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Lake Nipissing: Ecology & Fisheries

Lake Nipissing: Ecology & Fisheries. Richard Rowe, Senior Biologist. Lake Nipissing: The Last 100 Years. Pre-World War I: Blue phase, shadflies & sturgeon decline World War I: The Beef & Bacon Initiative 1940s & 1950s Tourism, Yellow ‘seeding’, 1 st Blue-Green report

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Lake Nipissing: Ecology & Fisheries

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  1. Lake Nipissing: Ecology & Fisheries Richard Rowe, Senior Biologist

  2. Lake Nipissing: The Last 100 Years • Pre-World War I:Blue phase, shadflies & sturgeon decline • World War I:The Beef & Bacon Initiative • 1940s & 1950sTourism, Yellow ‘seeding’, 1st Blue-Green report • 1960s & 1970s Tourism explosion, Fisheries assessment, ice fishing, blue ‘phased’ out

  3. Lake Nipissing: The Last 100 Years • 1980s to mid 1990sRecreational fishing concern, NFN commercial fishery emerging • Mid 1990s to early 2000sNFN commercial fishery concern, loss of fisheries assessment • Mid 2000s to 2010Significant Management Efforts, Walleye fishery slowly improving? • 2010-presentWalleye fishery decline, ecosystem shifts

  4. Habitat Changes • The creeping crisis • Loss of diversity; loss of insurance

  5. Species Introductions & Re-colonization • Always a risk of upsetting the ecosystem balance

  6. Most Recent Changes in Ecosystem Arguably the biggest changes: Other Notable Changes: • Energy Flow changes in food web from zooplankton to walleye • Herring • Smelt • Walleye observed feeding on smelt; growth changes, movements?

  7. Present Day Lake Nipissing Ecosystem: The Walleye • Lake-wide, the top predator and greatest top-down influence on ecosystem (this could be changing) “The most significant population stress on Lake Nipissing walleye continues to be human exploitation”

  8. Monitoring the Walleye & the Impacts We Have On It • Fall Walleye Index Netting (FWIN) • Daily Commercial Harvest Reporting • Angler Creel Surveys (Other data sets, other species)

  9. Walleye “Management” - Considerations Q: How do you manage walleye? A: You Don’t Fish manage themselves – we try to manage our impacts when needed. Best way to manage impacts on walleye: • Protect spawning population = protect the future

  10. The Reasons are in the biology: • A 4-lb female lays 100,000 eggsSo?If there are enough adult walleye left and they spawn, they can increase the population quickly (IF conditions are right and IF there are enough) • Lake Nipissing is ideal habitat for walleyeSo?If weather conditions are suitable and there is a enough spawning fish, Lake Nipissing walleye will produce strong year classes The Key to Management – Keep Enough Spawning Fish in the Lake

  11. Stock Status Upper Stock Reference Point Limit Reference Point Harvest Level Maximum Harvest Level Total Harvest Level Critical Cautious Healthy Approach: Adaptive Management • A combination of science and ‘trial and error’ • The Science: Maximum Sustainable Yield • The Trial/Error:Maintain a harvest significantly lower than this, protect spawning fish and see what happens…

  12. Angler Harvest Control directed at Spawning Fish • Recreational angling fishery protected slot size • Angling season opens after spawn

  13. NFN Management efforts to protect spawning walleye • Mesh size (minimizes kill of larger spawners) • Moratorium (guarantee fish left to spawn) • Quota (guarantee fish left to spawn) • Reporting harvest (keeping track)

  14. Signs of Modern Management Working? Since 2004 (when slot started/NFN started): Spawning stock every year for 5 years in a row (numbers and biomass)

  15. NFN formal mgmt Slot Size Index Nets – wt. walleye > 40 cm Signs of Management Working? Despite all other stresses on ecosystem to this point, management efforts seemed to be working…

  16. Harvest seems to be at level that allows slow increase of spawning stock Estimated Safe Harvest Level (Maximum sustainable) Harvest (kg) Total of all walleye harvested (sport + commercial) NFN formal mgmt Slot Size

  17. Something happened in 2009 • Number of spawning walleye in index netting • Management stayed the same – reported harvest at desired level • Suspicion that ecosystem was changing…again • One bad year of data or was this a real change?

  18. THE Alarming Trend: Spawning Stock

  19. THE Alarming Trend: Spawning Stock

  20. What Happened? • Many contributing factors likely played a role: harvest, ecosystem, nature cycles • No one specific cause for the latest decline

  21. Harvest STILL Drives the Fishery?

  22. Harvest STILL Drives the Fishery?

  23. Harvest STILL Drives the Fishery?

  24. Harvest STILL Drives the Fishery?

  25. Harvest STILL Drives the Fishery?

  26. Harvest STILL Drives the Fishery?

  27. Harvest STILL Drives the Fishery?

  28. IF Harvest Still Drives Fishery: • Extra harvest had to occur in 2009 and 2010 X X

  29. Can we “find” extra or unexpected harvest in 2009, 2010 to make sense of existing data? Confirmed Sources: • Non-compliance NFN moratorium (ballpark #’s based on occurrences) • Commercial spearing possibilities (ballpark numbers based on weather) • Undetected angler non-compliance with slot size (ballpark numbers based on Alberta model) • Dokis FN commercialization (ballpark #’s based on confirmed reports)

  30. Extra Harvest Factor:

  31. Extra Harvest Factor:

  32. What Happened - Final Thoughts • Should we have done more in 1998; 2004? • Did we let our collective guard down for compliance during a time when it was needed most? • Did we live off the ‘principle’ of the fishery during times of record low interest? • Did we get unlucky from a weather and cyclical perspective? Varying degrees of “Yes” to all of these…

  33. Where Does This Leave Us Moving Forward? The Ecosystem • In a state of flux • SWF abundant, • Yellow perch dominant, • Walleye’s place uncertain

  34. Where Does This Leave Us Moving Forward? The Walleye Fishery • Seem to be ‘skinnier; maturing a bit later • This + the ‘double gauntlet’ is leading to or has led to a serious situation called ‘recruitment overfishing’

  35. Age 0-1 Age 2-3 Age 3-4 Age 5-7 Age 8+

  36. Age 0-1 Age 2-3 Age 3-4 Age 5-7 Age 8+

  37. Recruitment Overfishing ? Age 0-1 Age 2-3 Age 3-4 Age 5-7 Age 8+

  38. Where Does This Leave Us Moving Forward? The Challenge for the Future • Record numbers of young captured in FWIN 2 yrs in a row • Can we get them through to become prime spawning stock?

  39. Where Does This Leave Us Moving Forward? The Challenge for the Future • Record numbers of young captured in FWIN 2 yrs in a row • Can we get them through to become prime spawning stock?

  40. Where Does This Leave Us Moving Forward? The Challenge for the Future • How do we assure that enough of these young make it through? • Chances for success depends on both major fisheries • IF we make it through – how do we get better compliance during those ‘lean years’?

  41. The Next 5 Years: Our Biggest Crisis or Our Greatest Opportunity?

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