Fish Conservation and Management

Transcription

1 Fish Conservation and Management CONS 486 Northern Atlantic Cod: A management and conservation failure Chapter 12 Ross

2 Cod fisheries: rich in history During the early to mid 1900 s, the cod fishery was the most important economic and social component of Atlantic Canada arguably the resource most responsible and influential for the founding and development of Canada in early 1960 s ~ 1-5 million tonnes of cod harvested per year In Cod we Trust

3 Cod fisheries: rich in history since 1992, fishery has been closed except for small localized fisheries In 2007, NFLD/Labrador stock listed as endangered by COSEWIC Other cod stocks listed as threatened or special concern Why the collapse?

4 Fishing approaches primarily used in inshore fishery: Trapnets (the cod trap) Machine jigging Hook-and-line Longlines Gillnets

5 Fishing approaches primarily used in offshore fishery: Purse seines Trawling

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7 Commercial catch data > 800,000 t peak harvest in 1968 Declined steadily to a low of 140,000 t in 1978 BUT increased to 240,000 t in 1980s Collapsed in early 90s (resultant moratorium)

8 Note large foreign catch prior to 200 mile limit, and shift to offshore Canadian fishing

9 Research surveys do not indicate changes in abundance but average size was declining (growth overfishing?)

10 Same size decline in another commercial species

11 Size and abundance declining in noncommercial species - WHY?

12 -caused by discarding and non-reporting of this by-catch -consistent with numerous accounts of discarding small cod -further evidence of growth overfishing

13 - Predation by seals also suggested as a cause but their numbers were not increasing proportionate to the rapid cod decline

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15 More and more fish plants were built with funding from the federal govt who also funded heavily in fleet development, despite declining biomass of capture.

16 Recruitment overfishing of spawning stock!

17 Recruitment overfishing of spawning stock!

18 Why did populations collapse? - growth and recruitment overfishing How did this happen? Socio-economic issues - tragedy of the commons, over-capitalization, ratchet effect - cod fishery was used as the primary social/economic activity - political unwillingness to address the problems (catering to industry) Data issues - short-time series of scientific data, commercial catch data equally influential - unwillingness to deal with uncertainty in scientific abundance estimates - poor management use of data and poor advice to minister - very similar set of events led to the collapse of the US groundfish fishery just south of the border around the same time (read Chapter 12)

19 Role of Fish Behaviour 1980s: abundance didn t change much, why? fisheries surveys commercial catch (abundance increasing!?) 1990s: new hydro-acoustic technology used to assess abundance Revealed cod moving (southward and offshore) into areas where the surveys and offshore fisheries were occurring!! Cod aggregations were concentrating Fisheries yielded consistent catches Surveys likewise affected

20 Are cod recovering? Maybe, but slowly - why? Competition: niche occupied by others (e.g. skates, rays) Climate change not helping (oceans getting warmer) Bottom trawling destroyed spawning habitats

21 Sometimes its hard to know if you are winning or losing the imperilment game! Bring out yer dead! But I m not dead yet..

22 Echograms of cod from the acoustic surveys. Seabed is indicated in dark red, vertical blocks span 1 nautical mile (1852 m), and horizontal blocks span 50 m. In all cases, cod are distributed >100 m off the bottom. (a) June migrating and spawning cod in the Bonavista Corridor (b) March The first observed aggregation in the Bonavista Corridor since 1992 (c) May spawning aggregation in the Bonavista Corridor (d) May spawning aggregation in the Notre Dame Channel

23 Biomass estimated from echograms of cod and their main food capelin from the acoustic surveys. Rose G.A. and Rowe S Northern Cod Comeback. Can. J. Fish. Aquat. Sci. Vol. 72, Since 2011, abundance continues to increase. -Increase in food availability (capelin) is major reason. -Older fish in population also have better condition than in recent past. -All signs of recovery under way

24 Rose G.A. and Rowe S Northern Cod Comeback. Can. J. Fish. Aquat. Sci. Vol. 72, 2015 With continued growth in the capelin stock and frugal management (low fishing mortality), this stock could rebuild, perhaps within less than a decade, to historical levels of sustainable yield. More generally, if this stock can recover, the potential exists for recovery of many other depleted stocks worldwide.

25 What have we learned from the cod collapse? Applied fisheries research: Don t use commercial catch data to estimate stock sizes Research surveys now include acoustics which enables better description of stock aggregations and movements Onboard observers, video surveillance of catch

26 What have we learned from the cod collapse? Management strategies: Reduce and don t encourage further capitalization Use risk-averse management decisions Precautionary approach Do not harvest fish on spawning grounds i.e., protect spawning grounds

27 What have we learned from the cod collapse? Advisory councils: East Coast Conservation Council: industry and govt reps who examine data and advise Fisheries Minister Integrated Management: Transparent process for the public and enables industry to buy-in to decision

28 Atlantic Striped Bass: A management and conservation success. finally!

29 Life history Mature at ~ 3 yrs, > 30 yr max life Fecundity ~ 1 million eggs Size at maturity ranges from cm Anadromous, spawning in rivers, rearing in estuaries and coastal areas along the New England and Carolinian coasts Many similar attributes to cod: life span, fecundity, size, but differ with much early age at maturation and are anadromous

30 History Since 1700s, important commercial species on East coast Recreational species since early 1980 s Hook and line gear predominates in both fisheries In 1972, US commercial landings peaked ~ 6000 tons then dramatically collapsed In Canada: St. Lawrence Estuary population is extinct Bay of Fundy and Gulf of St. Lawrence populations threatened In 1995, US stocks were declared recovered! Why did US pops collapse and recover?

31 Range (US) Chesapeake Bay

32 Declining abundance of outmigrating smolts to the ocean in Maryland and commercial landings both showing similar patterns (large declines from early 70s to early 90s) The science survey data are of good quality, and have been collected for decades prior to the decline. Poor juvenile survival was a result of lower number of returning adults and freshwater habitat problems.

33 Female abundance from spawning grounds showing reduced numbers starting in mid 70s reaching low point in mid 80s. The long term dataset enabled managers to determine what historical levels probably should be, thus could set a restoration goal. This goal was important as part of the restoration/recovery plan for the species.

34 Ability to take advantage of a lucky break! in 1982, by chance, a modestly abundant 8 year group appeared on spawning grounds the management system immediately protected those potential spawners through minimum size limits 3-4 years later, their babies arrived on spawning grounds and those young to mid age classes started to be seen every year

35 Compliance with min size limits this tactic caused an increase in CPUE, and an increase in catch per trip so anglers were very happy!! recreational fishers complied with the min size limits imposed on the 1982 age class and started releasing a lot more fish to the point that almost all were being released by early 90s.

36 Note the growth of the recreational fishery

37 What sequence of events turned the collapse around? Atlantic States Marine Fisheries Commission (ASFMC 13 states involved) ASMFC developed plan - not all states bought in Pressure from commercial sector Stocks continue to decline minimum size limits (14 in bays and 24 along coast) and area closures Resistance by some US states, continued decline federal passage of Striped Bass Act State govts can normally do what they want with fisheries but threat of federal penalties finally got all states into compliance /1985 moratorium placed on 1982 age class Strong class that needed protection Annual increases in minimum size limit protected the 1982 age class juveniles back to levels they were at in late 1960 s ASMFC wants to decrease minimum size which is now at 36 down to 28 but anglers want it to stay! Example of user groups engaged in conservation

38 Stock-Recruit relationships More science! Beverton-Holt Ricker

39 Scientific spawning ground data used to show trends and help managers set thresholds of recovery and upper end targets, anything above the SSB target is surplus for harvesting. The ability to set reference points using scientific data, models, etc is important and unique.

40 Scientific surveys also included ocean trawls Now managers can respond quickly to reduce harvest if warranted

41 Why did populations recover? Fisheries science Good long-term scientific assessment data on freshwater juvenile numbers and adult spawners Anadromous life history so getting data on spawners and outmigrating juveniles much easier than cod Also spawning surveys and recent ocean surveys Life history Have relatively short generation times (unlike cod) and high fecundity Luck!! The occurrence of a strong year class (1982) coupled with Striped Bass Act passing just in time

42 No fishing on spawners Why did populations recover? Fisheries Management Decisions Timely management actions Size limits, closures, moratoriums, rearing habitat improvement Had recovery targets Federal legislation with strong sanctions Interstate issues sometimes need federal solution Public and agencies both wanted to be risk-averse Some freshwater habitat issues were being addressed Unlike cod spawning areas Recreational fishery enabled minimum size limits They bought into the conservation actions Hook & line not damaging spawning habitats (or other species), like with cod trawling