Age Determination and Validation in Chondrichthyan Fishes Presented by Kara Baca and Sharon Homer-Drummond.

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    14-Dec-2015

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Slide 2 Age Determination and Validation in Chondrichthyan Fishes Presented by Kara Baca and Sharon Homer-Drummond Slide 3 Methodology Age determination process: Collection of hard part samples Collection of hard part samples Preparation of the hard parts Preparation of the hard parts Examination (age reading) Examination (age reading) Assessment of validity and reliability Assessment of validity and reliability Interpretation (modeling growth) Interpretation (modeling growth) Slide 4 Hard parts used Vertebral centra Dorsal fin spines Neural arches Caudal thorns Slide 5 Vertebral Centra Larger, more anterior centra should be used Whole or sectioned Vertebrae should be sectioned sagittally (longitudinally) Vertebrae should be sectioned sagittally (longitudinally) Slide 6 Dorsal Fin Spines Used particularly in dogfish sharks Spines from second dorsal fin are preferred Used whole or longitudinally cut Slide 7 Neural Arches May be useful for species that have poorly calcified vertebral centra Preliminary studies with sixgill sharks Slide 8 Caudal Thorns and Other Structures Caudal thorns used with vertebral centra to determine age in bathyrajid species Evidence for growth bands found in upper jaw of the wobbegong Orectolobus japonicus Serra-Pereria et al., 2005 Slide 9 Preparation of Samples (Centra) Thaw (if frozen) or wash (if preserved in alcohol) Clean excess tissue and separate into individual centra Sectioning typically done with low-speed diamond- bladed saw After mounting sections to slides, sand with wet fine-grit sandpaper to approximately 0.3 to 0.5 mm and air-dry Binocular dissecting microscope is generally used for analysis Slide 10 Age Determination View wide bands (opaque) separated by distinct narrow bands (translucent) Tend to occur in summer (wide) and winter (narrow) Each pair of wide/narrow bands considered to represent an annual growth cycle Validity must be tested Age determination for spines are nearly identical Slide 11 Slide 12 Dorsal fin spines http://journal.nafo.int/35/21-calis.html Slide 13 Banding in Neural Arches Distinct bands in sixgill sharks Potential use in age determination Slide 14 Staining & imagery Imagery & enhancement scanning EM (atypical) steromicroscopy binocular light microscopy X-radiograophy (atypical) X-ray spectrometry Graphite microtopography Staining silver nitrate (McFarlane et al., 2002) cobalt nitrate (Hoenig and Brown, 1998) ammonium sulfide (Hoenig and Brown, 1988) haemotoxylin cedar wood oil, alizarin red, crystal violet, salts (Cu, Fe, & lead) Histology Goldman, 2004 Slide 15 Evaluating Precision Average percent error (APE) May serve as good relative indicator of precision within and between readers May serve as good relative indicator of precision within and between readers However, tells which reader was less variable, not which was better or if either was biased However, tells which reader was less variable, not which was better or if either was biased Goldmans approach to estimating precision: Calculate percent reader agreement (=[No. agreed/No. read] x 100) within and between readers for all samples Calculate percent reader agreement (=[No. agreed/No. read] x 100) within and between readers for all samples Calculate percent agreement plus or minus one year Calculate percent agreement plus or minus one year Calculate percent agreement with individuals divided into appropriate length or disk width groups Calculate percent agreement with individuals divided into appropriate length or disk width groups Test for bias Test for bias Criticism: varies widely among species and ages within a species Criticism: varies widely among species and ages within a species Slide 16 Tests for Bias Age bias plot- graphing one reader vs. the other and referencing equivalence line of the 2 readers (45 line through the origin) Chi-square tests of symmetry, such as Bowkers Evans-Hoenig test Slide 17 Back-Calculation Method for describing the growth history of each individual sampled Numerous methods formulas that follow hard part or body proportion hypothesis are recommended Proportional relationship between animal length or disk width and radius of vertebral centrum or distance from focus to each annulus within a given centrum Proportional relationship between animal length or disk width and radius of vertebral centrum or distance from focus to each annulus within a given centrum Slide 18 Verification & Validation Confirmation of age determination by indeterminate and determinate methods Slide 19 Why validation & verification? Caillet, 1990 Apex Predators website: Sharks are long-lived animals that grow very slowly and do not produce many young. In many parts of the world, sharks are fished commercially, thus, in order to ensure proper management of the stocks, age and growth data must be obtained. With this data, we can determine the longevity of the species as well as maximum age, age at maturity, growth rate, and differences in growth between males and females. The process of evaluating growth zone deposition in fishes can be divided into verification and validation. Verification: conforming an age estimate by comparison with other indeterminate methods Validation: proving the accuracy of age estimates by comparison with a determinate age Slide 20 Some methods of validation Chemical tagging of wild fish Mark-recapture of known-age fish* Bomb carbon dating* Growth ring frequency distinction between absolute age (*) & periodicity distinction between absolute age (*) & periodicity Centrum age analysis Relative marginal increment analysis Some methods of verification Slide 21 Size mode analysis Primarily a verification tool Progression of discrete length modes over time Size modes taken from a random sample of all size classes from a population Size modes taken from a random sample of all size classes from a population Mean or median sizes in age classes assessed by other means (e.g.: age classes predicted by von Bertalanffy growth function applied to physical assessment) Mean or median sizes in age classes assessed by other means (e.g.: age classes predicted by von Bertalanffy growth function applied to physical assessment) Random sample size modes and mean or median sizes at age compared Random sample size modes and mean or median sizes at age compared Coincidence supports assumption of age classes Coincidence supports assumption of age classes Monitor discrete length modes across a given time period at discrete intervals Monitor discrete length modes across a given time period at discrete intervals Slide 22 Tag-recapture Initial in field: Capture Capture Measure Measure Weigh Weigh Tag Tag Release Release Recapture and assess for growth in length and/or weight Compared to von Bertalanffy growth functions, TET, oxytetracycline (OTC) or other methods, based on size changes between tagging and recapture Slide 23 file:///D:/age%20validation/Tetracycline%20or%20OTC_files/age1.jpg Slide 24 Simpfendorder, 2000: dusky sharks Slide 25 Chemical marking, tag-recapture & lab Validation of absolute age focuses on validating temporal periodicity of growth increment formation Tetracycline (TET): standard for marking free-swimming animals Tetracycline (TET): standard for marking free-swimming animals OTC: marks by binding to Ca 2+ & depositing to active calcification sites OTC: marks by binding to Ca 2+ & depositing to active calcification sites 25mg/kg bw IM 25mg/kg bw IM + external tag + external tag highly visible marks in vetebral centra & dorsal fin spines under UV highly visible marks in vetebral centra & dorsal fin spines under UV use body growth & calcification changes to compare time at liberty [release] w/growth band deposition (# rings in vetra centra or spine post-injection = time hacks) use body growth & calcification changes to compare time at liberty [release] w/growth band deposition (# rings in vetra centra or spine post-injection = time hacks) lab or captivity lab or captivity Tag-recapture + marking Tag-recapture + marking tag + OTC followed by recapture tag + OTC followed by recapture tag + TET followed by recapture tag + TET followed by recapture Other tags Other tags Fluorescein (not well-evaluated in elasmo.; 5-10mg/kg bw, higher=mortality) Fluorescein (not well-evaluated in elasmo.; 5-10mg/kg bw, higher=mortality) Calcein (not well-evaluated in elasmo..; 5-10mg/kg bw, higher=mortality) Calcein (not well-evaluated in elasmo..; 5-10mg/kg bw, higher=mortality) Define age & indiv. growth characteristics Combining information from mark w/observed growth changes Slide 26 Tetracycline group Broad spectrum Abs that block bacterial protein synthesis by inhibition of aminoacyl-t-RNA binding to the rRNA A site. TET = tetracycline higher water solubility at pH = 7, than other Abs in same group higher water solubility at pH = 7, than other Abs in same group OTC = oxytetracycline Inject TET or OTC at capture while tagging 25 mg/kg 25 mg/kg absorbed & deposited at growth sites absorbed & deposited at growth sites only mark glows under UV only mark glows under UV pairs > mark = growth over time pairs > mark = growth over time Slide 27 Centrum edge analysis Centrum edge analysis: Compares opacity (width) &/or translucency (density) of centrum edge over time Compares opacity (width) &/or translucency (density) of centrum edge over time measure or grade edge measure or grade edge compare to time of year or season compare to time of year or season detail: analyze Ca 2+ & PO 4 at edge by x-ray or electron microprobe spectrometry detail: analyze Ca 2+ & PO 4 at edge by x-ray or electron microprobe spectrometry not used much yet: not used much yet: recaptured nurse sharks marked with TET (Carrier and Radtke, 1988) recaptured nurse sharks marked with TET (Carrier and Radtke, 1988) 4 ray species in the Irish Sea marked with TET (Gallagher et al., 2004) 4 ray species in the Irish Sea marked with TET (Gallagher et al., 2004) tiger sharks (Winter and Dudley, 2000) tiger sharks (Winter and Dudley, 2000) http://journal.nafo.int/35/10-gallagher.html Winter and Dudley, 2000 Slide 28 Relative marginal increment analysis RMI = MIR (ratio): (VR-R n )/(R n -R n-1 ) Parameters Parameters MIR marginal increment ratio MIR marginal increment ratio VR = vetebral radius VR = vetebral radius R n = distance from center to outer edge of last complete band R n = distance from center to outer edge of last complete band R n-1 = distance from center to outer edge of next-to-last complete band R n-1 = distance from center to outer edge of next-to-last complete band Direct: plot against month to find band formation trend line Direct: plot against month to find band formation trend line Assess seasonal band &/or ring deposition Assess seasonal band &/or ring deposition measure margin (growth) area of centrum from last growth ring to centrum edge measure margin (growth) area of centrum from last growth ring to centrum edge divide by width of last fully formed annulus (none for age 0) divide by width of last fully formed annulus (none for age 0) plot values against month of capture plot values against month of capture determine periodicity of band formation determine periodicity of band formation Poss. combine w/stable isotope analysis Poss. combine w/stable isotope analysis fish work fish work no elasmo. work yet no elasmo. work yet proved viable in other chondrichthyans proved viable in other chondrichthyans Slide 29 Carlson and Baremore, 2004 Slide 30 Neer et al., 2005: Bull shark growth Slide 31 Captive rearing Laboratory or aquaria growth Particularly useful if poor ring formation, calcification, etc. Particularly useful if poor ring formation, calcification, etc. Morphometric data reveals age and growth Morphometric data reveals age and growth Periodicity of growth zone formation in vetebral centra Periodicity of growth zone formation in vetebral centra Difficult to determine true baseline & captivity effects Difficult to determine true baseline & captivity effects www.pac.dfo-mpo.gc.ca Slide 32 Bomb carbon (radiocarbon) aging Tied to global oceanic rise in 14 C following cold war atomic testing Synchronous uptake in marine carbonates Dated marker of calcified structures allowing growth band dating Born < 1956: low Born < 1956: low Born 1956-1965: higher Born 1956-1965: higher Born > 1965: declining Born > 1965: declining Regional identification Validation of annulus formation & absolute age Slide 33 Campana et al., 2002 Slide 34 Slide 35 Current status of studies Caillet, 1995 was last major review 115 publications listed in chapter since then (several not included in chapter that were published late 2004 mid-2005) 115 publications listed in chapter since then (several not included in chapter that were published late 2004 mid-2005) 68 newly studied spp. among those 68 newly studied spp. among those Methods: most studies combine (mult. validation & mult. verification) most use structure calcification most use structure calcification 1 ly vetebral centra (70% of studies reviewed in chap.) 1 ly vetebral centra (70% of studies reviewed in chap.) dorsal spines (7%) dorsal spines (7%) neural arches (1 study) & jaws (1 study) neural arches (1 study) & jaws (1 study) captive growth (9%) captive growth (9%) tag-recapture (7%) tag-recapture (7%) embryonic growth (4%) embryonic growth (4%) precision analyses: several growth parameter values precision analyses: several growth parameter values 1 reviewed methods = MIR or ratio (50%) + centrum edge modal analysis (25 studies, 22 spp.) modal analysis (25 studies, 22 spp.) tag-recapture (20 studies, 19 spp.; many combined w/OTC marking) tag-recapture (20 studies, 19 spp.; many combined w/OTC marking) lab growth (21 studies; 18 of which used OTC marking) lab growth (21 studies; 18 of which used OTC marking) bomb carbon study (Natanson et al., 2002, validated pobeagle growth & indicated shortfin mako growth of 1 ring/yr.) bomb carbon study (Natanson et al., 2002, validated pobeagle growth & indicated shortfin mako growth of 1 ring/yr.) combined w/tag-recapture & OTC combined w/tag-recapture & OTC Combining validation & verification seems to be the most robust means Slide 36 Growth models von Bertalanffy (VBGF): fish growth size at a given point in time depends on anabolism & catabolism size at a given point in time depends on anabolism & catabolism identification of the growth coefficients are dependent on the given study identification of the growth coefficients are dependent on the given study easy population comparisons easy population comparisons fitting allows for fine-tuning fitting allows for fine-tuning problems: problems: small sample size: poor parameter estimation small sample size: poor parameter estimation t 0 (theoretical size) should be replaced by L 0 (length at birth) as 3 rd parameter (more to come) t 0 (theoretical size) should be replac...

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