Fleet Dynamics of the Atlantic Sea Scallop Fishery Paul Rago and Dvora Hart National Marine Fisheries Service Northeast Fisheries Science Center Woods Hole, MA 02543
Objectives of Presentation Describe offshore Scallop Fishery Factors Influencing spatial and seasonal distribution of fishing effort Implications for harvest and management Interactions with habitat and bycatch
e ud a ti t L Longitude -76-74 -72-70 -68-66 42.5 42.5 41.2 41.2 39.9 39.9 38.6 Oct 1999 38.6 Oct 1999 37.3 37.3 36.0 36.0-76 -74-72 -70-68 -66 Longitude
Scallop Fishery (1) Georges Bank to Virginia: 40-100 m depth 2nd most valuable in Northeast: 2000 $150M Historic range well below potential 40-60 M lb ~250 vessels, 90% dredge 120 Days at Sea ~ 25000 vessel days, down from 60,000 in early 1990s Effort Controls: Crew, Rings, Twine top Vessel Tracking and Monitoring System 1998 Mandatory
Vessel Tracking System Hourly position and velocity measures by geosynchronous satellite Pooled by 1 nm sqr quadrats Computed ave speed, duration, duration at speeds <5 knots Ship velocity < 5 knots ==> fishing activity Travel time=total time- fishing Activity Area Swept ~4.5 knots*30 ft*6076 ft/nm * Fishing Activity
Scallop Fishery (2) Closed Areas: 3 Georges Bank since Dec. 1994 2 Mid Atlantic since April 1998 Reopenings--steps toward rotational management Area II 1999, 2000; Area I 2000-2001 Nantucket Lightship 2000 Hudson Canyon & Virginia Beach 2001
Effects of Density and Size on Exploitation Patterns
Latitude Latitude Longitude -76-74 -72-70 -68-66 42.5 42.5 41.2 41.2 39.9 38.6 37.3 Fishing Time 1998 1998 Fishing Time hours/nm^2 blue <2 green 2-9 yellow 9-44 red >44 39.9 38.6 37.3 36.0 36.0-76 -74-72 -70-68 -66 Longitude
Latitude Longitude -76-74 -72-70 -68-66 42.5 42.5 41.2 41.2 39.9 38.6 37.3 Fishing Time 1999 1999 Fishing Time hours/nm^2 blue <2 green 2-9 yellow 9-44 red >44 39.9 38.6 37.3 36.0 36.0-76 -74-72 -70-68 -66 Longitude Latitude
-76-74 -72-70 -68-66 42.5 42.5 41.2 41.2 39.9 38.6 37.3 Fishing Time 2000 2000 Fishing Time Hour/nm^2 blue <1 green 1-5 yellow 5-38 red >38 39.9 38.6 37.3 36.0 36.0-76 -74-72 -70-68 -66 Longitude Latitude
50000 40000 30000 20000 10000 0 1998 0 100 200 300 400 500 Fishing Activity (hr) Landings (lbs)
50000 40000 30000 20000 10000 0 1999 0 100 200 300 400 500 Fishing Activity (hr) Landings (lbs)
50000 40000 30000 20000 10000 0 2000 0 100 200 300 400 500 Fishing Activity (hr) Landings (lbs)
Landings per sqr. Mile vs Fishing Activity (hr) 50000 40000 30000 20000 Landings (lbs) 10000 0 2500 lb/day ~Max shucking capacity 2000 1999 1998 0 100 200 300 400 500 Fishing Activity (hr)
Footprint of the Fleet
1 0.8 0.6 0.4 0.2 0 Concentration of Landings Profiles for Scallop fishery in 1998,1999, and 2000 0 5000 10000 15000 Footprint of Fishery (nm2) CDF_2000 CDF_1998 CDF_1999 Fraction of Total Landings
Comparison of Concentration Curves for Landings in a low density year 1998 and 1999, a year in which landings were augmented by access to the Closed Area II. 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 An additional 1424 nm^2 were fished in 1998 to achieve 90% of landings Fraction of Total Landings 0 5000 10000 15000 CDF_1998 CDF_1999 Footprint of Fishery (nm2)
Density-dependent fishing mortality is strong... 40 20 10 5 Mean meat weight (g) 2 10 100 1000 10000 Number of scallops Georges Bank, 1982-1994 (Hart. 2001. CJFAS 58:2351-2358)
...but there is no evidence of density-dependent natural mortality. 40 20 10 5 Mean meat weight (g) 2 10 100 1000 10000 Number of scallops Georges Bank closed areas (excluding CA2-S), 1999-2000
Georges Bank 2000 closed area size-frequencies (excluding CA2-S), together with projected size-frequencies assuming standard and fast (K=0.4) growth (from SARC-32). 70 60 Observed in 2000 survey Projected from 1995 survey with std growth Projected from 1995 survey with K = 0.4 50 40 30 Number/tow 20 10 0 60 80 100 120 140 160 Shell height (mm)
1999 --Area II Fishery Reopens life does not stand still while specialists put their minds in order Michael Graham, 1950 Address to United Nations
Spatial Distribution of Bycatch Yellowtail/Scallop Ratio 1998, (number YT/bushels Scal) 2 8 6 2 4 41.5 41.4 12 10 8 10 4 6 41.3 41.2 LATITUDE 6 6 41.1 4 8 10 8 12 41.0-67.50-67.25-67.00-66.75-66.50-66.25 LONGITUDE
Latitude (deg) 41.5 41.4 41.3 41.2 Area II Reporting Locations: Before Oct 1 > 2500 lb/day 1850-2500 lb/da 1500-1850 lb/da 1100-1500 lb/da < 1100 lb/day 41.1 41.0-67.50-67.25-67.00-66.75-66.50-66.25 Longitude (deg)
Latitude (deg) 41.5 41.4 41.3 41.2 Area II Reporting Locations: After Oct 1 > 2500 lb/day 1850-2500 lb/d 1500-1850 lb/d 1100-1500 lb/d < 1100 lb/day 41.1 41.0-67.50-67.25-67.00-66.75-66.50-66.25 Longitude (deg)
BYCATCH AND DISCARD CONSIDERATIONS YT Discard ratio in Area II Exemption Fishery, 1999 0.4 0.45 0.35 0.3 0.25 0.2 0.15 0.1 0 0.05 Before Oct 1 After Oct 1 Discard Ratio (YT lb to Scallop lb) 20 25 30 35 40 45 YT discard ratio Week
Latitude Spatial Economics: Revenue per square nautical mile Longitude -76-74 -72-70 -68-66 42.5 42.5 41.2 41.2 39.9 38.6 Latitude 37.3 Total Value 1999 1999 Total Value $/nm^2 blue <320 green 320-1404 yellow 1404-6271 red >6271 39.9 38.6 37.3 36.0 36.0-76 -74-72 -70-68 -66 Longitude
Latitude Meat Count Distribution: Where might overfishing occur? 42.5 Longitude -76-74 -72-70 -68-66 42.5 41.2 41.2 39.9 38.6 Latitude 37.3 1999 Landings: 40-70 Count lb/nm^2 blue <1 green 1-10 yellow 10-73 red >73 Q6t8: 40-50, 50-60, 60-70 count 1999 39.9 38.6 37.3 36.0 36.0-76 -74-72 -70-68 -66 Longitude
Some Basic Conclusions from VMS Data Fishing activity occurs over about 12,000 sqr nm, BUT 75% of total effort occurs in less than 3,000 sqr nm. Primary scallop areas experience about 110 hours of fishing activity per year In 1999, primary scallop areas generated 88% of landings and revenue Primary scallop areas generated about $33,000 of landings per sqr nm in 1999
Advantages of VMS Common Language integration of survey, at-sea observers, landings, enforcement and management Timely and Detailed Enables Adaptive Management Improved Surveys Design of Area Rotation Habitat and Bycatch Tradeoffs Improved Theory/Models
Where do we go from here? Rotational Area Mgt Biological Reserves for spawning stock Hydrodynamic models to develop reproductive footprint Experiments within SFA Explicit consideration of tradeoffs: habitat and bycatch Stewardship/ownership
Figure 4.Multibeam bathymetric image of western Browns Bank,western Scotian Shelf.The image shows colour-coded depths and is artificially-shaded from the northwest to enhance the portrayal of morphology.prominent features include bouldery ridged moraines,fields of sandy bedforms,shelf-edge low stand deltas,and a variety of other subtle terrain types.the bank is largely formed of glacial materials,reworked and modified by a transgressing sea in post glacial time.both glacial (relict)and modern (present day)seabed features occur adjacent to one another.
Seasonal Average Weights for Scallops (1987-1988) Serchuk and Smolowitz (1988) 30 25 20 15 10 5 0 Shell Height 87 mm 92 mm 97 mm 102 mm 107 mm jan feb mar apr may jun jul aug sep oct nov dec Month Average Meat Weight (g)
50 40 30 20 10 0 Fraction of time that Wave Height exceeds 2.5 meters By Station Georges Bank Nantucket Lightship Long Island Delaware Bay Virginia Beach 0 2 4 6 8 10 12 Month Offshore-Cape May Percent of Month
60 40 20 0 Comparison of Seasonal Patterns in Wave Height (percent observations >2.5 m) and Ave Wt (g) of Scallops at 107 mm Shell Height Georges Bank Jan Mar May Jul Sep Nov Month 30 27 24 21 18 15 Nantucket Lightship Long Island Delaware Bay Virginia Beach Percent of Month Ave Wt (g) at 107 mm Offshore-Cape May Ave Wt @ 107 mm
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