Presentation - Gulf of Maine Research Institute

Session 3: Broad Scale Stock Structure
A summary and synthesis of Atlantic cod tagging
studies, including movements
Workshop on stock structure of Atlantic cod in the
Gulf of Maine Region
Portsmouth NH, June 12-14 2012
Shelly Tallack
Research Scientist - Applied Fisheries Ecologist
350 Commercial Street, Portland, ME 04101 ・ tel: 207-772-2321 ・ fax: 207-772-6855 ・ www.gmri.org

Overview of cod tagging studies in the region, and available data

Tagging studies and data available for Atlantic cod since 2000
Primary Organization
/Contact
Focus Tag type No. releases No. recaptures Dates
GMRI and partners,
Shelly Tallack
Northeast Regional Cod
Tagging Program: Movement
patterns of cod throughout the
Gulf of Maine, Canadian
Maritimes and Southern New
England waters
T-bar tag (yellow, orange and
blue)
114,467 >6,700
January 2003 – July 2005
(tagging trips); program
overall completed in 2011
SMAST,
David Martins/Steve
Cadrin
Movement of cod tagged in:
Stellwagen Bank, Western
Mass. Bay, Great South
Channel, Georges Bank, Cape
Ann.
T-bar tags (yellow); DSTs in later
years (2005 onwards) to
address spawning fish
movements
>25,000* >1,160* August 2000 to present
UNH,
Hunt Howell
Movement of cod tagged in
Inshore GOM
T-bar tag (yellow and orange) 24,466* 1,835* 2001-2004
UNH,
Hunt Howell
Vertical activity and fine-scale
distribution of cod in Ipswich
Bay spawning ground
DSTs & acoustic tags
200 DSTs and 25
acoustic
26 DSTs (13%),
plus live tracking
of acoustic tags
2006/2007
DFO (St. Andrews),
Don Clark
Movement of cod tagged in the
Bay of Fundy and on the Scotia
Shelf
T-bar tags (orange) 16,922* 715* 2000 – 2003
Stellwagen Bank
Nat. Mar. Sanct.,
James Lindholm
Site fidelity at deep boulder
reefs & Site utilization in
offshore gravel habitat
Acoustic tags 65 56 2003-2005
SMAST,
Doug Zemeckis
Movements of spawning cod in
WGOM
Acoustic tags 63 22 2009-2011
* Tag numbers reflect those data quality controlled and standardized into the same format as the larger Northeast Regional Cod Tagging Program (additional data may
be available).

Data synopsis by region

Analyses undertaken to interpret movement & migration patterns
• Fish size effects (sources for recaptures, by fish size)
• Circular statistics on displacement (distance/direction)
• Investigation into homing patterns
• Seasonal effects (animations of seasonal recaptures)
Mean distance moved (km)
250
200
150
100
50
0
73-92cm
Fall Fall Fall
Recapture season

New analysis - Bivariate boxplot (bagplot) analysis
• Acknowledgement: David Martins
(formerly SMAST, now MA DMF).
• A statistical approach to interpreting
the dispersal of raw release and
recapture data.
• A bagplot = a convex polygon plotted
around a bivariate median of a
distribution (Rousseeuw et al., 1999).
• Identifies areas of recapture density,
but also outlier recaptures.
Interquartile
range
Median dist.
‘Fence’
Outliers
‘Inliers’ (~1.5 times
interquartile range)

Western GOM / Inshore GOM
• Few recaptures came from outside of the I GOM area; offshore movements are
outliers;
• North-south ‘shuffle’ along the coast is evident;
• Defined as ‘sedentary and resident’ by Howell et al. (2008);
• Reiterated by analysis of combined NRCTP, UNH and SMAST data sets.

Western GOM / Inshore GOM

Western GOM / Inshore GOM – Recruitment from Cape Cod

Western GOM / Inshore GOM: Fine-scale studies
• Fine-scale study in Ipswich Bay (Siceloff
& Howell, 2012):
UNH acoustic tracking
(Courtesy Hunt Howell & Laughlin Siceloff)
– Live tracking of acoustic tags (n=26)
– DSTs (n=200 releases, 26 recaptures);
• Verified that the spring spawning group:
– Utilizes a limited area (

Scotian Shelf / Bay of Fundy / Browns Bank

Scotian Shelf / Bay of Fundy / Browns Bank
• NRCTP releases in the B of F:
– Most movements confined to the bay during spring/summer;
– Southward movements to Georges Bank / Georges Basin in fall.
– Little exchange with GOM; contrasts with mixing estimates of 15-20% by Hunt
et al. (1999).
• Historic studies: report a connection between Browns Bank and
the ‘north’ (Scotian Shelf) and ‘north east’ (Bay of Fundy) (Higgins,
1931).

Scotian Shelf / Bay of Fundy / Browns Bank
• Releases in the B of F: move within the bay, and southwards towards deeper
waters of Georges Basin; movements to GB are categorized as ‘outliers’.
• Releases on Browns Bank: dispersed to Bay of Fundy, Georges Bank and
central GOM.

Georges Bank

Georges Bank
• Based on 1,086 recaptures:
– Considerable cross-bank movement;
– Some dispersal evident:
• North to Bay of Fundy and CA waters
• West to inshore waters.
– But, off-bank movements were found to be
‘outliers’;

Cape Cod, Great South Channel, Nantucket Shoals, Block Island

Cape Cod, Great South Channel, Nantucket Shoals
• High tagging effort by the NRCTP
(>50,000 releases); these cod
tended to be smaller (

Block Island
• Relatively few cod found/tagged
in this area until 2005 onwards;
• Movements were mostly limited;
those further afield were ‘outliers’.
• In contrast to historic studies:
little connection with southern
waters of RI and NC (Higgins,
1929; Schroeder, 1930)

Mid-Atlantic Bight (recaptures only)
• Very little information
for this area from
studies since 2000;
• Historic studies:
– Linkages between
southern MA waters and
NC (Higgins, 1929)
– Fall migration from
Nantucket Shoals to
RI/NC region
(Schroeder, 1930).

Proposed “passages” of cod travel (raw data)
GOM (5Y)
SS (4X)
GB (5Z)
Sub-legal cod:
• Recruiting to 2 stocks
• Currently “GB/5Z”

Revised ‘passages’ of cod travel (after bagplots)

Attempts to quantify cod movements for application to stock
assessments

Quantification of exchange between areas – GARM focused
GOM (5Y)
? %
? %
SS (4X)
GB (5Z)
What % is
significant?

Attempts to quantify movements/mixing estimates
• Two attempts on NRCTP data presented at the pre-GARM
workshops:
1. Tallack (2007, 2012): Weighting model(s)
2. Miller & Tallack (2007): Finite-state continuous-time approach (FSTA)
• FSTA model shows most promise for linking with current stock
assessments because it also estimates F and M;
• Further refinement needed for both models before either is
conclusive.
Miller T. & Tallack S. (2007), Estimating instantaneous rates of regional migration and mortality from conventional tagging data. DRAFT REPORT:
Submitted to National Marine Fisheries Service, Pre-GARM working group, WP3D, October 2007. Northeast Fisheries Science Center, Woods Hole, MA:
10 pp.
Tallack, S.M.L., (2007). A description of tagging data from the Northeast Regional Cod Tagging Program (WP3A) and preliminary applications of weighting
and mixing analysis (WP3C). DRAFT REPORT: Submitted to National Marine Fisheries Service, Pre-GARM working group. Northeast Fisheries Science
Center, Woods Hole, MA, Working Papers 3A & 3C, 60 pp.
Tallack, S.M.L., (2012). Stock identification applications of conventional tagging data for Atlantic cod in the Gulf of Maine. Submitted to: Advances in Fish
Tagging and Marking Techniques, AFS, Proceedings from the International Symposium on 'Advances in Fish Tagging and Marking Techniques', Auckland,
NZ, February 24-28th, 2008.

Major conclusions from tagging data with regard stock structure

Key conclusions from tagging data
1. The connection between Cape Cod fish (5Z) and the Inshore
GOM stocks (5Y) appears to be unquestionable - Inshore GOM
fish appear relatively resident to the area, with additional
recruitment of younger fish from waters around Cape Cod.
2. Georges Bank fish are a largely self-sustaining offshore
population that mixes with the Scotian Shelf and Bay of Fundy
fish.
3. The Bay of Fundy retains a good portion of its cod, but mixing
with the offshore banks (Georges Bank and Browns Bank) is
also evident.
4. From recent movement studies, little can be said about cod in
the Mid-Atlantic Bight and more southern waters.

Current and alternative stock management boundaries
Alternative 1
Current
Alternative 2

Additional research required for stock structure determination

• Many gaps remain in our understanding of GOM cod population structure:
– Some answers may come from additional analyses on current tagging data.
– Additional integrated spatial studies are also needed (tagging, movement, genetic,
habitat, environmental…).
• Top research priority:
“Recent and historical cod tagging data (and genetic data) suggest
substantial movements across current stock boundaries and considerable
heterogeneity within current management units. Best available science
indicates the need to re-visit, re-analyze and re-assess the stock
management boundaries.”
Tallack, S.M.L., 2009. Proceedings from a workshop to identify future research priorities for cod tagging in the Gulf of Maine. Northeast Fisheries Science
Center Reference Document. US Department of Commerce, 09-09, 76 pp.

Key research needs outlined
• Theme 1 – Cod Management:
– Interdisciplinary assessment of cod management boundaries;
– Investigate options for alternative management scales;
– Expand research to earlier life-stages.
• Theme 2 – Data mining, re-analysis, modeling:
– Meta-analysis of historical mark-recapture datasets (particularly for the period
since 2000);
– Stock assessment applications of tagging data and parameters we can derive
from these data, e.g. natural mortality, fishing mortality, growth, selectivity.
• Theme 4 – Reporting rates/outreach efficacy – to improve our
interpretation of tagging data.

Key research needs outlined (cont.)
• Theme 5 – Additional deployment of tags on cod:
– Juvenile cod: habitat usage, movements, dispersal from nursery grounds to
adult stocks;
– Spawning cod: address all major spawning grounds to investigate, natal
homing, long-term spawning movements, timing of spawning, critical habitats,
etc.;
– Fine-scale investigations to improve our understanding of critical habitats;
– Multi-year, long-term tagging with consistent tag releases over time and by
area;
– Advanced tagging technologies, e.g. acoustic arrays in strategic areas;
– Closed-area investigations: critical habitat, size, timing, etc;
– Incorporate additional ecology & biology within future tagging studies.

Acknowledgements
• Analytical contributions by: Steve Cadrin (SMAST), Mark Terceiro
(NEFSC), Loretta O’Brien (NEFSC), Ralph Mayo (NEFSC), Tim Miller
(NEFSC), David Martins (MA DMF), and Don Clark (DFO).
• Data contributions by: Northeast Regional Cod Tagging Program; Hunt
Howell (UNH); Don Clark (DFO); David Martins (SMAST).
• These studies would not be possible without the effort invested by various
funding bodies, including NOAA’s Cooperative Research Program, and
numerous scientists and members of the commercial and recreational
fishing industry. See www.codresearch.org for full list.
~50 scientists >106
vessels