Atlantic Halibut [Hippogossus hippoglossus] Range Expansion into - - PowerPoint PPT Presentation

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Jul 12, 2023 49 likes •511 views

Atlantic Halibut [Hippogossus hippoglossus] Range Expansion into Suitable Habitat and the Role of Closed Areas in the Northwest Atlantic Nancy L Shackell, Kiyomi French Oceanography and Climate Section, Ocean and Ecosystem Sciences Division

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Atlantic Halibut [Hippogossus hippoglossus] Range Expansion into Suitable Habitat and the Role of Closed Areas in the Northwest Atlantic

Nancy L Shackell, Kiyomi French

Oceanography and Climate Section, Ocean and Ecosystem Sciences Division Bedford Institute of Oceanography, Fisheries and Oceans, Canada

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Overview

  • 1. Management and history of Atlantic halibut

in Atlantic Canada

  • 2. Habitat Suitability
  • 3. Trends
  • 4. Model:

– Effects of fishing and temperature – Effects of closed areas

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Management and history of Atlantic halibut in Atlantic Canada

  • Two management units
  • Both experiencing a period of high

juvenile recruitment

  • History of over exploitation and

serial depletion.

  • Both as bycatch in cod fishery

and in directed halibut fishery

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

1977- Exclusive Economic Zone (EEZ), closed to foreign fisheries = dramatic reduction in landings and increase in abundance of all groundfish species

EEZ

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

Establish Total Allowable Catch (TAC) and minimum fish length (81cm) in halibut fishery

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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Atlantic Ocean

Newfoundland Gulf of Saint Lawrence

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  • Dotted line represents cod moratorium (1992-1994)
  • Noticeable dip in biomass around time of cod moratorium
  • Currently experiencing a period of high recruitment
  • Spatial aspect: Rate of increase varies across stock area

Abundance Trends

South North

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Habitat suitability? Fishing? Temperature?

What variables are influencing / shaping this resurgence?

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Habitat Suitability

(French et al. in press)

Found relation between relative availability of suitable habitat and relative landings (recent and historic)

  • Consistent with

nursery size hypotheses

  • Suggests spatial

structure is more complex than previously assumed

  • Also suggests lower

levels of migration

  • Considerable

amounts of unoccupied- yet suitable habitat

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Habitat Suitability

(French et al. in press)

Found relation between relative availability of suitable habitat and relative landings (recent and historic)

  • Consistent with

nursery size hypotheses

  • Suggests spatial

structure is more complex than previously assumed

  • Also suggests lower

levels of migration

  • Considerable

amounts of unoccupied- yet suitable habitat

Habitat Suitability Value

0 - 0.25 àPoor 0.26 – 0.50 àMarginal 0.51 – 0.75 àGood 0.76 - 1 àOptimal

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Habitat Suitability (2/2)

South North

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Temperature Trends

Designer plotting by Torkild Tverraa

  • Most optimal habitat corresponds with warmer waters
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Occupancy Trends

  • Higher occupancy in

more suitable regions

  • Probability of

increase over time is less in peripheral regions

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Fishing Before and After Moratorium

  • Landings of cod, halibut and
  • ther groundfish have

decreased dramatically since the cod moratorium (1992-1994)

https://www.nafo.int/Data/STATLANT NAFO Before After Difference 2J 1960.1 44.9

  • 1915 (98%)

3K 2492.1 86.6

  • 2405 (97%)

4Vn 637 19.6

  • 617 (97%)

4Vs 967.8 29.6

  • 938 (97%)

Change (Million kg)

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Fishing Trends

https://www.nafo.int/Data/STATLANT

  • Always relatively high

in 3P

  • Also high in 4X and

5YZe (no cod moratorium )

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Holding all else constant, is the presence of halibut influenced by temperature and/or fishing?

Best Model:

  • Generalized linear mixed effects model
  • Presence : binomial response
  • Random effects: Year, NAFO, habitat

suitability

  • Interactions: Fishing (cod & halibut landings),

temperature

Model:

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  • Higher in the gulf of saint Lawrence and
  • n the Scotian Shelf
  • Lower in more peripheral and/or

northern regions

Model Estimates

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Model Estimates in odds ratios

Halibut presence is influenced by temperature and fishing

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  • Persistent core areas in

times of low abundance located on Browns bank and on top of the Gully and their relation to fishery closures …Core areas in 3OP never returned post- moratorium (Boudreau et al, 2017)

Do fishery closures play a role?

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Name NAFO Year Closed Closure Type Browns Bank 4X 1972 Feb 1- June 15 Haddock Box 4W 1993 Year- round 4VsB 4VS 1995 Jan 1- April 30

Closed Areas

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What is the effect of closed areas and temperature holding all else constant?

Best Model:

  • Generalized linear mixed effects model
  • Presence : binomial response
  • Random effects: Year, NAFO, habitat suitability
  • Interactions: Fishery Closure (binomial),

temperature

Model:

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Model Estimates in odds ratios Halibut presence is influenced by temperature and closed areas

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Range expansion and secondary role of closed areas

Higher presence in more suitable habitat, abundances increasing annually in all types, suggesting continued growth Fishing, temperature and Fishery closures influence the probability of halibut being present in a given year, habitat suitability type and NAFO region. Higher presence values on the scotia shelf and in the Gulf of Saint Lawrence. Lower in Newfoundland and the United States, where landings are relatively high, and less closures .

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(Nancy Shackell, Nell den Heyer, Kiyomi French/DFO, Canada) Connectivity Current=2000km; Estimated=250km Mature female Residents: 6 km

Winter Migration: <250km

Size of Juvenile Habitat ~ Adult landings

Q: Are the following consistent with current stock unit domain?

Life history trait Working Hypothesis: multiple sub stocks?

  • Is one sub stock rescuing another?
  • Does management strategy appropriately allocate TAC’s and are we

handicapping recovery in some areas? Genetic landscape (in progress)

44 Shackell et al. 2016 ICESJMar, Boudreau et al. 2017 Ecol&Evol French et al. in press. Fish Bull.

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Thank you

  • IFS
  • IGS
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Model Estimates

NAFO 4w 4X 4Vs Habitat Suitability Marginal Optimal

NAFO intercepts are comparable Optimal habitat = higher presence