291 
National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
rcr established in 1881 «<■- 
Spencer F. Baird 
First U S Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
A comparison of length distributions of rockfishes 
{Sebastes spp.) from submersible and trawl 
surveys off central California 
Email address for contact author: diana.watters@noaa.gov 
Abstract— Data from the West Coast 
Bottom Trawl Survey and from sur¬ 
veys conducted with a manned sub¬ 
mersible in nearby untrawlable 
areas were used to compare length 
distributions for greenspotted rock- 
fish (Sebastes chlorostictus), green- 
striped rockfish {S. elongatus), ca¬ 
nary rockfish (S. pinniger), and 
vermilion rockfish (S. miniatus) off 
central California. For all 4 species, 
broader size ranges and greater pro¬ 
portions of small fish were present 
in the data from the submersible 
surveys, and length distributions 
were significantly different (P<0.01) 
in comparisons of all lengths from 
the submersible surveys with all 
lengths from the trawl surveys, as 
well as in comparisons of lengths 
from the submersible surveys and 
trawl surveys over trawlable habi¬ 
tat. For 3 species, length distribu¬ 
tions were significantly different 
in comparisons of lengths obtained 
from submersible surveys on traw¬ 
lable and on untrawlable habitats. 
Trawl selectivity curves from recent 
stock assessments were evaluated 
in relation to the length data for 
greenspotted, greenstriped, and ca¬ 
nary rockfish. Although derived from 
a larger spatiotemporal extent than 
our study, greenspotted and green- 
striped rockfish selectivity curves 
appear to account for the reduced 
frequency of small fish in the trawl 
survey, whereas the canary rockfish 
selectivity curve does not. Similar 
comparisons between submersible 
and trawl-survey rockfish lengths 
from other regions of the west coast 
could help address spatial variabil¬ 
ity in trawl survey selectivity and 
further inform selectivity functions 
for stock assessments. 
Manuscript submitted 24 January 2018. 
Manuscript accepted 9 July 2018. 
Fish. Bull. 116: 291-301 (2018). 
Online publication date: 31 July 2018. 
doi: 10.7755/FB.116.3-4.7 
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. 
Diana L. Watters (contact author) 
E. J. Dick 
Southwest Fisheries Science Center 
National Marine Fisheries Service, NOAA 
110 McAllister Way 
Santa Cruz, California 95060 
Rockfishes (genus Sebastes) have 
been historically significant for Cali¬ 
fornia commercial and recreational 
fisheries. Approximately 40 of the 
more than 60 species that occur off 
California have been harvested over 
the last 150 years (Love et al., 2002; 
Love, 2006). Most of these species 
occur at depths of 30-500 m on the 
continental shelf and upper conti¬ 
nental slope off California, and as¬ 
sociate with complex rocky seafloor 
habitats, such as pinnacles, rock 
ridges, boulders, canyon walls, and 
cobbles, mixed with varying amounts 
of low relief soft sediments (Love and 
Yoklavich, 2006). The diversity of 
deepwater rockfishes and the com¬ 
plex habitats that they occupy make 
them difficult to study and manage. 
Most Pacific rockfishes are man¬ 
aged by the Pacific Fisheries Man¬ 
agement Council in accordance with 
its Pacific Coast Groundfish Fishery 
Management Plan and stock assess¬ 
ment process (website), as first re¬ 
quired by the Magnuson-Stevens 
Fishery Conservation and Manage¬ 
ment Act of 1976. Since 1999, several 
rockfish species have recovered from 
an overfished to a rebuilt status; 
currently, 2 species remain classified 
as overfished and in rebuilding sta¬ 
tus (cowcod [S. levis]] and yelloweye 
rockfish [S. ruberrimusj). However, 
regulatory measures implemented to 
reduce fishing mortality for rebuild¬ 
ing rockfish stocks have also reduced 
the amount of fishery-dependent 
data available for stock assessments 
(Field et al., 2006; Starr et al., 
2016). A principal source of fishery- 
independent data for rockfish stock 
assessments is the Northwest Fish¬ 
eries Science Center (NWFSC) West 
Coast Bottom Trawl Survey (hereaf¬ 
ter referred to as the trawl survey; 
Keller et al., 2017), which cannot 
be conducted in complex rocky habi¬ 
tats where the highest densities of 
most deep-water rockfishes occur. 
Recognizing that trawl survey data 
may not represent many rockfish 
populations adequately, the Pacific 
Fisheries Management Council has 
encouraged the development of sur¬ 
vey methods in untrawlable areas 
and research on the relative density, 
age, and length composition of rock¬ 
fishes in trawlable and untrawlable 
areas (PFMC 1 ). In particular, com¬ 
parisons of length composition data 
between trawlable and untrawlable 
1 PFMC (Pacific Fishery Management 
Council). 2013. Groundfish fishery 
management plan. In Research and 
data needs 2013, p. 21-31. Pacific Fish¬ 
ery Management Council, Portland, OR.. 
[Available at website.] 
