Lamkin: The Loop Current and abundance of larval Cubiceps pauciradiatus 
259 
-96 
1986). Large filaments of warm 
Loop Current water are advected 
north as much as 300 km in the 
flow confluence of cold-ring and 
Loop Current interactions. These 
cyclonic rings were noted in every 
survey and the biologically fine 
structure of one of these was 
sampled in transect V. Analysis of 
satellite SST images shows that at 
least one and often two cold per- 
turbations are generally present 
along the northern edge of the 
Loop Current and along the west 
Florida shelf. 
The formation and circulation 
patterns are not completely under- 
stood, but other authors have ex- 
amined similar features else- 
where. In the western North At- 
lantic, Pollard and Regier (1990) 
described the structure and vari- 
ability of the upper 300-m of 
fronts. They found that small-scale 
eddies, tens of kilometers in width, 
may have vertical velocities as 
large as tens of meters a day and 
may approach 50 m/d. Trantor et 
al. (1983) suggested that in the 
Tasman Sea, an upwelling-down- 
welling circulation cell existed at 
the interface between a cyclonic 
crescent of cool water and an anti- 
cyclonic ring. They reported high 
concentrations of surface chloro- 
phyll, surface nitrate, and the 
copepod Calinoides carcinatus of- 
ten associated with upwellings 
along the edge of a warm core eddy 
in the cool crescent. Both of these 
mechanisms act to inject nutrients 
into the photic zone. However, 
whether there is a direct effect of 
these cold-core eddies on larvae and 
zooplankton of Gulf of Mexico 
stocks is not clear. Plankton dis- 
placement volume and larval abun- 
dances are larger, especially in the area between the 
ring and Loop Current. 
Transect V, which apparently bisected a cyclonic 
ring, had plankton displacement volumes higher than 
those of any of the other five tran sects (202 mL/1,000 
m). The cold-core rings found to the south are usu- 
ally associated with increased abundances of both zoo- 
plankton and larvae. Maul et al. (1984) found that a 
-94 
-92 
-90 
-88 
-86 
-84 
Figure 1 3 
Diagram of transects across the Loop Current in 1987 leg 2. 
cold ring that persisted for several months off the Dry 
Tortugas was associated with a 3-fold increase in catch 
per unit of effort of Atlantic bluefin tuna. A cyclonic 
ring was present in this position in 1983, 1984, and 
1988. In fact, in 1983 the highest catches of C. 
pauciradiatus ( 188 under 10m 2 ) were found near this 
feature along with elevated plankton displacement vol- 
ume and larval abundance. 
