McBride et at: Interspecific comparisons of searobin, Prionotus spp., movements, size structure and abundance 
309 
highly variable (for northern searobins, 
CV=48 in spring and 49 in autumn; for 
striped searobins, CV= 68 in spring and 101 
in autumn; Fig. 8) but showed no clear trend 
over time. There was one notable period of 
decline for northern searobins during spring 
surveys throughout the 1970’s, but there was 
also a modest rebound in abundance during 
the 1980’s. The low values in the early 1990’s 
were similar to values measured in the late 
1960’s. The abundance of northern searobins 
during autumn cruises suggested no trend 
but was punctuated with sporadic peaks. 
Striped searobins also appeared to be more 
abundant during the 1970’s than in the 
1960’s or 1990’s, according to spring indices. 
The autumn time series for striped searobins 
declined overall, until the last year (1995), 
which showed a sudden increase. Abundance 
was compared between species to establish 
if each species’ population size followed simi- 
lar seasonal and interannual trends. Corre- 
lation analyses detected a significant rela- 
tion between northern and striped searobin 
annual indices measured in the spring sur- 
vey (Spearman rank correlation, r s =0.47, 
P=0.01, n=28), but the correlation between 
species abundance in the autumn surveys 
was not significant (r s =0.006, P= 0.97, n=24). 
The spring and autumn indices for a given 
year were not significantly correlated for 
northern searobins (r s =0.14, P=0.51, n- 24) 
but were significantly correlated for striped 
searobins (r s =0.65, P=0.0006, n= 24). These 
latter results suggested that the selected 
spring and autumn strata measured similar 
trends of abundance for striped searobins but not for 
northern searobins. 
Earlier estimates of searobin population size also 
noted considerable yearly variations in abundance. 
Clark and Brown (1977) reported a dramatic 97% 
decline in abundance (by weight) of searobins in the 
southern Mid-Atlantic region (also depicted in 
Grosslein [1976]) based on the same database dur- 
ing the period 1967-74. But they also reported a 
143% increase in abundance of searobins in the 
southern New England region. It is difficult to com- 
pare their results with our Figure 8 because they 
grouped northern and striped searobins together. 
They also used autumn collections from offshore 
strata sets, but our autecological analyses revealed 
these strata as only marginally appropriate, at least 
for striped searobins that are still inshore during 
autumn. Their analysis of abundance reviewed years 
during which fairly rapid change was occurring for 
both searobins and the groundfish assemblage in 
general, but our analyses demonstrate that searobin 
abundance has fluctuated up and down since the 
early 1970’s. 
Northern searobin annual abundance in the Mas- 
sachusetts coastal survey has also shown large long- 
term variations (Fig. 8). Modest increases for north- 
ern searobin abundance in the early 1990’s barely 
offset dramatic declines during the 1980’s. In con- 
trast, there was no trend in abundance of striped 
searobins during this 20-year period. These indices 
could be biased with respect to interannual varia- 
tions in coastal temperatures because Murawski 
(1993) demonstrated that the latitudinal range of 
northern searobins varied between years with respect 
to sea-temperature anomalies. Thus, one might ex- 
pect that searobins are more abundant in coastal 
Massachusetts waters during warmer years. Such 
does not appear to be the case, however, because 
