Episodic downwelling predicts recruitment of Atlantic cod, Greenland cod and white hake to Newfoundland coastal waters

Recruitment in marine fish is influenced by abiotic and biotic processes operating at many spatial and temporal scales. Annual recruitment to fisheries has received more attention at the scale of the population than at finer temporal scales, where spatially heterogeneous biological processes modify year-class success. We tested two hypotheses: (1) that recruitment of marine fish to the nearshore benthos at a fine temporal scale is determined by downwelling associated with onshore winds and (2) that fish arrival nearshore is related to tidal stage. During summer and autumn 1998 to 2001 and late spring to autumn 2002, we monitored recruitment of Atlantic cod (Gadus morhua), Greenland cod (Gadus ogac) and white hake (Urophycis tenuis) to benthic habitats at 12 sites in Newman Sound, Newfoundland every two weeks using seine nets. Seining was conducted daily at an additional site nearby for approximately two months during 2002. There were sufficient data to identify four to six annual recruitment pulses of Atlantic cod during 1999 to 2002. Greenland cod and white hake were found to recruit only once annually during 1998 to 2002. Winds were mostly offshore during the periods studied. During this same period recruitment of Atlantic cod (18 events), Greenland cod (5 events) and white hake (5 events) was found to begin on days with onshore winds or within three days following onshore wind events. Results were consistent with onshore larval transport and settlement during downwelling events. Recruitment of Atlantic cod, Greenland cod and white hake to the nearshore benthos was not associated with tidal stage. Upwelling dynamics may affect both the timing and the magnitude of recruitment of many other benthic species occupying the coastal zone