LeClair et al.: Seasonal changes in abundance and migration of Sebastes auriculatus and 5. caurinus 
311 
Table 3 
Maximum and mean daily temperature (t) (°C) changes (At) by season recorded at the near- and offshore reef margins of 
Point Heyer Artificial Reef, Puget Sound, WA, during 2006-2007. SD=standard deviation. 
Spring Summer Fall Winter 
24 hr max. Mean daily 24 hr max. Mean daily 24 hr max. Mean daily 24 hr max. Mean daily 
Reef margin 
At 
At (SD) 
At 
At (SD) 
At 
At (SD) 
At 
At (SD) 
Nearshore 
2.2 
0.7 (0.44) 
2.1 
0.8 (0.44) 
1.1 
0.3 (0.21) 
1.1 
0.2 (0.22) 
Offshore 
1.6 
0.4 (0.31) 
1.7 
0.6 (0.32) 
0.6 
0.2 (0.14) 
0.8 
0.2 (0.19) 
and thus was not a factor in assessing relative changes 
in abundance. Tides were also not judged to be a factor 
because the numbers of summer and winter surveys 
by tide cycle were not substantially different. Although 
rockfish are popular among Puget Sound anglers, rec- 
reational harvest was considered an unlikely source of 
bias, and commercial rockfish harvest is prohibited in 
central Puget Sound. From spring of 2005 through fall 
of 2006 the reef was closed to all rockfish retention. 
From fall of 2006 through spring of 2010, the rockfish 
season and retention rules were highly restrictive in 
Puget Sound, and PHAR attracted very few anglers. 
The minimal harvest that did occur took place dur- 
ing the summer, when rockfish abundance was high- 
est. Since May of 2010, recreational rockfish retention 
throughout nearly all of Puget Sound, including PHAR 
and adjacent waters, has been prohibited. Effects from 
potential diel movements were also dismissed as a 
source of bias in estimating rockfish densities because 
all surveys were conducted approximately halfway be- 
tween sunrise and mid-day. 
Moulton (1977) observed a winter decrease in copper 
rockfish densities over the course of scuba surveys of 
nearshore rocky reefs in north Puget Sound. On the ba- 
sis of seasonal density differences, over multiple depth 
strata, he concluded that over-wintering in deeper wa- 
ter beyond the survey range of his study was the most 
likely explanation. Richards (1987), observing a simi- 
lar trend over rocky habitats, offered an alternative 
explanation. She postulated that reduced activity and 
more cryptic behavior by copper rockfish during winter 
months can lead to lower abundance estimates from 
scuba surveys over rocky habitat. This hypothesis is 
consistent with Patten’s ( 1973 ) observation that copper 
rockfish on a small low-relief rocky reef in Puget Sound 
were more thigmotactic in the winter and spring. Simi- 
lar behavior has been noted for dusky (S. ciliates) and 
yellowtail (S. flavidus) rockfish surveyed by scuba div- 
ers in southeast Alaska (Carlson and Barr, 1977). In 
reference to Richards’ (1987) observation, Matthews 
(1990c) noted that winter decreases in brown and 
copper rockfish abundance had been observed in the 
nearshore environment of Puget Sound over sparsely 
vegetated low-relief reefs and sandy-bottom habitat, 
where hiding space is limited or nonexistent. The same 
author, however, also reported that brown and copper 
rockfish were more reclusive on high-relief reefs during 
the winter (Matthews, 1990a). 
To ensure that our observed winter decreases in 
abundance were not due to fish moving into the inter- 
stices of the reef and beyond our vision, divers equipped 
with digging and prying tools searched for fish by ex- 
cavating several off-transect boulder and cobble sites 
during the winter months. The excavations occasion- 
ally revealed rockfish that could have gone unnoticed 
with the use of our standard survey method, but the 
encounters were rare and we do not believe that they 
occurred with enough frequency to explain the marked 
decreases in abundance we observed during the win- 
ter. Also, several surveys, with roving divers covering 
distances of up to 2.5 km of the nearshore waters ad- 
jacent to and on either side of PHAR, were conducted 
during the winter in order to ascertain whether winter 
decreases in abundance might have been due to fish 
moving off the reef but remaining nearby within the 
same depth strata. No rockfish were encountered dur- 
ing any of these off-reef surveys. It was also possible 
that fish may have been crowding the deepest parts of 
the reef (beyond our maximum survey depth) during 
the winter. We conducted several winter dives along 
the deep offshore margin of the reef and found no evi- 
dence to indicate that fish remained, though at greater 
depths than those surveyed, on or near the reef during 
the winter. 
For some fish species, seasonal changes in abun- 
dance may be attributed to an infiux of juveniles that 
leads to higher counts during certain times of the year 
(Allen and Horn, 1975; Relini et al., 1994, Allen et al., 
2002, Barreiros et al., 2004). In our study, although the 
proportion of juvenile brown rockfish was significantly 
greater in the summer, juveniles of both species (length 
<10 cm) accounted for a very small proportion of the 
overall counts by season. Young-of-the-year fish made 
up an even smaller proportion because the <10 cm 
length class would have included some fish that were 
greater than 1 year in age. We conclude that the sea- 
sonal changes in abundance that we observed were not 
due to juvenile recruitment. The higher overall num- 
ber of copper than brown rockfish juveniles observed 
during the spring, summer, and fall is likely due to 
