2008-2009 Field Season Report Chapter 9 Antarctic Marine Living Resources Program NOAA-TM-NMFS-SWFSC-445 Demersal Finfi sh Survey of the South Orkney Islands Christopher Jones, Malte Damerau, Kim Deitrich, Ryan Driscoll, Karl-Hermann Kock, Kristen Kuhn, Jon Moore, Tina Morgan, Tom Near, Jillian Pennington, and Susanne Schöling Abstract A random, depth-stratifi ed bottom trawl survey of the South Orkney Islands (CCAMLR Subarea 48.2) fi nfi sh populations was completed as part of Leg II of the 2008/09 AMLR Survey. Data collection included abundance, spatial distribution, species and size composition, demographic structure and diet composition of fi nfi sh species within the 500 m isobath of the South Orkney Islands. Additional slope stations were sampled off the shelf of the South Orkney Islands and in the northern Antarctic Peninsula region (Subarea 48.1). During the 2008/09 AMLR Survey: • Seventy-fi ve stations were completed on the South Orkney Island shelf and slope area (63-764 m); • Th ree stations were completed on the northern Antarctic Peninsula slope (623-759 m); • A total of 7,693 kg (31,844 individuals) was processed from 65 fi nfi sh species; • Spatial distribution of standardized fi nfi sh densities demonstrated substantial contrast across the South Orkney Islands shelf area; • Th e highest densities of pooled fi nfi sh biomass occurred on the northwest shelf of the South Orkney Islands, at sta- tions north of Inaccessible and Coronation Islands, and the highest mean densities occurred within the 150-250 m depth stratum; • Th e greatest species diversity of fi nfi sh occurred at deeper stations on the southern shelf region; • Additional data collection of environmental and ecological features of the South Orkney Islands was conducted in order to further investigate Antarctic fi nfi sh in an ecosystem context. Introduction To characterize finfish stock biomass and biologi- Commercial exploitation of finfish in the South cal characteristics and determine whether shelf areas Orkney Islands (CCAMLR Statistical Subarea 48.2) oc- can be re-opened to possible finfish exploitation, a cured between 1977/78 and 1989/90. The main re- random, depth-stratified bottom trawl survey of the ported species captured in the region during this time South Orkney Islands was undertaken during Leg II period were Champsocephalus gunnari, Gobionotothen of the 2008/09 AMLR Survey. This survey represents gibberifrons and Notothenia rossii (CCAMLR, 1990a; the first comprehensive scientific characterization of 1990b). Other reported finfish species included Lepi- demersal fish along the fishable and accessible shelf re- donotothen squamifrons, Pseudochaenichthys georgia- gions of the South Orkney Islands since the 1998/99 nus, Chaenocephalus aceratus, Dissostichus eleginoides AMLR Survey. and unspecified finfish species. The first year of fish- The survey objectives included data collection to ing yielded a reported catch of almost 140,000 metric be used for estimates of biomass, distribution, species tons of C. gunnari, supported mainly by 1973/74 and and size composition, demographic structure, and diet 1974/75 cohorts (Kock and Jones, 2005). Both cohorts composition of finfish species, primarily within the were largely exhausted within two years, and overall 500 m isobath of the South Orkney Islands. A num- catches declined by almost two orders of magnitude ber of additional hauls were taken on slope areas (600- within a few years. Catches increased slightly in the 800 m) of both the South Orkney Islands and northern mid-1980s, primarily as a result of the 1980/81 cohort, Antarctic Peninsula regions. Several other sampling and decreased substantially once that cohort was ex- efforts and biological experiments were conducted hausted (Jones et al. 2000). The rapid declines of catch during the course of this survey, including buoyancy size and catch rate led CCAMLR, in 1990/91, to impose measurements, DNA collections, otolith sampling for a moratorium on all directed fishing for finfish in the age and growth studies, and other specimen/tissue col- South Orkney Islands (CCAMLR CM73/XVII). At pres- lections for biological, physiological, and phylogenetic ent, this moratorium remains in effect (CCAMLR CM studies. Other components of the South Orkney Is- 32-03). land shelf ecosystem examined during Leg II included Antarctic Ecosystem Research Dvision National Oceanic and Atmospheric Administration 49 Jones et al. 2009 Chapter 9 the physical oceanography (Chapter 1), krill density measure the trawl mouth dimensions in real time while and distribution (Chapter 12), benthic invertebrate sampling the station. megafauna (Chapter 10), and underwater camera/ Trawling operations were conducted aboard the video deployments (Chapter 11). The overall goals of R/V Yuzhmorgeologiya on 9 February 2009 through 9 Leg II were to collect information to be used toward an March 2009 (Table 9.1). There were a total of 75 hauls ecosystem-based assessment of the biomass and spa- completed on the South Orkney Island shelf and slope tial distribution of demersal fish in the South Orkney area, and three hauls taken off the northern Antarctic Islands; to characterize feeding patterns; and to exam- Peninsula slope area (Figure 9.1). The sampling strat- ine relationships between benthic and pelagic compo- egy for the South Orkney Islands survey was based on nents of the Antarctic ecosystem and their influence a random, depth-stratified survey design, and stations on demersal finfish. were positioned to account for as wide a geographic range as time, sea, and ice conditions permitted. Esti- Methods mates of seabed areas and bathymetric features were Bottom Trawling taken from Jones (2000). In all cases, a haul was taken The at-sea protocols used to conduct the bottom only after initial acoustic reconnaissance verified that trawl survey were based on those used during the bottom conditions were suitable for trawling. All final 1998/99 AMLR Survey of the South Orkney Islands decisions regarding sampling operations during the (Jones et al. 1999), with some modifications to include survey were made by the chief scientist in consultation additional research activities. A hard-bottom snapper with the fishing master and ship captain. trawl with vented V-Doors (Net Systems, Inc. Bain- In the South Orkney Islands there were three tar- bridge Island, WA) was used. The trawl was deployed geted designated depth strata: 50-150 m, 150-250 m, using a 6’6” wide by 12’7” diameter net reel, an 11’9” and 250-500 m; a limited number of hauls were tak- long by 12” diameter stern roller, two trawl winches, en in an additional depth stratum (on the slope) be- instrumented trawl blocks, and a third wire slip ring tween 600-800 m. These hauls were included on an winch. The headrope transducer platform of the trawl exploratory basis to increase collections of rare deep was instrumented with a Simrad FS25 trawl sonar sys- sea notothenioid species for ecological, taxonomic and tem to monitor the geometry of the mouth of the trawl physiological studies, as well as characterize benthic as it was deployed, record contact with the bottom, and invertebrate megafauna. The numbers of hauls within 68 6 9 4 3 10 12 60.4 2 1 7 13 89 87 5 11 69 85 15 78 97 19 60.6 67 64 75 62 63 82 81 60 79 28 20 76 98 60.8 57 16 83 96 23 22 61 59 55 58 54 51 30 29 49 48 40 61.0 88 50 31 21 26 32 33 27 24 34 45 41 61.2 95 Figure 9.1. Sta- tion locations, Latitude 61.4 46 by depth strata, 36 37 from Leg II of the 35 93 39 2008/09 AMLR 61.6 Survey, in the 43 73 South Orkney 44 103 42 Islands. Figure 61.8 94 Depth Strata 101 inset shows the 50-150 m 104 three trawls taken 62.0 150-250 m Joinville Is. on the slope of 250-500 m 600-800 m the northern Ant- 62.2 arctic Peninsula. 47.5 47.0 46.5 46.0 45.5 45.0 44.5 44.0 43.5 43.0 42.5 Longitude Antarctic Ecosystem Research Division 50 National Oceanic and Atmospheric Administration 2009 Chapter 9 Table 9.1. Station and fi nfi sh catch information for the 2008/09 AMLR Survey bottom trawl in the South Orkney Islands and along the northern Antarctic Peninsula slope. Number Total Number Total Station Latitude Longittude Avg. Finfi sh Latitude Longittude Avg. Finfi sh Date Finfi sh Number Station Date Finfi sh Number No. (S) (W) Depth Catch (Kg) (S) (W) Depth Catch (Kg) Species Finfi sh Species Finfi sh 4 9-Feb-09 60º25.77 46º26.16 142 9 81.42 239 43 21-Feb-09 61º43.41 45º50.04 398 9 42.33 189 3 10-Feb-09 60º26.00 46º18.66 142 11 236.23 790 42 21-Feb-09 61º49.47 46º12.52 453 10 16.84 102 9 10-Feb-09 60º25.00 45º56.34 228 10 588.80 1433 94 21-Feb-09 61º51.73 46º45.25 750 20 20.25 135 10 10-Feb-09 60º26.41 45º39.87 237 9 378.66 830 93 21-Feb-09 61º35.67 47º01.52 629 16 14.58 56 11 11-Feb-09 60º30.48 45º19.29 240 10 222.91 659 46 22-Feb-09 61º25.27 46º09.97 352 14 97.88 272 13 11-Feb-09 60º28.89 45º07.68 350 13 149.62 442 45 22-Feb-09 61º13.62 46º23.79 274 12 70.07 199 12 11-Feb-09 60º26.52 45º17.91 497 11 33.59 225 41 22-Feb-09 61º12.59 45º56.41 240 15 86.22 245 78 11-Feb-09 60º35.94 45º09.01 98 9 46.17 179 48 23-Feb-09 60º57.09 45º19.74 236 11 50.33 182 85 12-Feb-09 60º32.69 44º58.36 371 13 120.09 398 81 23-Feb-09 60º43.03 45º33.40 63 5 8.49 108 15 12-Feb-09 60º31.82 44º44.39 310 11 183.96 340 98 24-Feb-09 60º47.97 45º54.57 126 9 13.07 111 97 12-Feb-09 60º35.72 44º45.66 118 11 87.03 180 82 24-Feb-09 60º42.72 46º01.02 96 7 24.38 188 89 12-Feb-09 60º29.67 44º37.86 798 14 5.26 71 57 25-Feb-09 60º49.26 46º08.33 195 8 127.05 524 19 13-Feb-09 60º36.21 44º19.67 211 12 42.76 183 60 25-Feb-09 60º45.98