.  The relationship between SST and menhaden larvae distribution likely is indicative of effects of climate change.