Download CO # 47: Ensure that Greenland halibut > 40 cm (influential predator

Greenland halibut > 40 cm (influential predator) within the PBGB LOMA
Potentially Harmful Activity (X)
Potentially Harmful Stressor (X)
Bottom trawl
Oil pollution
X
Fishing
Other
harvest
Seabed
alteration
Coastal
alteration
Disturbance
Marine
pollution
Industrial effluent
Fishplant effluent
Sewage
Historic military waste
Long range transport of nutrients
Acid rain
Persistent Organic Pollutants
(Eutrophication
)
Ghost nets
Litter
Other contaminants (specify)
Ice distribution
Otter trapping
Seal hunt
Seabird hunt
Seaweed harvest
Anchor drops/drags
Ore spill
Fish offal dumping
Finfish aquaculture
Dredge spoil dumping
Dredging
Climate
Change
Temperature change
Sea-level rise
Ocean acidification
Current shifts
Increased storm events
Increased UV light
Oxygen depletion
Changes in freshwater runoff
Other (specify)
Green crab
Mining/Oil & gas drilling
Cables
Freshwater diversion
Subtidal construction
Intertidal/coastal
construction
Harmful
species
Membranipora
Golden Star Tunicate
Violet Tunicate
Vase Tunicate
Codium fragile
Clubbed Tunicate
Didemnum
Harmful Algal Blooms
Disease organisms (human waste)
Disease organisms (aquaculture)
Other (specify)
Scallop dredges
Clam dredges
Midwater trawl
Gillnets (bottom)
Gillnets (pelagic)
Longline
Seine (pelagic)
Recreational cod fishery
Crab pots
Lobster pots
Whelk pots
Other (specify)
X
X
Other (specify)
Vessel traffic
Ship strikes
Ecotourism
Marine construction
Seismic surveys
Navy sonar
Other (specify)
Other
1
Background Information
Greenland halibut, also called turbot, is a deep-water, highly migratory groundfish species,
and is the most extensively distributed flatfish in the North Atlantic. Distribution is rather
continuous from Canadian waters in the western Atlantic to the Barents Sea in the Northeast
Arctic (Scott & Scott, 1988). In the Placentia Bay-Grand Banks area Greenland halibut are
concentrated mainly along the northeast edge of the Grand Bank and the slope of the
Northeast Newfoundland Shelf. However, distribution also extends into the Flemish Pass
area and along the southeast and southwest slopes of the Grand Bank, and continues into the
Laurentian Channel (Bowering & Chumakov, 1989; Bowering & Nedreaas, 2000).
In Newfoundland, Greenland halibut may reach a body length of 100-110 cm, and most
individuals larger than 90 cm are females (Fisheries and Oceans Canada, 2006c). Fecundity
increases with body length in Greenland halibut in Newfoundland (Bowering & Chumakov,
1989). In the Newfoundland-Labrador area, fecundity was in the range of 15,000-215,000
eggs per female, but there may be geographic variation in the fecundity of Greenland halibut
in the Newfoundland region (Scott & Scott, 1988).
Bottom trawl surveys conducted in eastern Newfoundland (NAFO Subarea 2 and Division 3)
during the late 1970’s indicated an increase in average body length of Greenland halibut with
increasing depth across the Labrador and northeast Newfoundland shelves (Bowering &
Chumakov, 1989). Highest catches of mature fish also occurred at greater depths and at more
northerly locations toward Davis Strait (Bowering & Nedreaas, 2000). These data suggest
that as Greenland halibut in eastern Newfoundland mature, they move to progressively
deeper waters and migrate northward to spawning grounds in Davis Strait (Bowering &
Chumakov, 1989; Bowering & Nedreaas, 2000; Templeman, 1973).
The reproductive biology of this stock is poorly understood. The main spawning area for this
stock is hypothesized to be in the Davis Strait, yet spawning Greenland halibut have also
been observed in the Flemish Pass. The eggs and larvae of Greenland cod are planktonic,
with as many as 160,000 propagules from a single fish. Eggs and larvae from spawning in the
Davis Straight can drift for many weeks before eventually turning southward where larvae
and juveniles develop and eventually drift with the current southward to the continental shelf
and Grand Banks (Templeman, 1973).
Greenland halibut spawn at great depths (600 to > 1,200 m) and the eggs and larvae have
been found at depths of 600-1,000 m in waters 680-1,660 m deep (Jorgensen, 1997). It is
hypothesized that several eggs and larvae are also moved southward by the Polar and
Labrador currents and are consequently led along the Labrador-Newfoundland continental
shelf and into the deepwater bays along the east coast of Newfoundland (Templeman, 1973).
Historically, larger juvenile Greenland halibut were plentiful in the deepwater bays off the
east coast of Newfoundland, an observation that has led to the hypothesis that larvae caught
in the current off Baffin Island tend to drift and colonize banks off Labrador and eastern
Newfoundland (Templeman, 1973).
2
Greenland halibut inhabiting coastal bays of Newfoundland and the Labrador-Newfoundland
Shelf are mostly immature (Bowering, 1983). Most mature fish are found in deeper waters of
the continental slope and farther to the north. Longline and gillnet surveys in White, Notre
Dame, Bonavista, and Trinity bays during the mid-1960’s indicated that the largest
concentrations of Greenland halibut were at depths of 274-594 m and near bottom
temperatures of 1-3C. These catches were dominated by juveniles, which is consistent with
the observation that older, larger Greenland halibut are captured in larger numbers farther
offshore and in deeper waters (Bowering, 1983; Bowering & Nedreaas, 2000).
Adult Greenland halibut have been shown to migrate between summer feeding grounds and
winter spawning areas on an annual basis (Jorgensen, 1997). There is evidence of similar
migrations in Newfoundland waters (Bowering & Nedreaas, 2000).
Average bottom trawl catches of Greenland halibut in the Northwest Atlantic generally
increase with depth, peak, and then decline. The highest catches appear to peak at greater
depths going northward. There is also a tendency for average fish size to increase with
increasing depth, which is evident in all areas investigated in the Northwest Atlantic.
Generally, larger fish become more abundant and smaller fish less abundant in progressively
deeper water, with peak abundance occurring over a depth range of 400-1,000 m. Although
there are no clear trends in distribution of Greenland halibut with respect to bottom water
temperatures, they are generally most abundant within a temperature range of 2-6C
(Bowering & Nedreaas, 2000).
Bowering and Parsons (1986) noted a decrease in the catch of mainly age 1 Greenland
halibut in bottom trawls in the Newfoundland region at night, which they attributed to a
vertical migration into the water column (Bowering & Parsons, 1986). Pelagic catches in the
Davis Strait area were in near-surface (50-300 m) waters to the bottom at depths of 4001,563 m. Greenland halibut in the pelagic catches ranged in length from 8-52 cm, while
bottom catches ranged from 22-100 cm (Jorgensen, 1997). Because the length distribution of
fish captured in the water column at night reflected the length distribution of fish captured on
the bottom during the day, Jorgensen (1997) suggested that the fish likely migrated into the
water column from great depths as opposed to movement from adjacent shallow waters
(Jorgensen, 1997).
The main prey items for Greenland halibut are size dependent and vary spatially. Smaller
Greenland halibut feed on small crustaceans, sea snails, squid, capelin and northern shrimp
while larger individuals prey mainly on juvenile Greenland halibut and redfish. Predators of
Greenland halibut include seals, Greenland sharks and cod (Scott & Scott, 1988).
Both spring and fall surveys identify a drop in abundance during the late 1980s and early
1990s with an increase after the introduction of the Campelen trawl (Fall 1995). The
exploitable biomass has been declining in recent years and is presently estimated to be at its
lowest observed level. In recent years recruitment has been below average and fishing
mortality has increased substantially (estimated as the highest in the time series) (Templeman
& Davis, 2006).
3
The commercial fishery for Greenland halibut in the Northwest Atlantic has been ongoing
since the mid 1800’s. It has been subjected to intensive fishing throughout the coastal waters
of Canada, Greenland, Iceland, Faroe Islands, Norway and Russia especially since the
1960’s. For management purposes, Greenland halibut are treated as three stocks in the
Northwest Atlantic: 1) Baffin Island-West Greenland (NAFO Subareas 0 and 1), 2)
Labrador-east Newfoundland (NAFO Subarea 2 + Div. 3KL), and 3) Gulf of St. Lawrence
(Fisheries and Oceans Canada, 2006b). With the decline in other groundfish stocks during
the 1990’s, Greenland halibut became the most significant groundfish fishery in the
Newfoundland region (Fisheries and Oceans Canada, 2001; Fisheries and Oceans Canada,
2006a; Fisheries and Oceans Canada, 2006c; Kulka, 2001; Templeman, 1973).
During the late 1980’s there was a shift in the distribution of Greenland halibut from the
eastern Newfoundland-Labrador area to the deep waters in the southern area of the Flemish
Pass (Bowering et al., 1993). High concentrations of Greenland halibut in the Flemish Pass
area resulted in the development of a large unregulated fishery in the early 1990’s. Fishing
pressure has been reduced in this area since 1995 and the geographic distribution patterns of
Greenland halibut in the eastern region of Newfoundland and Labrador appear to be
returning to those observed before the southward shift in distribution (Brodie et al., 1998).
The Greenland Halibut (turbot) fishery is focused offshore in areas along the continental
slope, with highest landings by the NL fleet from 3K. Total NL landings (2000-2003)
average 2,300 tonnes while Scotia-Fundy landings (2000-2003 averaged 45 tonnes/year).
Gillnet is the dominant gear, followed by otter trawl, with minimal longline catches, although
the highest landings are taken by otter trawl. Juvenile turbot are also taken in the Canadian
shrimp fishery.
Figure 1. Distribution of Greenland halibut (Brown et al., 2005).
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Figure 2. Distribution of Greenland halibut on spring research surveys from 1998-2000
(Kulka et al., 2003). Grey sections represent areas samples with no catch rate values.
Figure 3. Distribution of Greenland halibut on fall research surveys from 1998-2000 (Kulka
et al., 2003). Grey sections represent areas samples with no catch rate values.
Bottom trawl:
The main directed fisheries in NL using bottom trawl target yellowtail, redfish, turbot, skate
and shrimp. Based on logbook data from 2000 to 2003, average annual landings (directed
and by catch) of turbot using otter trawl was 1,530 tonnes (Fisheries and Oceans Canada,
5
2007). The Scotia-Fundy fleet 45 tonne shrimp trawls have a high by catch of juvenile
turbot, but do not perturb the < 40 cm class. Screened in.
Gillnet (bottom):
Gillnet mesh size is regulated to avoid catching undersized fish, and turbot under 40cm are
generally excluded from legal gillnets used in the offshore areas of the LOMA, and are not
considered a stressor to the CP. Screened out.
Longline:
Longline is used for a targeted Greenland Halibut fishery, but landings are minimal.
Screened out.
Key Activities/Stressors:
 Bottom trawl
6
Reference List
1. Bowering, W. R. (1983). Age, growth, and sexual maturity of Greenland halibut,
Reinhardtius hippoglossoides (Walbaum), in the Canadian Northwest Atlantic. Fish
Bulletin, 81, 599-611.
2. Bowering, W. R., Brodie, W. B., & Power, D. (1993). An evaluation of the status of the
Greenland halibut resource in NAFO Subarea 2 and Divisions 3KLM. (Rep. No. SCR
Doc. 93/75). Northwest Atlantic Fisheries Organization.
3. Bowering, W. R. & Chumakov, A. K. (1989). Distribution and relative abundance of
greenland Halibut (Reinhardtius hippoglossoides (Walbaum)) in the Canadian
Northwest Atlantic from Davis Strait to the northern Grand Bank. Fisheries Research,
7, 301-327.
4. Bowering, W. R. & Nedreaas, K. H. (2000). A comparison of Greenland halibut
(Reinhardtius hippoglossoides (Walbaum)) fisheries and distribution in the Northwest
and Northeast Atlantic. Sarsia, 85, 61-76.
5. Bowering, W. R. & Parsons, D. (1986). Diel Variability in Trawl Catches of Greenland
Halibut from the Channels off Coastal Labrador and Implications for Resource
Assessment. North American Journal of Fisheries Management, 6, 149-155.
6. Brodie, W. B., Bowering, W. R., Power, D., & Orr, D. (1998). An assessment of
Greenland halibut in NAFO Subarea 2 and Divisions 3KLMNO (Rep. No. SCR Doc.
98/47). NAFO.
7. Brown, S. K. R., Zwanenburg, K., & Branton, R. (2005). East Coast of North America
Strategic Assessment Project, Groundfish Atlas Bedford Institute of Oceanography,
Dartmouth, Nova Scotia: OBIS Canada.
8. Fisheries and Oceans Canada (2001). Atlantic Halibut on the Scotian Shelf and
Southern Grand Bank (Div. 4VWX3NOP) (Rep. No. A3-23 (2001)).
9. Fisheries and Oceans Canada (2006a). Atlantic Halibut on the Scotian Shelf and
Southern Grand Banks (Div. 3NOPs4VWX) (Rep. No. 2006/038). Canadian Science
Advisory Secretariat Science Advisory Report.
10. Fisheries and Oceans Canada (2006b). Integrated Fisheries Management Plan for
Capelin 2006-2008, NAFO Divisions 2J3KL, 3P and 4RST.
11. Fisheries and Oceans Canada. (6-6-2006c). Underwater World: Atlantic Halibut.
Ottawa, Ontario, Communications Directorate, Fisheries and Oceans Canada.
Ref Type: Pamphlet
12. Fisheries and Oceans Canada The Grand Banks of Newfoundland: Atlas of Human
Activities. The Grand Banks of Newfoundland: Atlas of Human Activities, (in press).
7
13. Jorgensen, O. A. (1997). Movement patterns of Greenland halibut (Reinhardtius
hippoglossoides (Walbaum)), at west Greenland, as inferred from trawl survey
distribution and size data. J.Northw.Atl.Fish.Sci., 21, 23-37.
14. Kulka, D. W. (2001). Distribution of Greenland Halibut and By-catch Species that
Overlap the 200-mile Limit Spatially and in Relation to Depth - Effect of Depth
Restrictions in the Fishery (Rep. No. NAFO SCR Doc. 01/40, Serial No. N4418).
Northwest Atlantic Fisheries Organization.
15. Kulka, D. W., Antle, N. C., & Simms, J. M. (2003). Spatial Analysis of 18 Demersal
Species in Relation to Petroleum License Areas on the Grand Banks (1980-2000) (Rep.
No. Canadian Technical Report of Fisheries and Aquatic Sciences 2473). Fisheries and
Oceans Canada.
16. Scott, W. B. & Scott, M. G. (1988). Atlantic Fishes of Canada. Canadian Bulletin of
Fisheries and Aquatic Sciences, 219.
17. Templeman, N. D. & Davis, M. B. (2006). Placentia Bay-Grand Banks Ecosystem
Overview and Assessment Report (DRAFT) Newfoundland & Labrador: Fisheries and
Oceans Canada.
18. Templeman, W. (1973). Distribution and abundance of the Greenland halibut,
Reinhardtius hippoglossoides (Walbaum), in the Northwest Atlantic. ICNAF Res.Bull,
10, 84-98.
8
Greenland halibut > 40 cm (influential predator) within the PBGB LOMA
Bottom trawl
Magnitude of Interaction
Areal extent:
 Greenland halibut are concentrated along the northeast edge of the Grand Bank and
the slope of the Northeast Newfoundland Shelf. The distribution also extends into the
Flemish Pass area and along the southeast and southwest slopes of the Grand Bank
and continuing into the Laurentian Channel (Kulka et al., 2003).
Figure 1. Distribution of Greenland halibut (Brown et al., 2005).
Figure 2. Distribution of Greenland halibut on spring research surveys from 1998-2000
(Kulka et al., 2003). Grey sections represent areas samples with no catch rate values.
Figure 3. Distribution of Greenland halibut on fall research surveys from 1998-2000
(Kulka et al., 2003). Grey sections represent areas samples with no catch rate values.




Greenland halibut greater than 40 cm are often caught in greater depths to 1600m
(Scott & Scott, 1988)
Canadian trawl survey data show that almost all, 99% for Canadian surveys, of the
Greenland halibut (> 70 cm) were distributed at depths greater than 800m (Kulka et
al., 2001).
Based on the Canadian fishery for Greenland halibut (2GHJ3KLNO) average size in
the catch was observed to increase with depth from about 35 cm to 52 cm at 1200+ m
for otter trawls. Percent of the catch < 70 cm for all gears was close to 100% at depths
shallower than 700m, decreasing to 96% for otter trawls and 65% for gillnets at 1200
m (Kulka et al., 2001).
Greenland halibut are found at depths in excess of 457 m, and their total depth range
is between 90-1600 m and within a temperature range of 0-4.5 oC (Scott & Scott,
1988).
Figure 4. Persistent areas of high intensity trawling in the Atlantic over the period 1980
2000. The second figure shows locations where >100% of the area was trawled in the
Atlantic in any year (centroids of areas where total area trawled exceeded extent of the
area) (Kulka & Pitcher, 2001).
Figure 5. Areal extent of bottom trawl use, Newfoundland Region fisheries, 1998 – 2007
(Fisheries and Oceans Canada, 2008)


Bottom trawling is concentrated above 800m depth within an area estimated at
281,600 km2 of the EBSA
Based on this information, the area of overlap for the CP and bottom trawl is
estimated to be 100%.
Score 10
Contact:
 In relation to bottom trawl, Quantitative Fishing Gear Scores (Fisheries and Oceans
Canada, 2007a) for “contact” are high (75-100%) for bony fish species.
 There is a directed fishery for Greenland halibut in the EBSA and it is a NAFO
managed stock (Fisheries and Oceans Canada, 2007b). Greenland halibut is also
caught as bycatch in other fisheries using otter trawl (redfish, and Northern shrimp)
(Fisheries and Oceans Canada, 2007b).
 Directed bottom trawl fisheries for Greenland halibut currently fish at greatly reduced
TAC compared to historical levels. Directed fisheries score 100%.
 Since Greenland halibut is targeted but catches are lower for larger fish, and bycatch
is moderate in relation to other fisheries, we have selected a score lower than that for
a directed fishery (10) but at the high end of the low range, 40%.
Score 4.0
Duration:
 In the Placentia Bay-Grand Banks area Greenland halibut are concentrated mainly
along the northeast edge of the Grand Bank and the slope of the Northeast
Newfoundland Shelf. However, distribution also extends into the Flemish Pass area
and along the southeast and southwest slopes of the Grand Bank, and continues into
the Laurentian Channel (Bowering & Chumakov, 1989; Bowering & Nedreaas,
2000).
 Greenland halibut are most prevalent from northern Labrador to the northern Grand
Bank with small numbers recorded in the vicinity of the Flemish Cap. Greenland
halibut are found incidentally on St. Pierre Bank with a small localized concentration
located in Fortune Bay (Bowering & Chumakov, 1989). Earlier investigations by
Templeman (1973) indicated that Greenland halibut were found in the northern Gulf
of St. Lawrence in relatively small numbers (Templeman, 1973). More investigations
have shown that Greenland halibut have become also commercially abundant in this
area with very little occurrence on the Scotian Shelf (Bowering & Chumakov, 1989).
 Bottom trawl is used within the LOMA throughout the year to harvest a range of
species including redfish, white hake, and Northern shrimp. NAFO vessels also trawl
outside the EEZ.
 There is evidence in Newfoundland that adult Greenland halibut have been shown to
migrate between summer feeding grounds and winter spawning areas on an annual
basis (Templeman, 1973).
 Spawning is thought to occur in the deep slope area of Davis Strait along the
boundary between Greenland and Canada at depths of 600-1000m spawning may also
take place in continental slope waters of similar depth and moderately warm waters
off eastern Labrador and perhaps as far south as the northern Grand Bank. Greenland
halibut also spawn in the southern Gulf of St. Lawrence, apparently in the area of the
southern Esquiman Channel and Laurentian Channel during the winter (Jorgensen,
1997)
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


Jorgensen (1997) concluded that spawning takes place in Davis Strait between midDecember and mid-April. Analysis of sexual maturity of female Greenland halibut
collected from the Flemish Pass identified two peak spawning periods, a main
spawning peak in the summer (July-August) and a secondary peak in December
(Jorgensen, 1997)
Based on these fishing seasons (Fisheries and Ocean Canada, 2005; Fisheries and
Ocean Canada, 2007; Fisheries and Ocean Canada, 2008), the activity of bottom
trawling occurs 12 months of the year, and the CP is present within the LOMA year
round.
Greenland halibut > 40 cm migrate to spawn and although there are some spawning
grounds within the LOMA, it is unknown which stocks migrate to which spawning
areas.
Bottom trawling occurs 100% of the time the LOMA is occupied by the CP
(Greenland halibut > 40 cm), 9 out of 12 months of the year.
Score 7.5
Intensity:
 Halpern et al. (2008) have developed maps showing the global intensity of several
anthropogenic stressors including demersal destructive fishing, which includes
bottom trawl fisheries (see map below). This map can be used to provide guidance in
scoring the intensity of a stressor in relation to maximum (100%) intensity in a global
context, in accordance with the scale provided below.
 This map shows a high intensity (80-100%) along the eastern slope of the northern
and southern Grand Banks, but lower levels on the Southwest Edge and Slope.
Halpern’s fishing maps are based on (1999-2003) data, and better represent NAFO
fisheries (which are notoriously variable year to year), than Canadian fisheries, and
are not as spatially precise on a local scale as long term local data.
Map colour
Red
Orange
Yellow
Light Blue
Dark Blue
Figure 6. Global Intensity of Bottom trawl, adapted from (Halpern et al., 2008)
Intensity
80-100%
60-80%
40-60%
20-40%
0-20%



Kulka and Pitcher (2001) studied the spatial extent of highly trawled areas in the
Grand Banks (see Figure 4 above). Some locations within the LOMA are shown as
being persistent areas of high intensity trawling (Kulka, 2006).
Bottom trawl is responsible for 32% of landings (shrimp and groundfish combined)
from 1998 – 2007 in the LOMA, for Newfoundland Region fisheries, with average
annual landings from Newfoundland Region fisheries (Fisheries and Oceans Canada,
2008) of 16,915t, followed by gillnet at 6,789t and longline landings of 1,532t.
Based on both global and local data, we have estimated an intensity of 90%.
Score 9
Magnitude of Interaction: (10 x 4 x 7.5 x 9)/1000 = 2.7
Sensitivity
Sensitivity of the CP to acute impacts:
 In relation to bottom trawl, Quantitative Fishing Gear Score (Fisheries and Oceans
Canada, 2007a) for “harm” are variable (1-100%) for bony fish species, depending on
the fishery, and without greater detail on the rationale behind the scores, they do not
provide particularly useful guidance.
 Bottom trawl was assigned an ecological rating of “high impact” (the highest of 5
categories) in relation to ground fish (Fuller et al., 2008).
 Trawling is a threat to Greenland halibut greater than 40 cm in the LOMA due to a
destructive nature of the fishery (Fisheries and Oceans Canada, 2006; Huse et al.,
1999; Kulka, 2001; Kulka et al., 2001; Scott & Scott, 1988). Within the LOMA,
Greenland halibut are taken as bycatch in redfish fisheries and Northern shrimp
fisheries (Fisheries and Oceans Canada, 2007b).
 We have therefore selected a score (4) within the moderate range
Score 4
Sensitivity of the CP to chronic impacts:
 Canadian catches increased from fairly low levels in the early 1960s to almost 32,000
tons in 1980 then declined steadily to between 2900 and 6300 tons in each year from
1993-99. This declining trend was mainly a result of low catch rates and reduced
effort, as fishers pursued other species such as snow crab which were more profitable.
In 2000, the Canadian catch in NAFO Subarea 2 and Divisions 3KLMNO increased
to about 10,600 tons, more than two and a half times the catches in 1998 and 1999.
However, catches declined by more than 2000 tons from 2000 to 2001, then declined
by a similar amount to about 6300 tons in 2002. Since then, catches have mainly been
around 6500 tons per year. Reasons for fluctuations in catch and effort include a
switch of some effort by fishers in Divs. 3KL between snow crab and Greenland
halibut due to changes in quotas and product prices, combined with variable catch
rates for Greenland halibut in some of the traditional fishing areas (Brodie et al.,
2007).



The directed Greenland halibut fishery, a NAFO managed stock since 1974,
fluctuates with price trends and total allowable catches, therefore chronic sensitivity
is in the moderate range (Fisheries and Oceans Canada, 2004).
Greenland halibut greater than 40 cm are at lower risk of continually being depleted
within the PBG LOMA since they are more commonly found at greater depths,
decreasing their risk to bottom trawls
Therefore, we have selected a score (5) within the moderate range.
Score 5
Sensitivity of ecosystem to harmful impacts to the CP:
 Greenland halibut greater than 40cm are at a risk of predation by larger fish such as
cod, salmon, and larger Greenland halibut (Scott & Scott, 1988). The Greenland shark
is also considered the most important predator of Greenland halibut (irrespective of
size) along with white whales, narwhals, and hooded seals (Scott & Scott, 1988).
 Larger Greenland halibut in deep water eat primarily capelin, which were the most
important food identified in the diet of Greenland halibut that were 20-80 cm in
length and smaller Greenland halibut were also an important prey particularly when
capelin were not available (Bowering, 1983; Bowering & Chumakov, 1989;
Bowering & Parsons, 1986; Scott & Scott, 1988; Templeman, 1973).
 There is little information on the importance of the Greenland halibut to the
ecosystem and therefore we have selected a score (3) within the low range.
Score 3
Sensitivity: (4 + 5 + 3)/3 = 4.0
Risk of Harm: MoI x S = 2.7 x 4 = 10.8
Certainty Checklist
Answer yes or no to all of the following questions. Record the number of NO’s to the 9
questions, and record certainty according to the scale provided below:
1
No’s = High certainty
2 - 3 No’s = Medium certainty
No’s = Low certainty
>4
Y/N
N Is the score supported by a large body of information?
Y Is the score supported by general expert agreement?
N Is the interaction well understood, without major information gaps/sources of error?
Y Is the current level of understanding based on empirical data rather than models,
anecdotal information or probable scenarios?
Y Is the score supported by data which is specific to the region, (EBSA, LOMA, NW
Atlantic)?
N Is the score supported by recent data or research (the last 10 years or less)?
Y
Is the score supported by long-term data sets (ten years or more) from multiple
surveys (5 years or more)?
Y Do you have a reasonable level of comfort in the scoring/conclusions?
Y Do you have a high level of confidence in the scoring/conclusions?
Certainty score: Medium
For interactions with Low certainty, underline the main factor(s) contributing to the
uncertainty:
Lack of comprehensive data
Lack of expert agreement
Predictions based of future scenarios which are difficult to predict
Other (provide explanation)
Suggest possible research to address uncertainty.
Reference List
1. Bowering, W. R. (1983). Age, growth, and sexual maturity of Greenland halibut,
Reinhardtius hippoglossoides (Walbaum), in the Canadian Northwest Atlantic. Fish
Bulletin, 81, 599-611.
2. Bowering, W. R. & Chumakov, A. K. (1989). Distribution and relative abundance
of greenland Halibut (Reinhardtius hippoglossoides (Walbaum)) in the Canadian
Northwest Atlantic from Davis Strait to the northern Grand Bank. Fisheries
Research, 7, 301-327.
3. Bowering, W. R. & Nedreaas, K. H. (2000). A comparison of Greenland halibut
(Reinhardtius hippoglossoides (Walbaum)) fisheries and distribution in the
Northwest and Northeast Atlantic. Sarsia, 85, 61-76.
4. Bowering, W. R. & Parsons, D. (1986). Diel Variability in Trawl Catches of
Greenland Halibut from the Channels off Coastal Labrador and Implications for
Resource Assessment. North American Journal of Fisheries Management, 6, 149155.
5. Brodie, W. B., Power, D., & Healey, B. P. (2007). The Canadian fishery for
Greenland halibut in SA 2 + Div. 3KLMNO, with emphasis on 2006. (Rep. No.
NAFO SCR Doc. 07/50 Serial No. N5402). Northwest Atlantic Fisheries
Organization.
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Summary Table:
PBGB LOMA .
Key
Activity/Stressor
a
Bottom trawl
10
c
Greenland halibut > 40 cm (influential predator) within the
d
i
MoI
as
cs
es
(a x c x d x i)
1000
4
7.5 9
2.7
S
(as+cs+es)
3
4
5
3
4.0
Risk
of
Harm
10.8
Cumulative CP Score 10.8
Certainty
Med.