1 / 26

FISHERIES POPULATION DYNAMICS

IKENWEIWE Bolatito Nafisat SENIOR LECTURER DEPARTMENT OF AQUACULTURE AND FISHERIES MANAGEMENT UNIVERSITY OF AGRICULTURE, ABEOKUTA. FISHERIES POPULATION DYNAMICS. titobola2007@yahoo.com , 08033770265. FISHERIES POPULATION DYNAMICS. FIS 507. Catch per unit effort.

benny
Download Presentation

FISHERIES POPULATION DYNAMICS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. IKENWEIWE Bolatito NafisatSENIOR LECTURERDEPARTMENT OF AQUACULTURE AND FISHERIES MANAGEMENTUNIVERSITY OF AGRICULTURE, ABEOKUTA FISHERIES POPULATION DYNAMICS titobola2007@yahoo.com, 08033770265

  2. FISHERIES POPULATION DYNAMICS FIS 507

  3. Catch per unit effort • Calculation for catch per unit effort for the different fishing gears • Passive Gears • Gill Net • Traps • Longlines

  4. Gill Net • Catch weight (Kg) = CPUENo. of bundles • 1 bundle = 30m by 3m • Area of 1 bundle = 90m2 • CPUE often decreases with fishing time

  5. Traps • Catch = kg/trap = aNo. of Trap • a x 24= CPUE per trap per dayfishing hours (12hrs) • Fishing hours (set trap 7.00pm, retrieve by 7.00am = 12 hours =fishing hours) • This is applicable for all traps such Gura, bamboo and wire trap.

  6. Longlines • Catch (Weight) X 12No of lines x fishing time • This is the CPUE per line per 12 hour period which represent longline fishing day. • CPUE in this trap increase with fishing time

  7. Active fishing gears • Cast Net • Drift Net • Dragnet • Beach seine • Spears and harpoons • Trawls and dredges • Seine nets • Purse seines

  8. Cast Net • Cast Net in Kg/day • Catch (weight in Kg) x 24 hours Fishing time • Assuming that total fishing hour is 24 hours.

  9. Drift Net/ Beach • Catch (Kg)No. of Hauls • This gives the CPUE per haul • Since there are always ‘n’ number of hauls per day, • therefore the CPUE will equal CPUE per haul x No of hauls • CPUE decreases as number of hauls per day increases

  10. Dragnet (100m length, 6m depth of Nylon netting material of 25.5 mm stretched mesh). Beach Seine is an active fishing gear • Catch per fleet extrapolated to catch per 1000m2 of net surface area. • Area of a fleet =30m long x 3m = 90m2 • 9 mesh nets (1, 11/2, 2, 21/2, 3, 31/2, 4, 5, 7 and 9 inches) • Therefore 9 x 90m2 = 810m2 • If 810m2 gives ‘x’ weight of fish • 1m2 will give x/180 weight of fish

  11. Therefore, 1000m2 = (x/180) x 1000 weight of fish • X = 10 x 1000 • Where x = sum of all fish caught by all meshes and this is compared to the weight of fish caught by sampling boat (Kg) under commercial catch

  12. Capture of Fishes and Examination of fishes • Terms • Total length is defined as the measurement taken from the anterior-most part of the fish to the end of the caudal fin rays when compressed dorso-ventrally (Anderson and Gutreuter 1983).

  13. Fork length is defined as the measurement taken from the anterior-most part of the fish to the end of the median caudal fin rays (Anderson and Gutreuter 1983). • Standard length is defined as the measurement taken from the tip of the lower jaw to the posterior end of the hypural bone (Anderson and Gutreuter 1983).

  14. Pectoral Fin Pelvic Fin Anal Fin Finlet Caudal Fin Lateral Fin Scutes Opercle Preopercle Interopercle • Total Length • Fork Length • Standard Length • Head Length • Snout Length • Caudal peduncle • Fin Rays • First Dorsal • Second Dorsal Adipose Eyelid Supramaxilla Premaxilla Source: http://www.texasgulfcoastfishing.com

  15. External and Internal Anatomy Source:http://www.kentuckylake.com

  16. Source:http://www.kentuckylake.com

  17. Gill Net Setting and Randomization • Experimental gill nets with graded stretched mesh sizes 1”, 1½”, 2”, 2½”, 3”, 3½”, 4”, 5” and 7” inches • which are equivalent to 25.4, 38.1, 50.8, 63.5, 76.0, 88.5, 101.6, 126.4 and 177.2 millimeters respectively, • Should be set for fish stock assessment while monitoring simultaneously the physico-chemical parameters at each fish sampling station.

  18. Each mesh size of the experimental gill net measuring 30 meters in length and 3 meters depth will be arranged randomly and joined together to form a fleet giving a total surface area of 810m² per fleet. • The nets will be mounted at 50 % hanging ratio. • 1” and 1½” meshes were included in the fleet in order to catch all small fish species in the water body.

  19. Also as fishermen were currently using these meshes (1” and 1½”) to exploit the fishery, • their inclusion in the fleet would give a useful index of abundance in small mesh nets and • the relative catch per unit effort in relation to larger mesh nets

  20. Setting of the Experimental Gill Net during sampling hour of 6-8pm

  21. MARK- RECAPTURE • Reconnaissance visit will be paid to the lake (water body) • Gears to be use must not cause harm or injury to the fish. • Some individuals (fishes) will be captured • Caught fish will be marked/tagged and returned into the water body unharmed • Marking or tagging materials must not be harmful and must be easy to see or detect

  22. After some days/weeks/months (depending on the type of research), a second visit will be paid to the study area • Fishes are captured for the second time and sorted into marked and unmarked • Third, fourth or more visits are can be made • Mark recapture methods rely on some sort of representative sample taken at two different times

  23. Most commonly used mark-recapture estimate of population size is the same as the Lincoln index or Peterson Index which assumes that: • The proportion of individuals which are marked in the population is the same as the proportion of individuals which are marked in a recaptured sample.

  24. M = RN C • M = total individual marked in the population • N = Total population size (which we don’t know but would like to) • R = Number of marked individuals which are recaptured • C = Total number of individuals (marked and unmarked) which are captured in the second trial • N = MC/R

  25. FURTHER READINGS • Ikenweiwe,N.B, D. Odulate, B. Adigun (2011) Ichthyology and Limnology: Tools In Fisheries Management Fisheries Management. United Kingdom. Lap Lambert Academic Publishing. ISBN: 978-3-8433-9364-5. Available online at http://dnb.b-nb.de 127 pages • IkenweiweB. and S. Otubusin (2010). Limnology and Plankton Abundance. Germany. Verlag Publisher. ISBN- 10: 3639253167, ISBN-13: 9783639253160 (Available online at http://www.researchbooks.org/3639253167/LIMNOLOGY-PLANKTON-ABUNDANCE-FISH-PRODUCTION/). 249 pages. • Ita E. O. and M. Mdaihli (1997). The Current Status Of Fish Stock And Fisheries In Kainji Lake

  26. THANK YOU

More Related