Red Hake Stock Structure Research Track

New England Fisheries

Management Council Meeting

14 April 2020

Research Track process

Working group meetings

(Nov 2019-Feb 2020)

External peer review: Center for Independent Experts

(9-12 Mar 2020)

Products: Working group report

Research track review committeeStephan H. Clark Conference Room-Northeast Fisheries Science Center

Woods Hole Massachusetts9-12 March 2020

Review Committee ChairmanJohn WeidenmannNEFMC Science and Statistical CommitteeRutgers University, State University of New Jersey

PanelistsHaritz ArrizabalagaAZTI, Spain

Christophe PampoulieMarine and Freshwater Research Institute, Iceland

Manuel HildalgoInstituto Español de Oceanografía (IEO), Spain

NOTE

We have seen a draft of the summary report of the

Working Group Chair.

We have not seen individual panelist reports

or the final summary report

Conclusions we present are preliminary and based on our understanding of

their findings

Terms of Reference (shortened)

1. Review and summarize all relevant literature

2. Identify and evaluate any new and/or existing data relevant to the stock structure

3. Recommend the most likely biological stock structure

4. Evaluate existing experimental data on survey catchability of red hake.

5. Apply the existing assessment model. Consider alternate assessment approaches if existing model framework does not perform well.

6. Research recommendations

TOR1: Review stock structure3 stocks managed in U.S. waters plus a 4th on Scotian Shelf during 1970s:

Switched to 2 stocks in 1980s

Historical data on meristics, growth, distribution supported this designation, though other practical factors were considered in delineating stocks

Review panel findings: Term of Reference met

• Fisheries Dependent data

• Trawl survey data (adults)

• Coherence in population trends

• Life history data (growth, otolith appearance)

• Otolith microchemistry

• Spawning and larvae

• Young of the year distribution

• Application of An Index Method

• No Genetic or tagging data

TOR2: New data on stock structure

Panel: Term of reference met with specific questions and comments on the interpretation of certain data

TOR 3: Recommend the most likely biological stock structure among a set of alternatives from TOR2. Consider the current management unit as null hypothesis.

• Growth, distribution, meristics, trends, fisheries-dependent data tend to support current stock structure

• Spawning/larval/juvenile distribution and otolith microchemistry suggest a single stock with Georges Bank a primary spawning ground in summer

• “Working Group concluded that there is not enough evidence to reject the null hypothesis of a two stock structure.”

• Panel agreed with this conclusion

TOR 4: CatchabilityWorking Group Considered:

• Discussions with industry members

• Twin-trawl chain sweep study

• HabCam comparisons to towed gear abundance

• Twin trawl wingspread study

Conclusions

• Data collection and analysis of chain sweep study sufficient

• Current survey gear is 20-25% efficient in catching red hake

Panel agreed that the

conversion factors could be

used to estimate total swept-

area biomass over time for

red hake

TOR5 Part A: Apply the existing assessment model framework to the stock structure based on TOR 3 and 4 to ensure its utility in subsequent management track assessments. Evaluate existing reference points.

• Previous assessment used the AIM model• AIM tests the hypothesis that relative fishing mortality is

driving changes in index values (i.e. index goes up when fishing mortality goes down and vice versa)

• Neither the southern or northern red hake assessment model was significant (South: p=0.457; North: p=0.127)

• Catchability values (TOR 4) can be used to evaluate the FMSY values from AIM

• Estimated FMSY values from AIM were extremely low and not considered reasonable • Southern stock: 0.7% exploitation rate• Northern stock: 0.3% exploitation rate

TOR5 Part B: Consider alternate assessment approaches if existing model framework does not perform well, and consider alternate reference points as needed.

The working group concluded the AIM model should not be used for estimating reference points and stock status for red hake, and the Panel agreed with this conclusion

Alternate assessment approach put forward by working group

• Uses catchability study for estimates of stock biomass and recruitment

• Spawning potential ratio reference points calculated:• life history data (growth and maturity)

• assumed natural mortality rates with uncertainty

• Assumed fisheries selectivity

• 2009-2019 recruitment (spring length cutoff 19 cm)

Using this approach, for both stocksF during past decade below FMSY:

Overfishing not occurring (both stocks)

Both stocks are above BMSY: Not overfished (both stocks)

Fish

ing

Mo

rtal

ity

Spaw

nin

g st

ock

bio

mas

s(1

00

0 m

t)

Northern Stock Southern Stock

F40 with uncertainty F40 with uncertainty

SSB40 with uncertaintySSB40 with uncertainty

F with uncertaintyF with uncertainty

SSB with uncertaintySSB with uncertainty

Alternate assessment approach

Panel review of proposed approach

• Approach was well thought out and potentially useful in future applications

• Sufficient uncertainty in the sensitivity of the reference point estimates to various assumptions made that the reference point estimates should not be used for management advice for red hake at this time

• Methods currently used for setting catch advice for these stocks (witch flounder; GB yellowtail), or other data-limited stocks in the region (e.g., the Plan-B approach) could be explored for both red hake stocks

Panel review of proposed approach (cont.)

Qualitative statements: • The Panel believes that overfishing is not likely occurring

on either stock

• It is unlikely that the northern stock is overfished

• Panel was not able to conclude whether or not the southern stock was overfished

Panel recommendations are just recommendations

NMFS will make the final status determination decisions

TOR 6: Research recommendations

1. Population genetics.

2. Evaluate whether red hake move from the Gulf of Maine to Georges Bank to spawn.

3. Continue aging

4. Otolith microchemistry study

5. Explore an age structured assessment for red hake

6. Further document Fishermen’s Ecological Knowledge for red hake

Working group provided recommendations,

Panel provided detailed advice on how to implement and prioritize these