282 
The effects of temperature on hatching 
and survival of northern rock sole larvae 
(Lepidopsetta polyxystra) 
Abstract — Northern rock sole (Lepi- 
dopsetta polyxystra) is a commercially 
important flatfish in Alaska and 
was recently classified as a distinct 
species from southern rock sole (L. 
bilineata) . Taxonomic and vital rate 
data for northern rock sole are still 
not fully described, notably at early 
egg and larval stages. In this study, 
we provide new taxonomic descrip- 
tions of late-stage eggs and newly 
hatched larvae, as well as temper- 
ature-response models of hatching 
(timing, duration, success), and larval 
size-at -hatch and posthatch survival 
at four temperatures (2°, 5°, 9°, and 
12°C). Time-to-first-hatch, hatch cycle 
duration, and overall hatching success 
showed a negative relationship with 
temperature. Early hatching larvae 
within each temperature treatment 
were smaller and had larger yolk 
sacs, but larvae incubated at higher 
temperatures (9° and 12°C) had the 
largest yolk reserves overall. Despite 
having smaller yolks, size-at-hatch 
and the maximum size achieved 
during the hatching cycle was highest 
for larvae reared at cold temperatures 
(2° and 5°C), indicating that endog- 
enous reserves are more efficiently 
used for growth at these tempera- 
tures. In addition, larvae reared at 
high temperatures died more rapidly 
in the absence of food despite having 
more yolk reserves than cold-incu- 
bated larvae. Overall, northern rock 
sole eggs and larvae display early life 
history traits consistent with cold- 
water adaptation for winter spawning 
in the North Pacific. 
Manuscript submitted 8 February 2011. 
Manuscript accepted 1 April 2011. 
Fish. Bull. 109:282-291 (2011). 
The views and opinions expressed 
or implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National Marine 
Fisheries Service, NOAA. 
Benjamin J. Laurel (contact author)' 
Deborah M. Blood 2 
Temperature is arguably the most 
important environmental influence 
driving development, growth, and 
survival of marine fish during their 
early life history (Pepin, 1991). In 
cold water marine systems, small 
fluctuations in temperature can have 
profound effects on an individual’s 
vital rates, which at the population 
level can mediate connectivity pat- 
terns (Laurel and Bradbury, 2006; 
O’Connor et al., 2007), genetic struc- 
ture (Bradbury et al., 2010), cohort 
survival, and eventual recruitment 
to the adult fish population (Houde, 
2008). However, beyond the general 
positive relationships between tem- 
perature and poikilothermic metabo- 
lism ( Jobling, 1997), the temperature 
response for fish is highly variable 
among species and populations, 
necessitating the measurement of 
temperature effects on a species-by- 
species basis. In commercially har- 
vested species, this information is 
useful for estimating spawning stock 
biomass (using daily egg production 
methods; DEPM; Pena et al., 2010), 
measuring larval mortality (Pepin, 
1991), and predicting recruitment 
(Houde, 2008). 
Northern rock sole (Lepidopsetta 
polyxystra) is a commercially har- 
vested marine fish in Alaskan wa- 
ters and was recently classified as 
a distinct species from southern 
! 
rock sole (L. bilineata) (Orr and 
Matarese, 2000). Northern rock 
sole spawn earlier in the year (mid- 
winter) compared to southern rock 
sole (summer) in the region around 
Kodiak Island (Stark and Somerton, 
2002). Pertseva-Ostroumova (1961) 
reported peak spawning of northern 
rock sole (as Lepidopsetta bilineata 
bilineata ) off the east coast of Ka- 
mchatka from late March to early 
April and described egg and larval 
development at temperatures averag- 
ing 2.9-3.5°C. However, temperature 
effects on growth, mortality, and 
behavior have been principally re- 
stricted to the postsettlement phase 
(Hurst and Duffy, 2005; Laurel et 
al., 2007; Hurst et al., 2010). The egg 
and larval phases of eastern Bering 
Sea and Gulf of Alaska northern rock 
sole remain poorly understood, with 
the exception of descriptive studies 
on the taxonomy and distribution of 
Lepidopsetta spp. (Matarese et al., 
1989, 2003; Orr and Matarese, 2000; 
Lanksbury et al., 2007). 
The Gulf of Alaska and Bering Sea 
are experiencing extensive changes 
in environmental conditions, which 
in turn have affected seasonal tem- 
perature, ice extent, and larval prey 
production (Hunt et al., 2002). These 
changes raise concerns on how north- 
ern rock sole will respond directly to 
such environments. Developmental 
Email address for contact author: ben.laurel@noaa.gov 
1 Fisheries Behavioral Ecology Program 
Hatfield Marine Science Center 
Alaska Fisheries Science Center 
National Marine Fisheries Service 
2030 SE Marine Science Drive 
Newport, Oregon 97365 
2 Resource Assessment and Conservation Engineering Division 
Alaska Fisheries Science Center 
National Marine Fisheries Service 
7600 Sand Point Way N. E. 
Seattle, Washington 98115 
