Benthic invertebrates that form habitat on deep banks off southern California, with special reference to deep sea coral

There is increasing interest in the potential impacts that fishing activities have on megafaunal benthic invertebrates occurring in continental shelf and slope ecosystems. We examined how the structure, size, and high-density aggregations of invertebrates provided structural relief for fishes in continental shelf and slope ecosystems off southern California. We made 112 dives in a submersible at 32−320 m water depth, surveying a variety of habitats from high-relief rock to flat sand and mud. Using quantitative video transect methods, we made 12,360 observations of 15 structure-form-ing invertebrate taxa and 521,898 individuals. We estimated size and incidence of epizoic animals on 9105 sponges, black corals, and gorgonians. Size variation among structure-form-ing invertebrates was significant and 90% of the individuals were <0.5 m high. Less than 1% of the observations of organisms actually sheltering in or located on invertebrates involved fishes. From the analysis of spatial associations between fishes and large invertebrates, six of 108 fish species were found more often adjacent to invertebrate colonies than the number of fish predicted by the fish-density data from transects. This finding indicates that there may be spatial associations that do not necessarily include physical contact with the sponges and corals. However, the median distances between these six fish species and the invertebrates were not particularly small (1.0−5.5 m). Thus, it is likely that these fishes and invertebrates are present together in the same habitats but that there is not necessarily a functional relationship between these groups of organisms. Regardless of their associations with fishes, these invertebrates provide structure and diversity for continental shelf ecosystems off southern California and certainly deserve the attention of scientists undertaking future conservation efforts.

The relationship between smolt and postsmolt growth for Atlantic salmon (Salmo salar) in the Gulf of St. Lawrence

The interaction of ocean climate and growth conditions during the postsmolt phase is emerging as the primary hypothesis to explain patterns of adult recruitment for individual stocks and stock complexes of Atlantic salmon (Salmo salar). Friedland et al. (1993) first reported that contrast in sea surface temperature (SST) conditions during spring appeared to be related to recruitment of the European stock complex. This hypothesis was further supported by the relationship between cohort specific patterns of recruitment for two index stocks and regional scale SST (Friedland et al., 1998). One of the index stocks, the North Esk of Scotland, was shown to have a pattern of postsmolt growth that was positively correlated with survival, indicating that growth during the postsmolt year controls survival and recruitment (Friedland et al., 2000). A similar scenario is emerging for the North American stock complex where contrast in ocean conditions during spring in the postsmolt migration corridors was associated with the recruitment pattern of the stock complex (Friedland et al., 2003a, 2003b). The accumulation of additional data on the postsmolt growth response of both stock complexes will contribute to a better understanding of the recruitment process in Atlantic salmon.

Catch and Bycatch in the Shark Drift Gillnet Fishery off Georgia and East Florida

An observer program of the shark drift gillnet fishery off the Atlantic coast of Florida and Georgia was begun in 1993 to define the fishery and estimate bycatch including bottlenose dolphin, Tursiops truncatus, and sea turtles. Boats in the fishery were 12.2-19.8 m long. Nets used were 275-1,800 m long and 3.2-4.1 m deep. Stretched-mesh sizes used were 12.7-29.9 cm. Fishing trips were usually <18 h and occurred within 30 n.mi. of port. Fishing with an observer aboard occurred between Savannah, Ga., and Jacksonville, Fla., and off Cape Canaveral, Fla. Nets were set at least 3 n.mi. offshore. Numbers of boats in the fishery increased from 5 in 1993 to 11 in 1995, but total trips decreased from 185 in 1994 to 149 in 1995. During 1993-95, 48 observer trips were completed and 52 net sets were observed. No marine mammals were caught and two loggerhead turtles, Caretta caretta, were caught and released alive. A total of 9,270 animals (12 shark, 21 teleost, 4 ray, and 1 sea turtle species) were captured. Blacknose, Carcharhinus acronotus; Atlantic sharpnose, Rhizoprionodon terraenovae; and blacktip shark, C. limbatus), were the dominant sharks caught. King mackerel, Scomberomorus cavalIa; little tunny, Euthynnus alleteratus; and cownose ray, Rhinoptera bonasus, were the dominant bycatch species. About 8.4% of the total catch was bycatch. Of the totals, 9.4% of the sharks and 37.3% ofthe bycatch were discarded.