preliminary demographic analysis of the shortfin mako shark isurus oxyrinchus
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Preliminary demographic analysis of the shortfin mako shark, Isurus oxyrinchus. Mollet H. F. and Cailliet G. M. Contrasting VBGF and Reproductive Parameters for the Shortfin Mako Pratt and Casey 1983 vs. Cailliet et al. 1983.

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preliminary demographic analysis of the shortfin mako shark isurus oxyrinchus

Preliminary demographic analysis of the shortfin mako shark, Isurusoxyrinchus

Mollet H. F. and Cailliet G. M.

slide2
Contrasting VBGF and Reproductive Parameters for the Shortfin MakoPratt and Casey 1983 vs. Cailliet et al. 1983
slide3

Age at Maturity of Female Shortfin Mako(when 10 and 90% are mature)1. L (t) = 3.73 - (3.73 - 0.70) e(-0.203 t), Pratt and Casey 19832. L (t) = 3.21 - (3.21 - 0.76) e(-0.072 t), Cailliet et al. 1983

slide4

Observed and Calculated (from VBGF) Growth Rates for the Shortfin Mako1. L (t) = 3.73 - (3.73 - 0.70) e (-0.203 t), Pratt and Casey 19832. L (t) = 3.21 - (3.21 - 0.76) e (-0.072 t), Cailliet et al. 1983

growth rates of southern california makos from modes of length frequency histograms
Growth Rates of Southern California Makos from Modes of Length-Frequency Histograms
  • ~50 cm/yr at age 0.25 yr~34 cm/yr at age 1 yrFall data Cailliet et al. 1983 assuming 2 bands/year.
  • ~45 cm/yr at age 0.67 yr~30 cm/yr at age 1.67 yrO\'Brian and Sunada 1994, modes at AL = 42 and 53 cm (TL = 122 and 152 cm) from 2+ and 3+ year old makos, respectively.
  • ~60 cm/yr at age 0.25 yr~30 cm/yr at age 1.0 yr20-25 cm/yr at age 2.0 yrHanan et al. 1993, modes at AL = 34, 44, and 54 cm (TL = 100, 130, and 150-150 cm) from 0.5, 1.5 and 2.5 year old makos, respectively.
d09 to be completed if needed
D09 To be completed if needed
  • 2 bands per year (Atlantic) vs. 1 band year (Pacific)?
  • No reliable data until 1994
  • Parker, H. W. and F. C. Stott 1965. Age ,size, and vertebral calcification in the basking shark Cetorhinus maximus (Gunnerus). Zoologische Mededelingen (Leiden) 40, 305-319. Received 1/21/97
  • Comparison of age/length relationship with length/rings relationship suggested 2 rings (=bands?) per year and a gestation time of 3.5 years (7 rings (=bands? at birth
  • Was questionend by Pauly 1978 (not seen by me)
  • Holt and Bedford 1993. Used 3 makos with TL = 1. 7 and 1.8 m in tagging study and used Pratt and Casey 1983 to estimate age of 2-year old juveniles.
  • Branstetter and Musick 1994. 2 Bands/year for the sandtiger
catch curves estimation of survival from age composition ricker 1977 krebs 1989
Catch Curves Estimation of Survival from Age Composition(Ricker 1977, Krebs 1989)
  • Right limb is a survivorship curve that is both age-specific and time-specific if the following assumptions are met:
      • Survival rate is uniform with age
      • Survival rate is uniform with time
      • Sample taken randomly from age groups involved
      • Recruitment is constant for all age groups
  • If these 4 assumptions are violated, the right limb of the catch curve will often not be a straight line.
slide12
Catch Curve for Exp. Drift Longline Fishery in Southern California during 1988-1991O\'Brian and Sunada 1994
slide13

Catch Curve for Makos taken by Japanese Longliners off the eastern coast of Australia(Stevens 1992)can add n=98 females, Z = 0.61 but # to small to derive meaningful catch curve. Could try smoothing.

slide14

Catch Curve for Shortfin Mako off East Northland and Bay of Plenty, New Zealand 1974-90 (Saul and Holdsworth 1992)(females extracted and large females from off-shore added)

slide15
Catch Curve for Female Shortfin Mako from western North Atlantic, n = 1113 (Casey and Kohler 1992)Z= 0.70, too large! but why,
slide17
D? Mejuto for years 1983 and 1984combinend female data for the 2 years then calculatet age_FL. Was done later!
parameters for demographic analysis
Parameters for Demographic Analysis
  • 1. Length at Age (VBGF).
  • 2. Estimate of natural mortality (M) Hoenig 1983 (requires max. age estimate, we used 7 ln2/k = 23.9 years (k = 0.203 year-1).Pauly 1974 (requires max. size = 3.73 m TL, VBGF k = 0.203 year-1, and water temperature T = 20 C.
  • 3. Estimate of fishing mortality (F) or total mortality (Z = M + F); we used catch-curve derived Z.
  • 4. Natality, to be discussed next.
slide20

Effective Natality vs. TL10, 50, 90% mature at TL = 2.60, 2.72, 2.85 m)mx(TL) = (1/4) 0.572 TL2.66e(-47.481+17.505 TL)/(1+e(-47.481+17.505 TL));

slide21

Effective Natality vs. Age10, 50, 90% mature at age 4.8, 5.4, 6.1yrmx = (1/4) 0.572 TL2.66.e(-47.481+17.505 TL)/(1+e(-47.481+17.505 TL));with TL = 3.734-(3.734-0.702)e(-0.203 age)

slide22

Life-History Table of Isurus oxyrinchusInput: VBGF, Z = 0.30 year-1, mx = effective natalityOutput: Ro = 2.0, G = 9.0 year, r = 0.076 year-1, er = 1.08

slide23

Life-History Table of Isurus oxyrinchusInput: VBGF, Z = 0.34 year-1, mx = effective natalityOutput: Ro = 1.08, G = 9.72 year, r = 0.0084 year-1, er = 1.01

slide24

D23 To be finalized if needed. Got a slight problem because Z derived from the corresponding catch curve is expected to be 0.34 (input) and not 0.348

slide27
Life History Parameters for Isurus oxyrinchususing 3-Year Reproductive Cycle (F= 0.05 and 0.10 year-1start at age 0)
slide32
Finite Rate of Population Change (er) vs. Z(Southern Hemisphere vs. Western North Atlantic Age at Maturity)
slide33
Finite Population Rate Decrease (er) vs. ZBase calculation with observed fecundity and southern hemisphere age at maturity
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