Fisheries and Resources Monitoring System

Witch flounder - Southern Grand Bank
Fact Sheet Title  Fact Sheet
Stocks management recommendations 2022
Witch flounder - Southern Grand Bank
Fact Sheet Citation  
Witch flounder in Div. 3NO
Owned byNorthwest Atlantic Fisheries Organization (NAFO) – ownership
ident Blockident Blockdisplay tree map
Species List:
Species Ref: en - Witch flounder, fr - Plie cynoglosse, es - Mendo, ru - Камбала длинная (красная) атлантическая
ident Block Witch flounder - Southern Grand Bank
Aq Res
Biological Stock: Yes         Value: Regional
Management unit: Yes        Reference year: 2021
Aq Res State Trend
Aq Res State Trend
Aq Res State Trend Aq Res State Trend
Aq Res State TrendNone-Low Fishing MortalityNo or low fishing mortalityGreen
Aq Res State TrendSmall stock sizeLow abundance

The stock has increased slightly since 2015 and is estimated at 49% BMSY .At the beginning of 2022, there is 9% risk of the stock being below Blim and less than 1% risk of F being above Flim. Recruitment is uncertain.
Habitat Bio
Climatic Zone: Temperate.   Bottom Type: Unspecified.   Depth Zone: Slope - Deepslope (500 m - 1000 m).   Horizontal Dist: Neritic.   Vertical Dist: Demersal/Benthic.  

Geo Dist
Geo Dist: Straddling between High Seas and EEZ

Water Area Overview
Spatial Scale: Regional

Water Area Overview
Aq Res Struct
Biological Stock: Yes

The fishery was reopened to directed fishing in 2015 and is exploited by otter trawl. Prior to the reopening, witch flounder were caught as bycatch in bottom otter trawl fisheries for yellowtail flounder, redfish, skate and Greenland halibut.

Recent catch estimates and TACs are:

Effects of the fishery on the ecosystem

No specific information available. General impacts of bottom trawl gear on the ecosystem should be considered.

Bio Assess
Ref Point

Reference points are estimated from the surplus production model. Scientific Council considers that 30% BMSY is a suitable biomass limit reference point (Blim) and FMSY a suitable fishing mortality limit reference point for stocks where a production model is used.

Projections and risk analyses

The probability of F exceeding Flim in 2022 is 14% at a catch of 1 175 t (TAC 2022). The probability of F being above Flim ranged from 1% to 50% for the catch scenarios tested. The population is projected to grow under all scenarios and the probability that the biomass in 2025 is greater than the biomass in 2022 is greater than 60% in all scenarios. The population is projected to remain below BMSY through to the beginning of 2025 for all levels of F examined with a probability of 86% or greater. The probability of projected biomass being below Blim by 2025 was 5% to 9% in all catch scenarios examined and was 4% by 2025 in the F=0 scenario.

Projected yield (t) and the risk of F> Flim, B< Blim and B< BMSY and probability of stock growth (B2025>B2022) under projected F values of F=0, F2021, 2/3 FMSY, 85% FMSY, and FMSY, and catch=TAC (1 175 t) are presented in the following tables.
Assess Models
Analytical assessment

This stock is assessed utilizing a surplus production model in a Bayesian framework. Full assessments were conducted annually from 2017-2020 and in 2022.

The input data were catch from 1960-2021, Canadian spring survey series from 1984-1990, Canadian spring survey series from 1991-2019 (no 2006, 2020 or 2021 surveys) and the Canadian autumn survey series from 1990-2020 (no 2014 or 2021 surveys).

The next assessment is planned for 2024.

Human impact

Mainly fishery related mortality. Other potential sources (e.g. pollution, shipping, and oil-industry) are undocumented. The impact of bottom fishing activities on major VMEs in the NRA was last assessed in 2021. The risk of Significant Adverse Impacts (SAIs) on sponge and large gorgonian VMEs was assessed to be low, while this risk for sea pen VMEs has been assessed as intermediate. The risks of SAIs on small gorgonian, black coral, bryozoan and sea squirt VMEs were assessed as high. This assessment of impacts of bottom fishing activities on VMEs does not include waters within coastal states jurisdictions. Within the Grand Bank (3LNO) EPU areas in Div. 3O and 3L have been closed to fishing to protect corals.

Biological and environmental interactions

Witch flounder in NAFO Divs. 3NO are distributed mainly along the tail and southwestern slopes of the Grand Bank.

The Grand Bank (3LNO) EPU continues to experience low overall productivity conditions, and total biomass remains well below pre-collapse levels. However, recent warming, earlier phytoplankton spring bloom, and an increase in the proportion of energy-rich copepod species may have positive effects on total ecosystem production in the coming years.

Fishing Mortality


Sci Advice

Special comments

It is unclear if the recruitment index (survey number of fish<21 cm) is representative. In the absence of Canadian surveys for 2021, current recruitment cannot be determined.
Management unit: Yes


Recommendation for 2023 and 2024

In the projection period there is less than a 10% probability of being below Blim, however the probability of exceeding Flim is estimated to be above 30% in 2024 for F greater than 2/3FMSY. Scientific Council therefore recommends that F should be no higher than 2/3 FMSY.

The Commission adopted a total allowable catch (TAC) of 1 175 t for 2021 and 2022. Convention General Principles are applied (NAFO GC Doc. 07-04).

The management unit is NAFO Divisions 3NO. The stock mainly occurs in Div. 3O along the southwestern slopes of the Grand Bank. In most years the distribution is concentrated toward the slopes but in certain years, a higher percentage may be distributed in shallower water.
Northwest Atlantic Fisheries Organization (NAFO) Scientific Council Documents SCR Docs. 22/005, 22/007, 22/014 and SCS Docs. 22/06, 22/09, 22/10, 22/13. Click to open
Northwest Atlantic Fisheries Organization (NAFO). 2022. Report of the Scientific Council Meeting, 03 – 16 June, 2022. NAFO SCS Doc. 22/18. Click to open
Northwest Atlantic Fisheries Organization (NAFO). 2008. Resolution on the Interpretation and Implementation of the Convention on the Future Multilateral Cooperation in the Northwest Atlantic Fisheries. 30th Annual Meeting, September 2008. NAFO/GC Doc. 08/3. Click to open
Northwest Atlantic Fisheries Organization (NAFO). 2007. Amendment to the Convention on Future Multilateral Cooperation in the Northwest Atlantic Fisheries. NAFO/GC Doc. 07/4. Click to open
powered by FIGIS  © FAO, 2024
Powered by FIGIS