Lamkin: The Loop Current and abundance of larval Cubiceps pauciradiatus 
263 
cal input of upwelling regions, and adults will be con- 
centrated by increased abundances of prey (Atkinson 
and Targett,1983). Turbulent mixing is increased at 
frontal areas; therefore, formation and dissipation 
of prey patches will also be affected. A recent model 
by Davis et al. ( 1991) shows that formation and abun- 
dance of microscale patches (< 10 m) of prey can 
change the growth rate of larvae by up to 25%. Fron- 
tal regions, with convergent and divergent zones that 
result in biological gradients such as those found in 
the transects across the Loop Current, could be ex- 
pected to lead to patchiness both across and along 
the front. This model predicts that even small varia- 
tion in growth rates due to turbulence and patchi- 
ness can lead to large fluctuations in recruitment. 
In contrast, the years following 1983 were charac- 
terized by a less stable Loop Current structure, and 
fish abundances were considerably reduced. In 1984 
the Loop Current did not move north of 27°N until 
late March, only one month before the survey began 
(Fig 3). In 1986 the Loop was positioned well to the 
south, and little frontal habitat was available in the 
Gulf of Mexico to the spawning population (Figs. 4 
and 5). The pattern was similar in 1987 and 1988 
(Figs. 6-10). In both years the 22°C isotherm at 100 
m began well to the south of 27°N, before pushing 
north in the spring. 
It is not clear what factors are the important ones 
in driving such variations in abundance. Variance of 
fish populations is a natural occurrence and the sub- 
ject of many studies on recruitment. However, the 
pattern of abundance during these five years was 
not unique to C. pauciradiatus. Aggregation of blue- 
fin tuna (Thunnus thynnus), and billfish (Istio- 
phoridae) are also closely tied to the location of ther- 
mal fronts (Roffer, et al., 1994). These unrelated 
pelagic species showed similar trends in larval abun- 
dance with peaks in 1983 and with decreases there- 
after. Thunnus thynnus larval abundance closely par- 
alleled C. pauciradiatus abundance, even showing 
an increase in 1988. Ariomma melanum, another 
stromateoid, showed similar trends in larval abun- 
dance (Fig. 18). These fish are benthopelagic over 
the continental margin, and most adults are taken 
in bottom trawls at depths of 225-480 m. This cer- 
tainly indicates that the variation in the Loop Cur- 
rent position and stability may impact the abundance 
of a wide range of species and not just large pelagic 
predators such as bluefin and billfish. 
Although stability and size of the frontal system 
are important to frontal species, other physical-bio- 
logical interactions take place within the system on 
a variety of scales. The importance of each interac- 
tion will vary on time scales ranging from months to 
days because of the inherent nature of frontal sys- 
tems. Rothschild et al. (1989) states that it is neces- 
sary to consider the “mechanisms of population sta- 
bilization at each phase of the life history.” Although 
it has sometimes been possible to tie population fluc- 
tuations to a certain physical event (Harris et al., 
1992 ), it is more often the case that we are faced with 
a much more multidimensional problem. 
That large-scale oceanographic processes have a 
major influence on the abundance of fish stocks has 
been recognized by a variety of authors. Harris et al. 
(1988) reported on several species and presented 
evidence that large-scale changes in the distribution 
of southern bluefin tuna result from large-scale 
changes is SST. Koslow ( 1984) argued that large-scale 
physical forcing rather than ecological and biologi- 
cal interactions is the dominant factor controlling the 
recruitment of several northwest Atlantic fisheries. 
Basin-scale circulation patterns may be the driving 
