K.J. Hedges (Fisheries and Oceans Canada) Greenland halibut caught during 2025 trawl survey in NAFO Subarea 0A-0B; 0B biomass larger, 0A smaller
Report on Greenland halibut (Reinhardtius hippoglossoides) caught during the 2025 trawl survey in Subarea 0
Serial No. N7740
NAFO SCR Doc. 26/021
SCIENTIFIC COUNCIL MEETING –JUNE 2026
Northwest Atlantic Fisheries Organization
www.nafo.int Report on Greenland halibut (Reinhardtius hippoglossoides) caught during the 2025 trawl survey in Subarea 0 K.J. Hedges1 1Fisheries and Oceans Canada, Freshwater Institute, 501 University Cres., Winnipeg, Manitoba, Canada R3T 2N6
2026-06-08 Hedges, K.J. 2026. Report on Greenland halibut (Reinhardtius hippoglossoides) caught during the 2025 trawl survey in Subarea 0. NAFO Scientific Council Research Document, SCR Doc. 26/021: 1-51. Abstract A stratified-random otter trawl survey was conducted in Divisions 0A and 0B in fall 2025. The survey took place from October 19 to November 20, 2025. A Bacalao trawl was used with the R.V. Tarajoq. Survey stations were randomly located within depth strata in Divs. 0A and 0B. Near-bottom temperatures were similar to previous surveys varying between -0.81 to 1.57∘C in Div. 0A and -0.33 to 4.16∘C in Div. 0B. The highest mean temperature was in the 601-800 m stratum and the coldest mean was in the 201-400 m stratum in Div. 0A, and the highest mean temperature was in the 801-1000 m stratum and the coldest mean was in the 201-400 m stratum in Div. 0B. Greenland halibut were distributed throughout the survey area. A majority of both females (94.34%) and males (88.7%) were immature in Division 0A, but the ratios were more balanced in 0B, where 48.65% and 35.74% of females and males, respectively, were immature. The 2025 biomass estimates for 0A and 0B were 8.59e+04 t (S.E. 1.21e+04) and 2.12e+05 t (S.E. 6.32e+04), respectively. The 2025 abundance estimates for 0A and 0B were 1.19e+08 (S.E. 1.90e+07) and 1.51e+08 (S.E. 3.25e+07), respectively. These biomass and abundance values cannot be compared directly with the 1999-2017 time series from the R.V. Pâmiut because a calibration is not available to account for the changes in vessel and gear, and revisions to survey strata that were applied in 2022. Introduction A depth-stratified random multi-species bottom trawl survey was conducted in southern Division 0A (0A- South; to approximately 72.5∘N) and Div. 0B in Northwest Atlantic Fisheries Organization Subarea 0 using the R.V. Tarajoq during October 19 to November 20, 2025. Surveys during 2022-2025 used a Bacalao trawl; previous surveys during 1999-2019 used an Alfredo III trawl with the R.V. Pâmiut (1999-2017) and F.V. Helga Maria (2019). The survey stratification was altered in 2022 by adding a 201-400 m depth stratum to the existing strata (401-600, 601-800, 801-1000, 1001-1200, 1201-1400, 1401-1500 m). With the changes in vessel, gear, and stratification in 2022, without calibration experiments, data from 2022-2025 represent a new time series from the data collected during 1999-2019.
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www.nafo.int Deep-water surveys in 0A-South started in 1999 and were completed every second year between 2004 and 2014, then annually between 2015 and 2017. Surveys in 0B were less frequent, occurring in 2000, 2001, 2011 and 2013 to 2016. These surveys were all completed using the R.V. Pâmiut. Following retirement of the R.V.Pâmiut in 2018 the F.V. Helga Maria was used to conduct a survey of 0A-south in 2019, but post-survey analysis identified significant differences in trawl performance below 700 m, therefore the data were not accepted for assessing the status of the NAFO Subarea 0 stock. In 2022, surveys in 0A-south and 0B resumed using the R.V. Tarajoq (Table 1). Detailed descriptions of changes in survey coverage, timing, vessel and gear are provided in HEDGES (2023). The survey objectives are to: 1) Collect data required to establish age structure and estimate the population abundance, biomass, and recruitment of Greenland halibut; 2) Record numbers caught and collect length and weight data on all other commercial species to support by-catch monitoring through the calculation of abundance and biomass indices, and size structure of individual species; 3) Record numbers and collect weight data on all non-commercial species caught to allow calculation of abundance and biomass indices for individual species; 4) Collect additional data and biological samples as desired and as time permits (e.g. lengths for by-catch, maturity information, coral samples, other special requests); 5) Calculate total biomass caught per tow and per survey as an index of overall ecosystem productivity; 6) Collect temperature data at each fishing station. Table 1. Survey locations, dates, vessels and gear used since 1999 in NAFO Subarea 0. Year 0A-North 0A-South 0B Vessel Gear Accepted 1999
X
R.V. Pâmiut Alfredo III Y 2000
X R.V. Pâmiut Alfredo III Y 2001
X X R.V. Pâmiut Alfredo III Y 2002
2003
2004 X X
R.V. Pâmiut Alfredo III Y 2005
2006
X
R.V. Pâmiut Alfredo III Y 2007
2008
X
R.V. Pâmiut Alfredo III Y 2009
2010 X X
R.V. Pâmiut Alfredo III Y 2011
X R.V. Pâmiut Alfredo III Y 2012 X X
R.V. Pâmiut Alfredo III Y 2013
X R.V. Pâmiut Alfredo III Y 2014
X X R.V. Pâmiut Alfredo III Y 2015
X X R.V. Pâmiut Alfredo III Y
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www.nafo.int Year 0A-North 0A-South 0B Vessel Gear Accepted 2016
X X R.V. Pâmiut Alfredo III Y 2017
X
R.V. Pâmiut Alfredo III Y 2018
2019
X
F.V. Helga Maria Alfredo III N 2020
2021
2022
X X R.V. Tarajoq
Y 2023
X X R.V. Tarajoq
Y 2024
X X R.V. Tarajoq
Y 2025
X X R.V. Tarajoq
Y Methods Stratification and Set Selection A depth stratification scheme similar to that used by the Greenland Institute of Natural Resources for the Division 1CD survey was developed in 2008 to facilitate comparisons between surveys conducted in Canadian and Greenland waters. The depth bins were redefined in 2022 using updated bathymetric data, resulting in slight differences from the depth bins used in surveys conducted between 1999 and 2019. Therefore, sets completed during 1999-2019 were re-assigned to the new depth strata post-hoc to allow consistent spatial extrapolation when calculating abundance and biomass indices across years (Figures 1, 2 and 3, and Table 2). Previous revisions to the survey strata and changes to earlier index calculations are described in TREBLE (2020).
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Figure 1. Map of NAFO areas and survey strata.
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Figure 2. Stratification scheme for Division 0A-South.
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Figure 3. Stratification scheme for Division 0B.
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www.nafo.int Table 2. Survey stratification scheme for NAFO Subarea 0. Survey Area Stratum Depth Stratum (m) Area (km2) Assigned Sets (1/750 km2) 0A A1-3 201-400 2,441.00 2 0A A1-4 401-600 2,151.56 5 0A A1-5 601-800 794.75 5 0A A1-6 801-1000 603.81 5 0A A1-7 1001-1200 745.21 5 0A A1-8 1201-1400 812.76 2 0A A2-3 201-400 5,095.00 2 0A A2-4 401-600 4,649.39 4 0A A2-5 601-800 2,250.41 2 0A A2-6 801-1000 1,144.81 2 0A A2-7 1001-1200 1,873.10 3 0A A2-8 1201-1400 2,151.49 3 0A A2-9 1401-1500 1,153.19 2 0A A3-3 201-400 1,950.00 2 0A A3-4 401-600 784.79 2 0A A3-5 601-800 759.93 2 0A A3-6 801-1000 1,020.40 2 0A A3-7 1001-1200 1,306.99 2 0A A3-8 1201-1400 1,145.95 2 0A A4-3 201-400 3,926.00 2 0A A4-4 401-600 1,921.58 2 0A A4-5 601-800 2,483.22 3 0A A4-6 801-1000 1,375.61 3 0A A4-7 1001-1200 1,635.65 2 0A A4-8 1201-1400 1,071.88 2 0B B1-1000 1001-1200 6,585.63 7 0B B1-1200 1201-1400 4,753.85 6 0B B1-1400 1401-1500 1,964.57 2 0B B1-200 201-400 11,285.00 16 0B B1-400 401-600 17,396.93 16 0A B1-600 601-800 2,282.96 2 0B B1-600 601-800 2,282.96 8 0B B1-800 801-1000 8,053.13 10 0B B2-200 201-400 25,879.00 24 The survey area between 200 and 1500 m in Div. 0A-South (to approximately 72∘N) is 47,924 km2 (Table 1) within which 79 sets are randomly assigned to 28 sub-strata (4 sub-stratum in each of 7 depth strata). In Div. 0B, 110 survey stations are divided among 8 sub-strata (2 sub-strata within the 201-400 m depth stratum; all other depth strata are not subdivided). Set selection is based on a coverage level of approximately 1 set per 750 km2. A minimum of two sets are randomly selected from numbered units within each sub-stratum using a
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www.nafo.int buffered random design (KINGSLEY (2004)). If a set cannot be fished due to bad bottom, ice, etc. then the tow is taken in an adjacent unit as close to the missed site within the sub-stratum as feasible given the conditions. When this is not possible the tow may be re-located to an area of the sub-stratum where there are “holes” in the set coverage and a unit location selected at random from those available in that area. Vessel and Gear The surveys prior to 2019 were conducted by the RV Pâmiut, a 1084 GRT stern trawler measuring 53 m in length. An Alfredo III bottom otter trawl with rock hopper ground gear was used. Mesh size was 140 mm with a 30 mm mesh liner in the cod end. Trawl doors were Injector International, measuring 7.5 m2 and weighing 2800 kg. These doors replaced the Greenland Perfect doors (9.25 m2 and 2420 kg) in 2004. The average net height was 20 cm higher with the new doors but the overall net performance was not significantly different (95% level) (Jørgensen personal communication). More information about the trawl and gear can be found in JØRGENSEN (1998). A Furuno based system mounted on the head rope measured net height and was used to determine bottom contact and the start/finish of each tow. Scanmar sensors measured the distance between the trawl doors and since 2010 the wingspread. The 2019 survey vessel, FV Helga Maria, was 1470 GRT and 57 m in length. The trawl gear and rigging as described above remained unchanged. The warps, bridle, ground gear and distance from the hanging blocks were kept the same as on the RV Pâmiut. The fishing procedures were also the same, the RV Pâmiut captain and crew were involved prior to and during the survey. See Novaczek WHEELAND L. J. and Nogueira (2020) for additional information on vessel comparison and gear performance. Since 2022 the survey has been conducted using the RV Tarajoq, which is a 2841 GRT and 61.4 m long stern trawler. The RV Tarajoq used a Bacalao trawl but followed the same fishing procedures as the RV Pâmiut and had the same captain and crew. Oceanographic Sampling A Seabird 19 CTD (conductivity, temperature and depth recorder) was mounted on the head-rope beginning in 2010 and was used to determine temperature, depth and time spent on the bottom. In the few cases where there were no data from the CTD, data from the Furuno trawl eye sensor was used to determine bottom temperature. Two oceanographic lines that cross the shelf and slope at Broughton Island (near 68∘N) and Cape Christian (near 71∘N) were included in survey plans prior to 2022. These transect lines were completed when conditions (time and ice) allowed. The transect lines were removed from the survey design in 2022 because they had not been completed in most years. The trawl mounted CTD continues to provide temperature and salinity data at the trawl mouth to associate environmental conditions with trawl catches. In addition, in 2017 an annual ecosystem-foc