350 likes | 469 Views
Factors affecting the catch rate of American lobster in the eastern Gulf of St. Lawrence. Daniel Gillis 12 th Annual Brace Research Day April 5 th 2013. "The worst day of fishing is still better than the best day at work." -Unknown . Lobster Fishing in Atlantic Canada.
E N D
Factors affecting the catch rate of American lobster in the eastern Gulf of St. Lawrence Daniel Gillis 12th Annual Brace Research Day April 5th 2013 "The worst day of fishing is still better than the best day at work." -Unknown
Lobster Fishing in Atlantic Canada Major contributor to many coastal economies for almost 200 years Lobster exports for 2012 NS – 26,000 t ($374 Million) NB – 22,000 t ($475 Million) PEI – 6,000 t ($37 Million) http://www.dfo-mpo.gc.ca/media/back-fiche/2013/hq-ac03a-eng.htm
My father, youngest brother, and myself having lunch in 2011
Juvenile (left) and exceptionally large female lobster (right)
Influence of Environmental Factors Fishermen have long noticed that: As water warms, catch rates increase… Westerly winds increase catch rates… Easterly winds decrease catch rates…
Scientists have shown that… ΔCatch = k · Δtemp (As temperature inc. or dec., catch rates follow) Drinkwater et al. 2006. Fish. Oceanogr. 15:150-165
Scientists have shown that… Wind influences water temperature through up/downwellings of cold/warm water Caused by Ekman currents Drinkwater et al. 2006. Fish. Oceanogr. 15:150-165
Ekman currents Net movement of water perpendicular to wind direction http://booksite.academicpress.com/DPO/chapter07.html
My B.Sc. Thesis Research NSERC Undergraduate Student Research Award May – August, 2007 Study Objective: Investigate environmental and fishing strategy variables that may affect the catch rate of lobster
Study Design Catch rates measured on 41 different days: Total Weight Market Weight Canner Weight Number per Trap (Sampled from 6 locations) Juveniles Temperature measured daily at 9 and 18 m depth Analysis using multiple linear regression and repeated measures ANOVA
Results Significant linear relationships (p < 0.05) with Catch Rates vs. Temp. and Time Moderately strong (R2 adj. = 0.481 to 0.680) Bait use not significant
Habitat Locations Analyzed Separately Time was still significant at 5 of 6 locations Temperature only significant at 2 of 6 locations Repeated Measures ANOVA revealed a significant day × location interaction
Conclusions Day-to-day variability in catch rates linked to temperature Accumulated fishing time has an increasing negative effect on catch rates
Conclusions At a spatial scale smaller than the entire habitat, effect of temperature not as strong Interaction between day × location suggests non-random (patchy) distribution of lobsters
Thank you for your attention Questions? Setting day last year, May 1st 2012
Thank you for your attention Questions? Ominous weather, June 2007
Thank you for your attention Questions? A visitor, May 2007
Thank you for your attention Questions? A beautiful day on the water, May 2007
Thank you for your attention Questions? A rare blue lobster, June 2007
Thank you for your attention Questions? Just another day on the water, June 2007
Thank you for your attention Questions? Breakwater at Inverness Harbour, June 2007