Radion1etric Ageing of Sharks

Dr G.E. Fenton

FIS HERIE S RESEARCH & DEVELOPMENT UNIVERSITY OF TASMANIA CORPORATIO N

Project No. 94/021 2001 FINALREPORT Radiometric Ageing o{Sharks

Table of Contents

Acknow ledgments ...... 3

1. Non-technical Summary...... 4

2. Background...... 5 2.1 Radiometric analysis ...... 6 2.2 Shark Species Studied ...... 8 a) School shark Galeorhinus galeus ...... 8 b) Spotted Dogfish Squalus acanthias ...... 9 c) Golden Dogfish Centroscymnus crepidater ...... 9 d) Southern Dogfish Centrophorus uyato...... 10

3. Need ...... 11

4. Objectives...... 11

5. Methods ...... 11 5 .1 Collection of shark vertebrae ...... 11 5.2 Dissection and Cleaning vertebrae ...... 12 5.3 Second Dorsal Spine ...... 13 5.4 Radionuclide Analysis ...... 14 5.5 Trace Element Analysis ...... 14

6. Results ...... 14 6.1. Vertebrae morphometrics ...... 14 a) School shark G.galeus ...... 14 b) Spotted Dogfish S.acanthias ...... 15 c) Golden Dogfish C.crepidater ...... 15 d) Southern Dogfish C.uyato ...... 16 6.2. Second Dorsal Spine S.acanthias ...... 16 6.3. Stable element analysis ...... 17

1 FINALREPORT Radiometric Ageing ofSharks

a) Calcium levels ...... 17 b) Strontium levels ...... 18 c) Barium levels...... 19 d) Lead levels ...... 20 6.4. Radioactive Isotopes ...... 21 a) 210pb levels ...... 21 b) 226Ra levels ...... 23 c) 210pb/226Ra Activity ratios...... 24 6.5. Estimation of shark age...... 25

7. Age Estimation Results and Discussion ...... 25

8. Benefits...... 26

9. Further Development...... 30

10. Conclusion...... 31

11. References...... 32

Appendix 1 :Intellectual property arising ...... 37

Appendix 2: Staff...... 37

2 FINAL REPORT Radiometric Ageing ofSharks

Acknowledgements

Thanks are extended to Dr Terry Walker and colleagues at the Marine Science Labs (now MAFRI) Queenscliff for assistance collecting school shark, to Dr John Stevens and colleagues at CSIRO for assistance with collecting shark vertebrae and commenting on a draft of this report. Thanks are also extended to Matt Healey for his enthusiastic assistance measuring vertebrae and spines, particularly after I had resigned from the University to take up a position working for the Tasmanian Department of Primary Industries, Water and Environment. The analytical skills of Rob Chisari, from the Australian Nuclear Science and Technology Organisation are gratefully acknowledged forconducting the radiometric analyses. The support of Laura Denholm from the Research Office and to Prof. Craig Johnson and Barry Rumbold from the School of Zoology University of Tasmania was appreciated during a rather complicated process of completing this research after leaving the University. Finally thanks to the support and patience of my family during the write up of this project given it was entirely an "after-work and kids-bedtime" exercise.

3 FINAL REPORT Radiometric Ageing ofSharks

1. Non-technical Summary Determining the age of sharks 1s difficult. A reliable independent method of validating age estimates is needed, apart from relying on tag return data. The success of radiometric analysis for bony fish overseas and in Australia suggested that it would be worth trying the method on sharks. Four species were chosen for this study, school shark Galeorhinus galeus, white­ spotted dogfish Squalus acanthias, and two deepwater sharks golden dogfish Centroscymnus crepidater and the southern dogfish Centrophorus uyato. The results of the study were quite different from previous radiometric analyses of fish otoliths. Age estimates have been made using the in-growth of 210Pb. The age estimates for G.galeus range from 22 to 55 years. These age estimates are remarkably similar to the known tag return ages for this species, but are very different from the ages estimated by the alizarin red method used on vertebrae from each of the individuals radiometrically analysed here. The alizarin red method gave ages up to a maximum of 11 years. The problems with the alizarin red method were already known, and this was part of the reason why the radiometric method was applied to school sharks. The age estimates for S.acanthias using the radiometric method range from 40 to 78 years. These ages do not match the age estimates from counting bands in sections of the second dorsal spine, where the maximum age recorded here was 23 years. However this species has been widely reported to be long-lived, in the order of 70 years. The ages estimated for C.crepidater ranged from 26 to 43 years, this small range in ages reflecting the small size range of sharks available foranalysis. This is the firstestimate of age for this species. The radiometric age method estimated the age of C.uyato ranging from 34 to 46 years. Again the smaller size range of individuals was reflected in similar ages. This is also the first estimate of age for this species.

4 FINAL REPORT Radiometric Ageing ofSharks

The technique was also applied to a range of teleost and other shark species where 210Pb values were available. The results of this analysis also indicate the validity of this method for age determination. In summary the project has been successful in fulfilling the objectives of the study, and importantly the method looks very promising to offer an alternate method of ageing and a validation tool. The results of this study point to further development of this method for sharks, including analysing vertebrae from tag­ return individuals which have been at liberty for many years.

2. Background Resource assessment is important for management of shark fisheries in Australia. One of the key requirements for this assessment is accurate estimation of age. However accurate age determination remains difficultfor sharks. There are many techniques that have been used for ageing sharks, but verification/validation of the ages still remains difficult. Shark ageing methods have generally involved counting opaque and translucent bands present in vertebrae and finspines. However, few studies have attempted to determine the periodicity of these bands. A review by Cailliet (1990) found that age had been validated in only 6 species. Many studies have however, at least partially verified their age estimates. Where verification is defined as the process of confirming an age estimated by comparison with other indeterminate methods and validation is proving the ages are true by comparison with a determinate method and this must be conducted for all size classes. Cailliet (1990) listed 7 methods that have been used to estimate age and verify the periodicity of band formation in elasmobranchs: 1. back calculation and calculation of growth model parameters (neither qualify as verification); 2. size frequency analysis 3. centrum or spine edge dimensions, histological characteristics, and/or elemental analysis;

5 FINALREPORT Radiometric Ageing ofSharks

4. radiometric dating 5. laboratory growth studies 6. tag recapture studies fromthe field; and 7. tetracycline marking both in the field and laboratory.

The main methods of verification/validation have included using tetracycline and tag returns. However, both these methods require long time periods before recapture to provide usefulage information.Little has changed in the last 10 years in this area, although many more studies of shark age have been published.

2. 1 Radiometric analysis Radiometric analysis is an independent ageing technique that measures the natural level of radioactive isotopes e.g. 210Pb and 226 Ra in calcified structures such as otoliths and vertebrae. The radiometric technique is based on the factthat radioisotopes decay at known rates and thereforeprovide natural "clocks" by which age can be determined. Natural levels of the radioisotopes 210Pb (22.3 year half-life) and 226Ra (1620 year half-life) can be used for ageing fish. These isotopes occur naturally in seawater and are incorporated unequally (i.e. in disequilibrium) into the otoliths of fish. 226Ra is taken up as a chemical analogue of calcium and thereafter decays into 210Pb. It is the increasing level of 210Pb relative to 226Ra that provides a measure of time elapsed since incorporation and hence fishage. It is this decay of 226Ra into 210Pb that has been used successfully to age a range of teleost fishin recent years. Radiometric analysis has been successfully applied to several species of fish, including the splitnose rockfishSebastes diploproa (Bennett et al., 1982), Atlantic redfish Sebastes mentella (Campana et al., 1990), flying fish Hirundichthys a/finis and silver hake Merluccius bilinearis (Smith et al., 1991), Pacificgrenadier Coryphaenoides acrolepis and tarpon Megalops atlanticus (Burton et al. 1999). The technique has already proven its usefulness in Australia forage determination of several deep-sea commercial fin-fish species in recent years e.g.

6 FINAL REPORT Radiometric Ageing o(Sharks orange roughy Hoplostethus atlanticus (Fenton et al., 1990 and Smith et al., 1995), warty oreo Allocyttus verrucosus (Stewart et al. 1995), blue grenadier (Fenton and Short, 1995) and for used for spiky, smooth and black oreos (Fenton, 1996). However the technique has not been without its critics. West and Gauldie (1994) raised the likelihood of escape of 222Rn from otoliths as 226Ra decays into 210Pb (See Fig.I). However a study by Whitehead and Ditchburn (1994) has experimentally tested whether 222Rn is lost fromorange roughy otoliths or not. Their work found that no radon escapes from otoliths, supporting the long-lived estimates for orange roughy using the radiometric technique. Noting that if radon did escape that 210Pb values would be lower (i.e. causing a break in the decay chain see Fig. 1) and consequently ages would be underestimated. While sharks are quite different from bony fishwith their cartilaginous skeletons, the vertebrae of many shark families are well calcified. Clement (1992) conducted a detailed review of the calcification of chondrichthyans. His work importantly showed no evidence of resorption of the skeleton occurring. This 226 calcification ensures that the useful natural radionuclides Ra and 210Pb are incorporated into the vertebrae as they are formed. A preliminary study by Welden (1984) and Welden et al., 1987 in California measured 210Pb in the inner and outer peripheral bands of shark vertebrae to age four species of shark, Pacific angel shark Squatina californica , white shark Carcharodon carcharias, leopard shark Triahis semifasciata and common thresher shark Alopias vulpinus. The results of their study had mixed success with age estimates fo1· the PacificAngel and white sharks comparable to those made using other methods, however their work was not taken further. Interestingly they did not routinely measure 226Ra, the isotopic parent of 210Pb and yet by measuring 226Ra could potentially enhance the interpretation of the analyses. However, they did 22 measure 6Ra in the white shark. Since their study, major advances in radiometric methodology have occurred with respect to bony fish and this increased knowledge should significantly enhance the prospects of success for ageing sharks.

7 Uranium Decay Series

2 3au 9 4.49x10 y JJ 23 4Th 24.1 d JJ 234 Pa 1.18 m JJ 230 Th 4 7.52x10 y JJ 22 sRa 1602 y JJ 222 Rn 3.825 d JJ 21 21 ap0 aAt 3.05 m 2s JJ 21 21 214 4pb 4Bi Pa 4 26.8 m 19.7 m 1.64x10- s JJ 21 210 210 21o 0TI pb Bi p0 1.32 m 22.3 y 5.02 d 138.3 d JJ 2 6 0 pb STABLE

Fig 1. The Uranium Decay Series showing all isotopes in the radioactive decay series. Note the position of 226Ra and 210Pb and 210Po. FINAL REPORT Radiometric Ageing ofSharks

There are several key areas in which the present study has been designed to improve on earlier work on sharks: I. analysing 226Ra in the vertebrae; 2. analysing stable lead, barium, calcium and strontium in the samples to cross check uptake patterns; 3. analysing more samples of each species, including juveniles when possible.

Perhaps the most obvious improvement would be to age "known-age" sharks. Although a few vertebrae were available fromtag-returns, it was critical to assess whether effectiveness and applicability of the radiometric method prior to trying such scientifically valuable samples, given this technique is destructive.

2.2 Shark Species Studied In this study fourspecies of sharks were examined. A summary of the biological informationknown about these species is given here. a) School shark Galeorhinus galeus (Linneaus, 1758) FISH cooE oo 01100s School shark Galeorhinus galeus (Family Triakidae- the hound sharks) have been fished commercially in southern Australia since the 1920's. The species inhabits temperate and sub-tropical waters of the Southern Hemisphere, Eastern North Pacificand eastern North Atlantic Oceans (Compagno 1988). It is common in New Zealand and southern Australia from Moreton Bay in Queensland to Perth in Western Australia including Lord Howe Island and Tasmania (Last and Stevens, 1994). It is a demersal species found on the continental and insular shelves. It ranges in depth from shallow coastal bays to 550m. School shark are known to make long breeding migrations. Tagging studies have revealed individuals covering up to 2500km in the north-east Atlantic and locally 1400km during migrations. It is oviviparous giving birth to litters of 15-43 pups in December- January in southern Australia. The young are born at around 30cm length. Females mature around 130cm length, which is thought to correspond to an age of 8-10 years. Males maturing at around 120cm. School shark can reach 175cm in length. However age

8 FINAL REPORT Radiometric Ageing ofSharks estimates using alizarin staining of whole vertebrae are known to be inaccurate for larger individuals (Moulton et al., 1992). Tagged individuals have revealed long life spans. One individual was at liberty for over 35 years (Anon. 1991), but only 14 bands were found on the vertebrae of this shark using the alizarin method. The maximum age recorded from a tag return is 55 years (Moulton et al. 1989, 1992). The diet of school sharks is composed largely of fish and cephalopods (Last and Stevens, 1994). b) White-spotted dogfish Squalus acanthias Linnaeus, 1758 FISH coDE oo 02000a S.acanthias is widely distributed in the North Atlantic and Pacific Oceans, and is found around the southern tips of South America, Africa, and New Zealand. It is common in Tasmanian and Victorian waters and is also recorded from the Great Australian Bight. It is considered to be one of the most abundant of all living sharks and is commercially very important particularly in Europe (Last and Stevens, 1994). While largely considered to be an inshore species it has been found at depths up to 900m (Compagno, 1984). In Australia it breeds in inshore bays and estuaries, giving birth to up to 20 young. The young are born at around 22cm, males mature at about 59cm and adults grow to around 100cm in Australian waters, although individuals up to 160cm have been caught in the Eastern North Pacific Ocean. Gestation is reported to last 18-24 months, making it among the longest known for any shark. Reports to date show the species to be very long lived with maximum ages of up to 70 years. reported. Estimates of maturity have ranged between 10-35 years (Saunders and McFarlane (1993). The diet of S.acanthias consists largely of small fish and crustaceans although molluscs including small scallops are also eaten (Last and Stevens, 1994). c) Golden dogfish Centroscymnus crepidater (Bocage and Capello, 1864) FISH CODE 00 020012 C.crepidater is known from the Eastern Atlantic from Iceland to southern Africa and in the Indian Ocean from India and the Aldadra Islands, in the eastern Pacific from northern Chile and the western Pacific from New Zealand and all of southern Australia (Last and Stevens, 1994). It is found on or near the bottom on

9 FINALREPORT Radiometric Ageing ofSharks continental and insular slopes in depths ranging from 270-1300m. It is a fairly common species in southern Australia generally found in depths from 780-ll00m. It is taken as bycatch in the orange roughy fishery, it is not edible due to high mercury levels in the flesh however, the liver oil is rich in squalene (Nichols et al. 1998; Wetherbee and Nichols, 2000). The biology is not well known although females appear to breed throughout the year, it is ovoviviparous with 4-8 pups per litter. The young are born at 30-35cm and adults grow to a length of 105cm. Males are mature at around 60cm and females around 80cm Australia (Last and Stevens, 1994). Its diet is reported to consist largely of fish and cephalopods. d) Southern dogfish Centrophorus uyato (Rafinesque, 1810) FISH cooE oo 020011 The distribution of C.uyato is reported by Last and Stevens (1994) to include the Gulf of Mexico, Eastern Atlantic from Portugal to Namibai including the Mediterranean, the Indian Ocean from southern Mozambique and possibly India, and the western Pacific from Taiwan. In Australia it has been found from Albany to Geraldton in Western Australia and from Fowlers Bay in South Australia around to Port Stephens New South Wales including Tasmanian waters. In Australia it is mainly found in waters 400 to 650m of depth although it is known to be demersal on continental shelves and slopes ranging in depth from 50 to 1400m. The biology of the species is not well known. It is ovoviviparous, producing one pup. The pups are born at about 35cm length and grow to a length of 100cm. The size at maturity is not known although males are reported to be mature at 80cm. Anterior to each dorsal fin is a dorsal spine.

The diet of C. uyato is known to consist mainly of fish and cephalopods (Last and Stevens, 1994).

3. Need Sharks are of significant commercial importance in Australia, with three major fisheries defined: the Southern Shark Fishery, the Northern Shark Fishery

10 FINAL REPORT Radiometric Ageing ofSharks and the South West Shark Fishery. A number of shark species are harvested in Australia mostly forhuman consumption but also for a number of other shark products including liver oils and shark fins. Over recent years there has been developing interest in harvesting deepwater sharks for squalene, and other liver oils, as a bycatch of other fisheries (Nichols et al. 1998, Wetherbee and Nichols, 2000). Thereforedevelopment of a method capable of providing accurate age estimates is critical formanagement of shark fisheries. The commercial value of the southern shark Fishery (gummy and school sharks) in 1991 was estimated to be $15M (Joll, 1993). The value in 1998 was $10.8 M with the catch composed of 579 tonnes of school shark and 1523 tonnes of gummy shark (Caton and McLaughlin, 2000). Given the importance of the shark resources in Australia, it is critical that accurate stock assessments are available formanagement of the fisheries. Accurate age estimation is one of the key requirements for this assessment. Shark ages are difficult to verify or validate. Furthermore no age estimates are available forany deepwater dogfishin Australia. Therefore the fact that radiometric analysis maybe a solution to this problem is worth investigation.

4. Objectives The objectives stated in the original proposal were: • To use radiometric analysis for validating shark ages. • To age school sharks • To age deepwater shark species

5. Methods

5. 1 Collection of Shark vertebrae Vertebrae fromschool sharks G.galeus were taken fromthe same individuals that had been previously aged using the alizarin red method of Moulton et al. (1982). These vertebrae were made available by the Marine Science Laboratories,

11 FINAL REPORT Radiometric Ageing ofSharks

Queenscliff, Victoria. Vertebrae from tag-return sharks were not used given the destructive nature of the radiometric analysis and uncertain nature of applying this technique in this study. Vertebrae of white-spotted dogfish Squalus acanthias were collected locally, the largest individuals retained for radio ageing purposes. Vertebrae of C.crepidater were collected on cruises of the CSIRO research vessel Southern Surveyor south of Tasmania as part of a separate research project. Some additional deep-sea shark samples were purchased fromlocal orange roughy fisherman. Specimens of C.uyato were purchased from Victorian fisherman. C. uyato were packed frozen and shipped to the University of Tasmania for dissection.

5.2 Dissection and Cleaning vertebrae A standard approach for selecting vertebrae was maintained for S.acanthias, C.crepidater and C.uyato. The samples were taken starting at the sixteenth vertebrae from the base of the cranium. All vertebrae posterior to this point were included until the combined cleaned weight of the vertebrae was in excess of 1 gram. The vertebrae of G.galeus had all been removed from the region beneath the dorsal fin (Walker pers.comm.). All vertebrae were mechanically cleaned of as much connective tissue as possible. Individual vertebrae were separated and excess hyaline cartilage removed to reduce the immersion time in the sodium hypochlorite. Vertebrae were cleaned using a solution of 20g/L of sodium hypochlorite. The vertebrae from each individual were placed in separate beakers containing 200ml of solution. The solution was replaced for each group as the potency of the solution decreased markedly throughout the process. The cleaning process took between 1 and 2 hours to complete. After removal from the solution the vertebrae were washed in distilled water for 20-30min. The vertebrae were then air dried before the physical dimensions length, diameter and weight of each individual vertebrae were measured. Weight was measured using a micro-balance, vertebrae length and diameter were measured using vernier calipers.

12 FINAL REPORT Radiometric Ageing o(Sharks

5.3 Second Dorsal Spine A total of 48 individuals of S.acanthias were used for estimating the age of members of this species. These included 31 males and 17 females with total lengths ranging from 54-83.lcm. As recommended by McFarlane and Beamish (1987) , the age of individuals was estimated from annuli formed in the second dorsal spine. Each spine was removed and cleaned of excess material to exposed the enamel coating along the entire length of the spine. This was easily achieved by immersing the spines in water for up to 48 hours. Annuli were counted under a dissecting microscope using an exte1·nal light source. As recommended by McFarlane and Beamish (1987), annuli were counted from the base of the enamel to the No Wear Point (point at which annuli become ill defined due to wear). All annuli were counted irrespective of clarity or distance apart. The diameter of the spine at the No Wear Point (NWP) was measured for correcting the estimated ages due to wear. Using this, a correction factor may be calculated using the spine diameter/age formula (1) as derived by Scott (1992). However, it has been shown that if the diameter at the NWP is less than 1.78mm then the worn section of the spine is less than 1 year old (Scott, 1992). If this was the case then the estimated age was not corrected, with the number of annuli taken as the age of the individual.

Correction (yrs) = l.3644x10 [0.26704xNWP(mm)] (1) All spines were examined three times. The age of those individuals with 10 bands or less was excepted if two counts agreed to within one. For those spines with more than 10 annuli, ages were only excepted if two counts agreed to within two. All other spines were deemed 'unreadable'. The estimated ages of individuals were used to derived a Von Bertalanffy Growth Formula (VBGF), providing estimates of the growth rate and maximum attainable size of members of this species. The VBGF was estimated using the non­ linear Quasi-Newton Estimation method provided by SYSTAT 5.2.

13 FINALREPORT Radiometric Ageing ofSharks

5.4 Radionuclide Analysis Vertebrae from several individuals of each species were analysed. Radiometric analysis was conducted on samples that were I-year post-collection, to 2 2 2 allow for 10Pb and 10Po to reach radioactive equilibrium. The isotopes 10Pb (via its 2 alpha-emitting grand-daughter 10Po) and 226Ra were analysed by high resolution alpha-spectrometry. The analytical method used here followed the method described in Fenton et al. (1991). Polonium-210 was assumed to be in equilibrium 2 with 10Pb in all samples, since all samples were collected more than 1 year before analysis. Trials using a non-destructive gamma analysis technique at ANSTO did not prove successful thereforeall analyses were conducted using the proven alpha­ spectrometry method. All radiometric analyses were conducted at the Low Level Radiochemistry Laboratory ANSTO.

5.5 Trace Element Analysis Ion coupled plasma atomic absorption spectrometry (ICP-AES) of calcium and strontium and ion coupled plasma mass spectrometry (ICP-MS) of lead and barium was conducted on each vertebral sample. These elements were analysed to establish the pattern of calcification and incorporation of the radioactive elements via their stable counterparts lead and barium (analogous to radium).

6. Results

6. 1 Vertebrae morphometrics a) School shark G.galeus Measurements were made of up to 6 vertebrae from 60 individuals. Vertebral length, diameter and weight were recorded for each vertebrae. The relationship between vertebral length and fish length is plotted in Fig. 2. This graph shows a strong linear relationship (r2= 0.802) between vertebrae length and fish length. A similar very strong linear relationship was present between vertebrae diameter and fish length (Fig. 3, r2= 0.936). An exponential relationship (r2 =0.936) was observed

14 15 -r------,

-E -E 10 .c -C, C -2:! Cl) 5 � .c ,@ >Cl)

0 500 1000 1500 2000

Total length (mm) 2 y = 0.006x - 0.249 r = 0.802

Fig.2 G.galeus relationship between vertebrae length and fish length.

-E -E .s"- Cl) E CU "'C Cl) � .c ,@ >Cl)

0 500 1000 1500 2000

Total length (mm) 2 y = 0.009x - 0.927 r = 0.936

Fig.3 G.galeus relationship between vertebrae diameter and fishlength. -0, 1.5

.c- 0, Q)

Q) .c ,@ 0.5 >Q)

0 0 500 1000 1500 2000

Total length (mm) y = 0.004 * 10 0,00lx r2 = 0.936

Fig.4 G.galeus relationship between vertebrae weight and fish length.

12

10

E E 8 .c -0, 6 Q)

Q) 4 .c ,@ 2 >Q)

0 0 25 50 75 100

Fish Length (cm) y = 0.122x - 2.986 r 2 = 0.833

Fig.5 S.acanthais relationship between vertebrae length and fish length. FINAL REPORT Radiometric Ageing o{Sharks fish length (Fig. 3, r2= 0.936). An exponential relationship (r2 =0.936) was observed between vertebral weight and fish length (Fig. 4). In all cases strong relationships were observed between the vertebral dimensions and fish length.

b) Spotted dogfish S.acanthias The size range selected for analysis consists almost entirely of large, mature specimens. Small individuals were not found at any sites sampled. All samples analysed were collected from the D'Entrecasteaux Channel. Although pups from pregnant females were available for radiometric analysis, the calcification of these vertebrae was so low that the collection of sufficient material to analyse radiometrically was unrealistic. The risk of contamination by adhering organic material was too great. A strong linear relationship was present between fish length and both the vertebrae length (r2 =0.833) and diameter (r2=0.889) of Squalus acanthias (Fig. 5 & 6). An exponential relationship was observed between vertebrae weight and fish length (Fig. 7, r2=0.942). c) Golden dogfish C.crepidater The availability of this species was problematic during the project. Only 7 females were available for analysis, however this did include several large mature females. The dimensions of the vertebrae of C.crepidater showed a similar relationship to total body length compared to that seen in G.galeus and S. acanthias. Both the vertebrae length (r2 =0.829) and diameter (r2=0.612) exhibited a linear relationship to body length (Figs.8 & 9). The relationship between vertebrae weight and fish length (Fig. 10) also showed a linear relationship (r2=0. 718). This is different to the strongly exponential curve seen in both G.galeus and S. acanthias, however this is probably due to the restricted size range of the sharks available for this species.

15 10 -E E -... 7.5 Q) Q) E 5 -C� Q)

.c 2.5 � >Q)

0 25 50 75 100

Fish Length (cm) y = 0.118x - 1.996 r 2 = 0.889

Fig.6 S.acanthias relationship between vertebrae diameter and fish length.

- 0.3 -C') .c:- C') ::Q) 0.2 Q) .cl! 0.1 � >Q)

0 25 50 75 100

Fish Length (cm) y = 0.000 * 10 o.o2sx r2 = 0.942

Fig.7 S.acanthias relationship between vertebrae weight and fish length. -E E .c- -C, C: � Cl) � .c ,@ >Cl)

50 60 70 80 90 100 Fish length (cm) y = 0.143x- 5.506 r 2 = 0.829

Fig.8 C.crepidater relationship between vertebrae length and fish length.

-E -...E s Cl) E "'Cl-� Cl) � .c ,@ >Cl)

50 60 70 80 90 100 Fish length (cm) y = 0.lllx-1.729 r 2 = 0.612

Fig.9 C.crepidater relationship between vertebrae diameter and fish length. 0.3 -C) .c- C) 'ci) 0.2 3: Cl) � .c Cl) t:: 0.1 >Cl)

50 60 70 80 90 100

Fish length (cm) y = 0.008x - 0.571 r 2 = 0.718

Fig.10 C.crepidater relationship between vertebrae weight and fish length.

8--.------,

6 -E E -.c C) C 4 � Cl) .c 2 If � >Cl)

0 20 40 60 80 100

Fish length (cm) y = O.lOlx - 2.457 r 2 = 0.695

Fig.11 C.uyato relationship between vertebrae length and fishlength. FINAL REPORT Radiometric Ageing ofSharks d) Southern dogfish C.uyato Vertebrae from 11 individuals of C. uyato were removed. These included mature females with a size range of 58.6-80.9cm. Despite attempts to obtain some juveniles of C. uyato none were found. As with the previous species, this range encompasses large females only. Although the availability of C. uyato was lower than expected, the range and number of females processed was sufficient for analysis. Both vertebrae length and diameter showed a linear relationship with fish length (Figs.II & 12) with r2= 0.695 and r2=0.823 respectively. The relationship between vertebrae weight and fish length (Fig. 13) showed a strong exponential curve r2= 0.894.

In summary the dimensions of vertebrae in all four species showed similar relationships to fish length. This is not surprising given the fundamental structure of the vertebrae in determining fish length. However for age determination the variation in dimensions along the length of the vertebral column is obvious and thereforestandardising the position of vertebrae used forageing is important.

6.2. Second Dorsal Spine S.acanthias Annuli counts from 29 spines, out of the original 48, were accepted as readable. These represented total lengths ranging from 54-82cm and estimated ages ranging from 10-23 yrs, assuming one band per year was formed. The growth rate (k) was estimated to be 0.098 and the maximum attainable length (L) was estimated to 85.228 cm (r2=0.991, Fig.14). The adjusted standard errors and 95% confidence limitsare shown in Table 1.

Table 1. S. acanthias: intrinsic growth and maximum length from the VBGF derived from estimated ages from the second dorsal spine.

Parameter Estimate A.S.E. Lower <95%> Upper L 85.228 6.487 71.895 98.562 k 0.098 0.017 0.063 0.132

16 6 -E -...E .s(l) 4 E C'CI "'C (l) 2 .ce � >(l) o------20 40 60 80 100

Fish length (cm) y = 0.090x - 0.477 r 2 = 0.823

Fig.12 C.uyato relationship between vertebrae diameter and fishlength.

0.06 -C) .c- C) (l) 0.04 3: (l) .ce � 0.02 >(l)

0 25 50 75 100 Fish length (cm) y = 0.000 * 10 °-027x r2 = 0.849

Fig.13 C. uyato relationship between vertebrae weight and fish length. FINAL REPORT Radiometric Ageing ofSharks

Total fish length (cm) =85.228x(I-e[-0.098xAge(yrs)J)

100-r------,

80 0 - 0 E o o � <> .c 60 � � -0, /t

40 0

0 20

0-t---...,.----.,.-----,---.,..---....----.-----1 0 5 10 15 20 25 30 35 Estimated age (yrs )

Fig.14 S. acanthias age estimates derived from the second dorsal spine.

6.3 Stable element analysis a) Calcium levels The calcium levels present in the vertebrae of the four species showed quite different relationships. Although sharks have a cartilaginous skeleton the vertebrae are calcified. The extent of calcification varies between species and was quite different in the 4 species. The calcium content for all species is summarised in Table 2 in all cases the results are corrected for the sample mass.

School shark G.galeus showed a strong linear relationship (r2 = 0.650) between fish length and the calcium content of the vertebrae (Fig. 15). This could be explained by the need for greater structural support with increasing fish length. However, the situation was differentfor the white-spotted dogfish S.acanthias

17 FINAL REPORT Radiometric Ageing ofSharks where no relationship was evident (Fig. 16). There appears to be significant variation in the amount of calcification present forsimilar sized individuals. No relationship between shark length and calcium content was present in C.crepidater (Fig. 17). Nor was there any relationship between calcium content of the vertebrae and fish length for C.uyato (Fig.18). In summary calcification does not appear to relate to fish length in any consistent pattern. b) Strontium levels School shark G.galeus showed a positive linear relationship (r2 = 0.0570) between strontium level in the vertebrae and fish length (Fig. 19). That is, the levels of strontium increased with increasing fish length. This mirrored the calcium values in G.galeus. The situation was much weaker for white-spotted dogfish S.acanthias with only a very weak positive linear relationship (r2 = 0.152) between strontium levels and fish length (Fig.20), this pattern was similar to that seen for calcium incorporation in this species. A weak positive linear relationship (r2 = 0.110) was evident for C.crepidater forstrontium levels in the vertebrae (Fig. 21). This was the same pattern seen for calcium in this species. Whereas for C.uyato there was no linear relationship evident for strontium content of the vertebrae (Fig.22). The pattern mimicking the one seen for calcium in this species. In summary, there was a positive linear relationship forthree species, G.galeus S.acanthias and C.crepidater. The fourth species, C.uyato showed no relationship. Not surprisingly the pattern of incorporation of strontium is similar to the incorporation pattern observed for calcium in each species. Plotting the strontium to calcium ratio against fish length for all species there is an interesting pattern observed (Table 2 and Fig. 23). The Sr/Ca ratio for G.galeus was quite consistent forthe species despite fish length with a mean value of 0.0046 ± 0.0003. However, while the smaller S.acanthias all had similar Sr/Ca values the

18 3000 ------

2500

2000 c. c. CU 1500

1000

D 500 80 100 120 140 160 180

Fish length cm 2 y = 18.41 lx - 520.575 r = 0.650

Fig.15 G.galeus relationship between calcium in the vertebrae and fish length.

3000 ------,

D D

2500 - D E c. D c. CU (.) D D 2000 -

1500 __,___ ..,.,----,-, ----. ---.,----1 50 60 70 80 90 100 Fish length cm

Fig.16 S.acanthias relationship between calcium in the vertebrae and fish length. 3000 --.------,

2500 - 0 0

2000 - 0 0 0 c. c. CU 1500 -

1000 -

500 -t----,---,---,---,------1 50 60 70 80 90 100 Fish length cm

Fig.17 C.crepidater relationship between calcium in the vertebrae and fish length.

3000 ------0 0 0 D 2500 - 0

2000 -

§_ 1500 - c. CU O 1000 - 0 0 500 - 0

0 -t---,---,---,--....,-- ...,---1 55 60 65 70 75 80 85 Fish length cm

Fig.18 C. uyato relationship between calcium in the vertebrae and fish length. 10

E c. 7.5 c. en

5

D 2.5 -+---...----...------4 80 100 120 140 160 180 Fish length cm

2 y = 0.074x - 1.026 r = 0.570

Fig.19 G.galeus relationship between strontium levels and fishlength.

13

11 E c. c. D en 9 D

7-+------4 60 70 80 90 100

Fish length cm 2 y = 0.037x+8.230 r = 0.152

Fig.20 S.acanthias relationship between strontium in the vertebrae and fish length. 15 ------,

D

10

a. a. (/)...

0------50 60 70 80 90 100 Fish length cm y = 0.090x+3.331 r 2 = 0.110

Fig.21 C.crepidater relationship between strontium in the vertebrae and fish length.

15 D D D D D 10 -

a. a. (/) 5 - D D

D

0 I I I I I 55 60 65 70 75 80 85 Fish length cm

Fig.22 C. uyato relationship between strontium levels and fish length. 0.006 - •

-� • • G.galeus 0.004 - ... �- 0 S.acanthias c,:s

C.crepidater U) •

0.002 - 8. C.uyato

0 -+-----.,-----,.,-----, -----1 0 50 100 150 200

Fish length cm

Fig.23 Relationship between Sr/Ca and fish length in all 4 species of shark. Table 2. Stable element analysis for the four species of sharks.

Species Fish Ca Sr ppm Pb ppb Ba ppb Pb/Ba Sr/Ca Length ppm TL (cm)

G.ga/eus 143.2 1909 8.69 0.60 37.29 0.0160 0.0046 G.galeus 161.9 2253 10.22 3.93 42.04 0.0935 0.0045 G.galeus 112.6 2130 9.69 1.28 40.58 0.0315 0.0046 G.galeus 150 2685 11.99 4.79 55.94 0.0857 0.0045 G.galeus 150 2239 10.03 3.30 42.72 0.0772 0.0045 G.galeus 88.8 609 2.87 1.64 18.02 0.0909 0.0047 G.galeus 95.6 1551 8.12 4.19 22.36 0.1875 0.0052

S.acanthias 61.2 2044 9.23 4.02 121.27 0.0331 0.0045 S.acanthias 69 2697 11.99 12.15 53.45 0.2273 0.0044 S.acanthias 91 2032 10.95 20.95 147.30 0.1422 0.0054 S.acanthias 63 2348 10.78 26.78 52.27 0.5123 0.0046 S.acanthias 73.5 2694 11.97 65.66 56.97 1.1525 0.0044 S.acanthias 65 2274 10.25 62.59 47.96 1.3052 0.0045

C.crepidater 86.4 1783 10.68 1.12 70.70 0.0158 0.0060 C.crepidater 81.4 1971 9.59 0.00 48.40 0.0000 0.0049 C.crepidater 93.6 2480 13.04 2.26 107.87 0.0210 0.0053 C.crepidater 81.4 2274 12.41 1.11 78.81 0.0141 0.0055 C.crepidater 90.6 1952 10.12 0.00 52.02 0.0000 0.0052

C.uyato 65.6 2789 12.90 1.09 89.95 0.0121 0.0046 C.uyato 58.6 2680 13.45 10.77 44.44 0.2424 0.0050 C.uyato 80.9 2662 11.71 0.49 76.17 0.0065 0.0044 C.uyato 61.9 840 4.12 1.83 15.57 0.1176 0.0049 C.uyato 77.1 2649 11.26 0.00 102.96 0.0000 0.0043 C.uyato 65.9 344 1.61 0.86 8.62 0.1000 0.0047 C.uyato 69.9 2385 10.60 0.69 56.92 0.0121 0.0044 C.uyato 59.2 791 3.82 2.86 8.57 0.3333 0.0048 FINAL REPORT Radiometric Ageing ofSharks largest individual did have a higher value (0.0054), but the mean for the species was 0.0046±0.0004. C.crepidater had the greatest range in values, ranging from 0.0049 to 0.0060, with a mean value of 0.0054±0.0004. The Sr/Ca ratio for C.uyato showed a trend of decreasing with increasing fish length from 0.0054 to 0.0043 for sharks 58.6 and 77.1 cm respectively, with a mean value of 0.0046±0.0003 forthe species. Although during the early 1980's considerable hope was placed in a relationship between temperature and Sr/Ca ratios in fishotoliths (Radtke and Targett 1984). Later work by Kalish (1989a,b) experimentally showed that the relationship was not as simple as it initially seemed, although a slight temperature signal was seen. However Kalish (1989a,b) did suggest the range of Sr/Ca values seen in different organisms may give some insight into the calcification process, and indeed growth due to the relationship with protein growth in otoliths. c) Barium levels Barium is valuable to analyse because it is a close chemical analogue of the radioactive element radium. Values of barium may give an indication of the type of uptake patterns for the radioactive counterpart radium. In the case of school shark G.galeus the values of barium ranged from 18.02 to 55.94 ppb with a strong positive linear relationship (r2 = 0.682) present between the barium levels in the vertebrae and fish length ((Table 2, Fig. 24). That is, the longer the shark the more barium was present in the vertebrae. However, no relationship was evident for the white spotted dogfish S.acanthias (Fig. 25) and only a weak linear relationship (r2 = 0.246) for C.crepidater, with a large range of values of barium present (Fig. 26). The barium values ranged from 47.96 to 147.3 ppb for S.acanthias and from 48.4 to 107.9 ppb for C.crepidater. Barium values ranged from 8.618 to 103 ppb for C.uyato with a positive linear relationship (r2 = 0.466) present showing an increase in barium with increasing fish length (Fig. 27), similar to the pattern observed in G.galeus.

19 60 -.------, D

50

40 .c a. a. CU 30 DJ

20

10 -+----.---....---.-----.----1 80 100 120 140 160 180

Fish length cm y = 0.364x - 11.101 r 2 = 0.682

Fig.24 G.galeus relationship between barium in the vertebrae and fish length.

150 LJ

125 - D

100 - .c a. a. CU DJ 75 -

D O D 50 - D

25 I I 60 70 80 90 100 Fish length cm

Fig.25 S.acanthias relationship between barium in the vertebrae and fish length. 125 ------,

D 100

75 .c a. a. C'G 50 III

25

0 -i------....------4 50 60 70 80 90 100 Fish length cm y = 2.174x- 116.902 r 2 = 0.246

Fig.26 C.crepidater relationship between barium in the vertebrae and fish length.

125 ------,

100

75 .c a. a. C'G 50 III

25

D D 0 -i----.------4 55 60 65 70 75 80 85 Fish length cm y= 3.137x-161.000 r 2= 0.466

Fig.27 C.uyato relationship between barium in the vertebrae and fishlength. FINAL REPORT Radiometric Ageing ofSharks

In summary, three species G.galeus, C.crepidater and C.uyato showed a linear relationship between barium content in the vertebrae and fishlength, but S.acanthias did not. In drawing conclusions about the pattern of barium incorporation in these shark species it is important to note that the levels observed here are an order of magnitude lower than that observed in fish otoliths. In fish otoliths values are reported in part per million (ppm) not in the parts per billion (ppb)range observed in these shark species. For example, values of barium ranged from 1.6 to 21.5 ppm forblack oreos, from 7.5 to 13 ppm forsmooth oreos and from 1.35 to 3.02 ppm forspiky oreos (Fenton, 1996). The situation was similar in orange roughy with values reported by Edmonds et al. (1991) of 10.03-11.17 ppm. The barium values in the four species of sharks analysed here are thereforeextremely low. d) Lead levels The levels of stable lead in school shark G.galeus varied from 0.60 to 4.79 ppb with no apparent pattern of accumulation with increasing fish length (Fig.28). The stable lead can be described with a mean value of 2.82 ± 1.63 ppb. Nor was any relationship evident for the white spotted dogfish S.acanthias, (Fig. 29), but the range of values varied enormously with a range from 4.02 to 65.66 ppb. The latter value was the highest lead value recorded among the shark species analysed here. Nor was any relationship between stable lead and fishlength evident for C.crepidater (Fig.30). The stable lead values were very low and ranged from Oto 2.26 ppb. A quite differentpattern was found in C. uyato with an exponential decrease in lead value (r2 = 0.658) with increasing fish length (Fig. 31). The values ranged from Oto 10. 77 ppb with the smallest individuals having the highest values of stable lead. This pattern is considered later in relation to ageing this species. In summary the pattern of incorporation of stable lead varied in the different species. No relationship was evident for G.galeus, S.acanthias and C.crepidater

20 D

D 4- D

D 3 - .c c. c. a..c 2- D D I - D

0 I I I I 80 100 120 140 160 180

Fish length cm

Fig.28 G.galeus relationship of lead levels in the vertebrae and fish length.

80 ------

D D 60 -

.c C.40- c. a..c D D 20 - D D 0 -+-----, ----.-,----.-,-----1 60 70 80 90 100 Fish length cm

Fig.29 S.acanthias relationship of lead levels in the vertebrae and fishlength. 5-.------,

4-

3- .c c. c. D a. 2-

1 - D D

0 _,___ _,, ,----,-,---...,...... , --1 1-"7-_--, 50 60 70 80 90 100

Fish length cm

Fig.30 C.crepidater relationship oflead levels in the vertebrae and fish length.

12.5 ------,

D 10

7.5 .c c. c. .c a. 5

2.5

50 60 70 80 90

Fish length cm -o.o 2242.757 * 10 43x r2 = 0.658 y = Fig. 31 C. uyato relationship oflead levels in the vertebrae and fishlength. FINAL REPORT Radiometric Ageing ofSharks however for C.uyato the levels decreased with increasing fish length. Comparing these values to the levels seen in fish otoliths reveals levels ranging from 1.2 to 3. 7 ppb forblack oreos, levels from 1.2-16 ppb for smooth oreos and levels from 1.3 to 5.8 ppb forspiky oreos (Fenton, 1996). Therefore whereas barium levels were an order of magnitude lower in sharks than fish otoliths the stable lead levels in shark vertebrae are equivalent and at times higher than those seen in fishotoliths.

6.4 Radioactive Isotopes

210 a) Pb levels The values for all sharks are given in Table 3. The levels of 210Pb in all the shark species analysed here were very high. The levels forschool shark G.galeus ranging from 0.0824 to 0.2328 dpm.g·1, for white-spotted dogfish S.acanthias ranging from 0.2655 to 0.8597 dpm.g·1, for golden dogfish C.crepidater from 0.2214 to 0.3849 dpm.g·1 and forthe southern dogfish C.uyato from 0.2153 to 0.4133 dpm.g· 1. These levels in vertebrae are almost an order of magnitude higher than any levels seen in fish otoliths. For example in orange roughy the 210Pb values ranged from 0.0033 to a maximum of 0.0504 dpm.g·1. The significance of the high 210Pb values foundis highlighted in Table 4, where a comparison of 210Pb values in the sharks analysed here and a range of other fish and shark species is presented. Levels of 210Pb have also been measured in S.acanthias and G.galeus shark livers with levels of 0.00007 and 0.000012 dpm.g·1 respectively but these are at least one order of magnitude lower than the levels seen in shark vertebrae (Smith and Towler, 1993; Bellamy and Hunter, 1997). For school shark G.galeus a positive linear relationship (r2 = 0.426) was evident between 210Pb and fish length, with levels of 210Pb increasing with fish length (Fig.32). A similar positive linear relationship (r2 = 0.675) was foundfor S.acanthias (Fig.33), although the levels of 210Pb were substantially higher in this species compared to the other sharks analysed.

21 Table 3. Radiometric analysis forthe four species of sharks

Species Fish 210Pb at 210Pb at 226Ra 226Ra 133Ba 210Pb/ 210Pb/ Length collection collection error yield 226Ra 226Ra TL (cm) error Activity Activity ratio ratio error

G.ga/eus 143.2 0.2276 0.0089 0.1700 0.0100 64.23 1.3388 0.0946 G.ga/eus 161.9 0.2328 0.0198 0.0600 0.0200 54.36 3.8799 1.3345 G.ga/eus 112.6 0.1339 0.0098 0.0600 0.0100 59.16 2.2325 0.4064 G.ga/eus 150 0.1545 0.0127 0.0910 0.0018 92.37 1.6978 0.1431 G.galeus 150 0.1639 0.0096 0.0900 0.0200 61.62 1.8210 0.4186 G.ga/eus 88.8 0.1683 0.0133 0.1530 0.0150 93.41 1.0997 0.1384 G.galeus 95.6 0.0824 0.0098 0.0806 0.0089 88.39 1.0221 0.1661

S.acanthias 61.2 0.5104 0.0267 0.2500 0.0300 60.54 2.0415 0.2672 S.acanthias 69 0.4833 0.0200 0.0930 0.0100 83 5.1972 0.5989 S.acanthias 91 0.8597 0.0388 0.0900 0.0100 58.93 9.5526 1.1456 S.acanthias 63 0.2655 0.0143 0.1040 0.0110 84.96 2.5530 0.3031 S.acanthias 73.5 0.4057 0.0169 0.1120 0.0110 89.56 3.6219 0.3864 S.acanthias 65 0.4778 0.0187 0.1170 0.0120 81.6 4.0834 0.4482

C.crepidater 86.4 0.3616 0.0174 0.2600 0.0300 76 1.3908 0.1739 C.crepidater 81.4 0.2214 0.0124 0.1180 0.0120 82.55 1.8764 0.2177 C.crepidater 93.6 0.3540 0.0092 0.1000 0.0100 73.99 3.5405 0.3657 C.crepidater 81.4 0.3849 0.0093 0.0800 0.0100 82.23 4.8107 0.6125 C.crepidater 90.6 0.3709 0.0501 0.0400 0.0100 75.88 9.2714 2.6345

C.uyato 65.6 0.4133 0.0199 0.1960 0.0190 81.17 2.1085 0.2282 C.uyato 58.6 0.2847 0.0164 0.0868 0.0095 87 3.2803 0.4059 C.uyato 80.9 0.3969 0.0246 0.1470 0.0150 82.98 2.7000 0.3224 C.uyato 61.9 0.4108 0.0141 0.0940 0.0093 97.24 4.3698 0.4575 C.uyato 77.1 0.3062 0.0141 0.2250 0.0220 79.79 1.3607 0.1470 C.uyato 65.9 0.2973 0.0121 0.1140 0.0110 96.23 2.6076 0.2732 C.uyato 69.9 0.2881 0.0149 0.1450 0.0150 43.15 1.9872 0.2298 C.uyato 59.2 0.2153 0.0117 0.0668 0.0070 96.01 3.2229 0.3802 Table 4. Examples of values of 210Pb from the literature for shark vertebrae and fish otoliths

Species Total ,!IUPb Author 1 length dpm.g· cm SHARKS Triakis semifasciata 53.0 0.0230 Welden (1984) Leopard Shark 90.7 0.1050 II 140.5 0.1520

Squatina californica 68.2 0.0430 II Pacific angel Shark 107.6 0.2100 II 111.0 0.2250 II

Alopias vulpinus 166.5 0.0470 II Thresher Shark 344.1 0.0790 500.0 0.1720 II

Carcharodon carcharias White Shark inner band 234.0 0.0920 Peripheral band 234.0 0.0990 inner band 393.0 0.1070 Peripheral band 393.0 0.3910 inner band 460.9 0.1970 Peripheral band 460.9 0.3560 inner band 507.9 0.1350 Peripheral band 507.9 0.3060 OTOLITHS Hop/ostethus atlanticus 10.9 0.0033 Fenton et al 1991 Orange roughy 39.2 0.0542 II

Macruronus 95.6 0.0051 Fenton and Short 1994 novaezelandiae Blue Grenadier (Cores) 104.0 0.0078

Al/ocyttus niger 20.7 0.0230 Fenton 1996 Black Oreo 40.4 0.1088 II

Pseudocyttus maculatus 16.1 0.0136 II Smooth Oreo 54.1 0.5675 II

Neocyttus rhomboida/is 15.9 -0.0651 II Spiky Oreo 37.2 0.1769 II 0.3 ------,

0.25

0.2

.Q c.. N 0.15

0.1

0.05 ------80 100 120 140 160 180

Fish length cm y = O.OOlx + 0.012 r 2 = 0.426

Fig.32 G.galeus relationship between 210Pb and fish length.

0.8

.Q c.. 0.6

0.4

D 0.2 60 70 80 90 100

Fish length cm y = 0.015x - 0.537 r 2 = 0.675

Fig.33 S.acanthias relationship between 210Pb and fish length. FINAL REPORT Radiometric Ageing ofSharks

C.crepidater showed a slightly positive linear relationship (r2 = 0.172) even though the size range of individuals analysed was very small (Fig.34). A weak positive linear (r2 = 0.110) relationship between 210Pb and fish length (Fig.35) was also observed forsouthern dogfish C. uyato. There is more variability in the values for fish of similar length in this species. In all four species analysed here there was an increase in the 210Pb with increasing fish length. 210Pb in calcified structures can come from a variety of sources including diet, surrounding water and decay of its grandparent 226Ra. Early work by Holtzman (1967) measured levels of 210Pb and 226Ra in range of aquatic animals including whales and seals. He concluded that the levels of 210Pb reflected diet since the levels where significantly higher than could be accounted for by the decay of 226Ra. The levels of 210Pb in sperm whale teeth were relatively high, high dietary levels in squid explained this. However, later work on age determination of a range of fish species has shown that 210Pb is produced largely by the decay of 226Ra (Fenton et al., 1990; Burton et al. 1999). Welden (1984) reported that the assumption of constant uptake of 210Pb was violated in the 4 species of shark he analysed. In three of the species the angel, leopard and thresher shark whole centrum 210Pb increased with increasing size and age and in the white shark the outer band activities of the three large individual were much higher than those of the small individual. He interpreted this to mean that the rate of incorporation of 210Pb increased in larger older animals or alternatively that there may be a faster rate of turnover of loss of 210Pb in younger individuals. The reason for a non-constant uptake of 210Pb was thought to be due to shifts in diet with growth, or shifts in habitat or metabolic changes with increasing age. Other factors discussed included the violation of a closed system foruptake of material in and out of the calcified vertebrae, however data from Clement (1992) would suggest that a closed system is indeed the case for shark vertebrae. An additional reason was put forward by Welden (1984), that of the decay of 226Ra. This is discussed in the next section of the report.

22 .c a. """"0 N

50 60 70 80 90 100 Fish length cm y = 0.005x - 0.099 r 2 = 0.172

Fig.34 C.crepidater relationship between 210Pb and fishlength.

0.45 T T D D 0.4 .J.. l

0.35

0 """" 0.3 D

0.25

D .L 0.2 55 60 65 70 75 80 85

Fish length cm y = 0.003x + 0.128 r 2 = 0.110

Fig.35 C. uyato relationship between 210Pb and fish length. FINAL REPORT Radiometric Ageing ofSharks

The relationship between the radioactive lead levels and stable lead levels in the shark vertebrae was investigated. In school shark G.galeus (Fig. 36), white spotted dogfish S.acanthias (Fig.37) C.crepidater (Fig.38) and the southern dogfish

C.uyato (Fig.39) there was no relationship between 210Pb and stable lead. That is the levels of radioactive lead present in the shark vertebrae is not linked to the uptake of stable lead from the environment, if bioaccumulation was the cause it would be expected to see this happening for both radioactive and stable lead. Given that in chemical terms 210Pb and Pb would be expected to behave the same way it implies that the primary source of 210Pb is not from the external environment.

Another source of 210Pb is the decay of 226Ra.

226 b) Ra levels The values of 226Ra foundin school shark vertebrae varied from 0.0600-0.1700 dpm.g-1 with a mean value of 0.1007 ± 0.0437 dpm.g-1. Plotting the relationship between 226Ra and fish length shows no relationship (Table 3; Fig.40). In the case of S.acanthias a weak negative linear relationship (r2 = 0.249) was evident (Fig.41) with 226Ra values ranging from 0.0930 to 0.2500 dpm.g-1, with a mean value of 0.1277± 0.0608. 226Ra was higher in one smaller shark, while two other individuals of comparable fish length had lower 226Ra very similar to all other S.acanthias analysed The situation for C.crepidater was more similar to school shark with no obvious relationship between 226Ra and fish length (Fig.42). The values of 226Ra were variable and ranged from 0.0400 to 0.2600 dpm.g-1 with a mean of 0.1196 ± 0.0868 dpm.g-1. However, the situation was quite different for C.uyato with a positive exponential relationship (r2 = 0.546) between 226Ra and fishlength (Fig. 43). Although this represented a relatively small range in values from 0.0668 to 0.1960 dpm.g-1 , with a mean of 0.1343 ± 0.055 dpm.g-1 . Radium was incorporated into the shark vertebrae, the levels recorded were quite similar to those recorded in teleost fish otoliths. A comparison of 226Ra values

23 0.3 ------

0.25 - T D �D "'""I 1 tp 0.2 - E c. T "C D T J.. �D .c 0.15 - D a. ..,.. .L D 0"'"" � N 0.1 - ..,.. D

0.05 I I I I 0 I 2 3 4 5

Pb ppb

Fig. 36 G.galeus relationship between 210Pb and stable lead.

T D .L 0.8 - "'""

C) E c. 0.6 - "C .c D a. � D D 0 "'"" 0.4 - D N

D

0.2 I I I 0 20 40 60 80

Pb ppb

Fig.37 S.acanthias relationship between 210Pb and stable lead. 0.5 ------,

0.4 - I l D �D D -I 0.3 - C, E Q, "C 0.2 -I l a..c 0 - 0.1 -

0 -t----,,�--,,------,,,------,,�---1 0 0.5 1 1.5 2 2.5

Pb ppb

Fig.38 C.crepidater relationship between 210Pb and stable lead.

0.45

T T D 0.4 - T o ol .L

-I 0.35 - C, E Q, - "C .c 0.3 J- D a. ]�.L 0 .L - 0.25 -

T D 0.2 ..L I I I I I I 0 2 4 6 8 10 12

Pb ppb

Fig.39 C. uyato relationship between 210Pb and stable lead. 0.2

T T D 0.15 - D

CU 0:: 0.1 - T co T Cl N D N T 1 T D D 0.05 - .L 1

0 -+----.-,--...... ----. , ---,,------1 80 100 120 140 160 180

Fish length cm

Fig.40 G.galeus relationship between 226Ra dpm.g·1 and fish length.

0.3

0.25

0.2 CU 0:: co N 0.15 N -rD 0.1 o.L "T" ..... D

0.05 60 70 80 90 100

Fish length cm y = -0.003x + 0.322 r 2 = 0.249

Fig.41 S.acanthias relationship between 226Ra dpm.g·1 and fish length. 0.3

0.25 - D

0.2 -

C'CI 0:: 0.15 -

0 I I I 50 60 70 80 90 100 Fish length cm

Fig.42 C.crepidater relationship between 226Ra dpm.g·1 and fish length.

0.25

0.2 D

0.15

C'CI 0::

0.05

0 25 50 75 100

Fish length cm y = 0.010 * I0 °·016x r2= 0.546

Fig.43 C. uyato relationship between 226Ra dpm.g·1 and fishlength. FINAL REPORT Radiometric Ageing ofSharks observed in a range of structures used forageing are given in Table 5.The 226Ra levels in the 4 sharks are really similar to each other and there are similarities to black oreo, but values are higher than those seen forH.atlanticus. 226Ra is actually quite high in these sharks since they are very similar to the levels seen in teleost fish otoliths, which are virtually pure calcium carbonate. For example in sharks the highest measurement of calcium was 2789 ppm, whereas in oreo dories values ranged from 351240-402999 ppm (Fenton, 1996). It is useful to examine the uptake of 226Ra relative to both calcium and barium (a stable equivalent of radium) in the shark vertebrae. Graphs of the relationship between 226Ra versus calcium show a weak negative linear relationship for G.galeus (Fig.44; r2 = 0.291), S.acanthias (Fig.45; r2 = 0.218) and C.crepidater (Fig.46; r2 = 0.251) with a positive linear relationship seen in C.uyato (Fig.47; r2 = 0.391). Examining the relationships between 226Ra and barium show a weak negative linear relationship for G.galeus (Fig.48; r2 = 0.141), a weak positive relationship for S.acanthias (Fig.49; r2 = 0.134) no relationship for C.crepidater (Fig.50) and a strongly positive relationship for C.uyato (Fig.51; r2 = 0.812). Only C.uyato shows a clear relationship between 226Ra, calcium and barium.

) 210 226 c Pb/ Ra Activity ratios The activity ratio 210Pb/226Ra for G.galeus ranged from1.0221 to 3.8799. The relationship between 210Pb/226Ra and fish length showed a weak exponential relationship (Fig.52; r2 = 0.466). The situation forS.acanthias was similar with a 2 strong exponential relationship between 210Pb/226Ra and fish length (Fig. 53; r = 0.789). The activity ratio 210Pb/226Ra ranged from 2.0415 to 9.5526. C.crepidater showed a weak positive linear relationship between 210Pb/226Ra and fishlength (Fig.54; r2 = 0.133), but the range of fishlengths was limited forthis species. The activity ratio 210Pb/226Ra measured in C.crepidater ranging from 1.3908 to 9.2714. The southern dogfish C.uyato showed a negative linear relationship between 210Pb/226Ra and fish length (Fig.55; r2 = 0.368), i.e. the activity ratio decreases with increasing fishlength. This is the reverse of what would be expected

24 Table 5. Comparison of 226Ra values measured in fish otoliths from a range of species. Vertebrae were analysed for shark species indicated by#. (* reflects a mean value)

0 0 "'"' Ra lowest "'"' Ra highest f Species Location Depth (m) dpm.9·1 dpm.1: 1 Author Sebastes West Coast USA Outer 0.033±0.007 0.054±0.0090 Bennett et al. diploproa and Canada continental (1982) shelf and slope Sebastes Nova Scotia 200-900 0.033±0.0020 Campana et al. mentella (1990)* Hoplostethus Southern 750-1000 0.0522±0.0036 0.0625±0.0030 Fenton et al. atlanticus Tasmania (1991)* Anoplopoma California 135-1426 0.288±0.012 0.517±0.021 Kastelle et al. fimbria (1994) Lutjanus Nth Aust Gulf of <55 0.1331±0.0087 0.2277±0.0132 Milton et al. erythroterus Cmpentaria (1994) L.malabricus Nth Aust Gulf of <55 0. 0582±0. 0049 0.2942±0.0141 Milton et al. Carnentaria (1994) L.sebae Nth Aust Gulf of <55 0.046±0.0042 0.2143±0.0114 Milton et al. Carpentaria (1994) Macruronus Southern 500-850 0.0179±0.0026 0.029±0.0036 Fenton and Short novaezelandiae Tasmania (1995) Allocyttus Southern 0.0391±0.0031 0.0694±0.0042 Stewart et al. verrucosus Tasmania (1995) Neocyttus Southern 1000 0.259±0.0070 0.8966±0.0394 Fenton (1996) rhomboidalis Tasmania Pseudocyttus Southern 1000 0.733±0.0343 1. 3409±0. 0609 Fenton (1996) maculatus Tasmania Allocyttus Southern 1000 0.0811±0.0072 0.1782±0.0256 Fenton (1996) niger Tasmania Galeorhinus Bass Strait 0-550 0.0600±0.0100 0.1700±0.0100 This study galeus # Squalus D'Entrecasteaux 40 0.0900±0.0100 0.2500±0.0300 This study acanthias # Channel Tas Centroscymnus Southern 750-1000 0.0400±0.0100 0.2600±0.0300 This study crepidater # Tasmania Centrophorus Bass Strait 400-650 0.0668±0.0070 0.1960±0.0190 This study uyato # 0.2 ------

T D T .L 0.15

C'l:I 0:: 0.1 CD N N OD 0.05 .Ll

0 --1------1 500 1000 1500 2000 2500 3000

Ca ppm y = -0.000x + 0.168 r 2 = 0.291

Fig. 44 G.galeus relationship between calcium and 226Ra.

0.3

0.25

0.2

0:: CD N 0.15 N

0.1

0.05 --1------1 1500 2000 2500 3000

Ca ppm y = -0.000x + 0.353 r 2 = 0.218

Fig. 45 S.acanthias relationship between calcium and 226Ra. 0.3

0.25 D

0.2

CU 0:: 0.15 (0 N N 0.1

0.05

0 1500 2000 2500 3000

Ca ppm y = -0.000x + 0.433 r 2 = 0.251

Fig. 46 C.crepidater relationship between calcium and 226Ra. 0.25 ------.T D

0.2 lTD

CU 0:: 0.15 (0 N N

0.1

D 0.05 -+-----.------,------,,---, 0 500 1000 1500 2000 2500 3000

Ca ppm y = 0.000x + 0.072 r 2 = 0.391

Fig. 4 7 C. uyato relationship between calcium and 226Ra. 0.2

T T D 0.15 D .L "l'"" l I

C,

c. 0.1 "C CU � (.0 N [I] N 0.05 .Ll

0 -1---...---�------,,-----, 10 20 30 40 50 60

Ba ppb 2 y = -0.00lx + 0.148 r = 0.141

Fig.48 G.galeus relationship between 226Ra and Ba.

0.3

0.25 D

"l'""

C, 0.2 c. "C CU 0.15 � (.0 N N 0.1 .....

0.05 25 50 75 100 125 150

Ba ppb

y = O.OOlx + 0.086 r 2 = 0.134

Fig.49 S.acanthias relationship between 226Ra and Ba 0.3

D 0.25 -

0.2 - -I C)

E 0.15 - "t, CU D 0::: 0.1 - D co ..... N D N ..... 0.05 - D

0 I I I I 0 25 50 75 100 125

Ba ppb

Fig. 50 C.crepidater relationship between 226Ra and Ba

0.25 -.------=----,

0.2 -I C) E C. 0.15 "t, CU 0::: co N N 0.1

g 0.05 -+---....---..------,,-----1 0 25 50 75 100 125

Ba ppb y = 0.00lx + 0.068 r 2 = 0.812

Fig.51 C.uyato relationship between 226Ra and Ba 80 100 120 140 160 180 Fish length cm

0.413 0 00 2 0.466 y = * 10 , 5x r =

Fig.52 G.galeus relationship between 210Pb/226Ra and fish length.

14

12

10

N N 6

N 4

2

0 0 25 50 75 100 Fish length cm

9 2 y=0.177*1QO,ol x r =0.789

Fig.53 S.acanthias relationship between 210Pb/226Ra and fishlength. 14

12

10 ID CU a::: CD 8 N N 1 .c 6. a. -N 4 D

2 D

0 50 60 70 80 90 100 Fish length cm y = 0.211x- 14.126 r 2 = 0.133

Fig.54 C.crepidater relationship between 210Pb/226Ra and fish length.

5

TD 4 l

CU a::: CD N 3 T .c D a. 0 1 T -N 2 D

-,- g I 55 60 65 70 75 80 85 Fish length cm y = -0.069x + 7.383 r 2 = 0.368

Fig.55 C.uyato relationship between 210Pb/226Ra and fish length. FINAL REPORT Radiometric Ageing o(Sharks if the activity ratio was to show age. The activity ratio 210Pb/226Ra for C.uyato ranged from 1.3607 to 4.3698.

In summary the activity ratio 210Pb/226Ra in every case was in excess of 1, which means that the amount of 210Pb present was not supported (could not have been totally derived from) the amount of 226Ra present in the shark vertebrae. This was somewhat surprising given the 226Ra values were comparable to that foundin fish otoliths, as previously discussed. However the sharks all had very high levels of

210Pb present. The source of this radioactive lead has already been discussed and given that stable lead values offer no indication of increased uptake of lead in general, the levels of 210Pb are somewhat of a paradox. Using the isotope pair

210Pb/226Ra age determination was not possible, but the option of using 210Pb alone was explored.

6.5 Estimation of shark age Although not ideal it is still possible to estimate ages by using the simple decay of a single isotope, in this case 210Pb. Without a good knowledge of the stable lead and 226Ra uptake patterns forthese species this could not be done with any degree of confidence. The mathematics of this approach is dealt with in detail in Fenton and Short (1992). This is the first time that this particular approach has been used for any fish species. However it has been successfully applied to age clams (Turekian et al. 1975).

Age was estimated using the equation described in Fenton and Short (1992):

AT = l-e·1.T 0 A 11,T

Where AT is the activity at time T A0 is the activity at time 0 A is the decay constant (=ln2/t½) and t½ is the half-life of 210Pb

25 FINALREPORT Radiometric Ageing ofSharks

This equation assumes a constant mass growth. The decay constant for21 0Pb is 0.03114 yr-1. The values of$ used in the equation are critical in determining the age estimate. By using the linear relationships between 210Pb and fishlength for each species the value of$ has been estimated. A value of 0.042 was estimated for G.galeus, this was based on an equation with a r2 value of 0.426. The strongest linear relationship was found in S.acanthias with a r2 of 0.675, the$ value was estimated as 0. 076. However the weaker linear relationships r2 of 0.172 and 0.110 respectively, for C.crepidater and C.uyato results in less confidence forthe selection of the $ value. For these two species a value of 0.1 was chosen. A greater size range of individuals analysed would be required to check the accuracy of the $ value for these two species. Note that by lowering the value of$ the age estimate is increased. The initial 210Pb is higher for the sharks than any fish otoliths analysed in previous studies. This is demonstrated in Table 4.

7. Age Estimation Results and Discussion

For G.galeus the age estimates using this method range from 22 to 55 years (Table 6). Fitting a linear relationship to the radiometric age estimates and adding an estimate of 1 year fora new born shark 30cm in length gives a relationship of y=0.350x-4.408 r2=0.770. While this is somewhat artificial in producing a relationship it does provide a somewhat better basis for estimating age at maturity. Females are recorded to mature around 130cm length, using this equation this gives an age estimate of around 41 years. However looking at the radiometric data does show a range of ages for fishof similar length around 130cm. The radiometric age estimates forschool shark are remarkably simila1· to the known tag return ages forthis species, but are very differentfrom the ages estimated by the alizarin red method used on vertebrae from each of the individuals radiometrically analysed here. The alizarin red method gave ages up to a maximum of 11 years (Fig. 56).

26 Table 6. Radiometric age estimates for the four species of sharks.

Species Fish Age (yr) Positive Negative Length error (yr) error (yr) TL (cm)

G.galeus 143.2 54.27 2.42 2.62 G.ga/eus 161.9 54.99 5.04 5.99 G.ga/eus 112.6 37.23 4.39 5.08 G.ga/eus 150 41.83 4.89 5.77 G.ga/eus 150 43.72 3.56 4.00 G.galeus 88.8 44.58 4.71 5.52 G.ga/eus 95.6 21.64 6.85 8.72

S.acanthias 61.2 61.16 3.20 3.55 S.acanthias 69 58.61 2.62 2.85 S.acanthias 91 77.90 2.78 3.04 S.acanthias 63 40.17 3.29 3.66 S.acanthias 73.5 53.79 2.57 2.79 S.acanthias 65 59.04 2.42 2.62

C.crepidater 86.4 41.28 2.95 3.25 C.crepidater 81.4 25.52 3.41 3.82 C. crepidater 93.6 40.59 1.63 1.71 C. crepidater 81.4 43.28 1.52 1.59 C.crepidater 90.6 42.09 7.68 10.11

C.uyato 65.6 45.57 2.95 3.25 C.uyato 58.6 33.60 3.50 3.93 C.uyato 80.9 44.27 3.75 4.25 C.uyato 61.9 45.37 2.13 2.28 C.uyato 77.1 35.94 2.83 3.10 C.uyato 65.9 34.99 2.51 2.73 C.uyato 69.9 33.98 3.16 3.51 C.uyato 59.2 24.63 3.31 3.69 80 ------,

-l!? ' - T C'IS ° 0 0 Cl) ..... l - l T 0 Cl) l T I 0 Radiometric age en 40 0 � <( .L Alizarin Red Age estimate "C I • s T C'IS 0 E 20 +i 1 w ••• • • 0 • 0 50 100 150 200 Fish length (cm)

Fig. 56 G.galeus age estimates versus fish length.

100 ------,

80 0 7 -l!? C'IS 60 goo 0 -Cl) i en <( "C 40 7 g s E +i 20 - w

0------1 0 20 40 60 80 100 Fish Length (cm)

Fig. 57 S.acanthias age estimates versus fish length. FINALREPORT Radiometric Ageing ofSharks

However Moulton et al. (1992) reported the alizarin technique was unreliable for ageing fish longer than around 130 cm in length. This was made very clear by the fact that using the alizarin method a school shark recaptured 35. 7 years after being tagged and released was aged at being 18-20 years old, when it was evident it exceeded 45 years of age. The results of the present radiometric study confirmthe problem with the alizarin method. More recent work by Francis and Mulligan (1998) in New Zealand aged school sharks by taking x-rays of thin vertebral sections, however they found many sections were unclear and difficult to count. They were reasonably confident with the results for sharks up to 120cm with ages up to 9 years. Growth rate estimates from tag-recapture data suggested fastergrowth for smaller sharks and slower growth forlarger sharks. Their combined results suggested males matured at aboµt 12-17 years and females about 13-15 years. The oldest shark they found they estimated to be 25 years old, but the question of longevity remained unanswered. The question of age at maturity needs better resolution using radiometric analysis, but the data do suggest age at maturity is older than previous techniques have found.

The age estimates for S.acanthias by the radiometric method range from 40 to 78 years (Table 6; Fig.57). By incorporating new born sharks 22cm length into the ages estimates which are known to be 2 years old at birth, gives a linear relationship y=l.084x-18.506 r2=0.886. Given that maturity is about 59cm formales and 80cm forfemales this would correspond to an age of around 45 years for males and 68 years forfemales. But more importantly of the individuals radiometrically analysed, only one was mature. The ages of sharks 61-74cm were estimated to be 40 to 61 years old.

The radiometric ages for S.acanthias do not match the age estimates from counting bands in sections of the second dorsal spine, where the maximum age recorded was 23 years. However although spines were collected from all the individuals analysed radiometrically only one of their spines was readable. This

27 FINAL REPORT Radiometric Ageing ofSharks spine was from a fish 69cm in length and the age was estimated to be 10-11 years old, only two larger sharks were aged using this method. This may relate to the fact that these sharks were all quite old in excess of 50 years (based on radiometric estimates). Scott (1992) conducted a more detailed analysis of the second dorsal spine from S.acanthias in southern Tasmanian waters and reported ages up to 42 years. Interestingly he reported linear growth in this species. This has important implications for the radiometric ageing conducted here which is based on the premise that growth is linear. The second dorsal spine of S.acanthias has been the subject of several ageing studies in several parts of the world. A variety of methods have been applied to this species including x-ray spectrometry by Jones and Geen (1977). They reported an age estimate of a male 83cm in length of 20.6 years. However, after the work of McFarlane and Beamish (1987) it has become widely accepted that this species lives to at least 70 years. The method used by McFarlane and Beamish (1987) was used here. There are several estimates of age at maturity reported in the literature for this species. Saunders and McFarlane (1993) estimated the age of maturity of S.acanthias in British Columbia estimated the median age of maturity for50% of femalesto be 35.5 years. Interestingly their data reported the youngest mature shark to be 24 years old and the oldest to be 62 years of age. These older estimates of maturity are similar to the findingsof the radiometric analysis. Ketchen (1975) reported an age of maturity for S.acanthias of 34 years and described the findings as "startling if not preposterous". However Saunders and McFarlane (1993) discussed these findingstogether with their own similar results by calculating the reproductive potential for female dogfish.They concluded that the trade offbetween growth and reproductive potential was entirely consistent with the apparent delay in maturation. S.acanthias is well known to produce large litters of pups, up to 20 at a time, with gestation lasting about 2 years. The ages estimated for C.crepidater ranged from 25 to 43 years (Table 6), this small range in ages reflecting the small size range of sharks available foranalysis

28 FINALREPORT Radiometric Ageing ofSharks

(Fig.58). The fact that this species is born at 30-35cm in length can be used in drawing a relationship between estimated age and fish length. For this purpose an estimate of 1 year gestation was used. Although by doing this a very good relationship is guaranteed y=0.660x-18.659 r2= 0.875, it is still useful to gain some idea of what age maturity may occur. Given females are reported to mature at 80cm this relationship gives an age of around 34 for maturity. The data itself included two individuals around 80cm in length with ages ranging from 25.5 to 43 years. This is the first estimate of age for this species and therefore no comparison with literature values is possible. The radiometric age method estimated the age of C. uyato ranging from25 to 46 years (Table 6; Fig.59). Again the smaller size range of individuals was reflected in similar ages. This is also the first estimate of age for this species. Less is known about the biology of this species than any of the others analysed here. It is born at about 35cm length, and a specimen 80cm in length was mature (Last and Stevens, 1994). None of the C.uyato analysed here was mature therefore age at maturity exceeds 46 years. Applying a linear relationship between fish length and estimated age y=0.859x-21.508 r2=0.666, age at 80cm would be about 47 years. The age estimates are presented together in Fig. 60 to show the differencesbetween the species more clearly. In all four species the radiometric results point to sharks being much older at maturity than previously thought. Sharks are well known to exhibit a quite differentlife-history pattern than teleost fish.They tend to be k-selected, slow-growing, late to mature, long-lived and having small brood sizes (Smith et al., 1998). Of particular interest in applying the 210Pb decay method forageing sharks is how the method would work for other existing data sets. For example what would calculating the age of orange roughy using a single isotope. mean. In Table 7 age estimates fororange roughy, blue grenadier, and black oreo have been recalculated to see how the 210Pb method compares to the 210Pb/226Ra method. Ages have also been estimated for the four shark species Welden (1984) analysed. This provides very interesting results showing similar ages for all the fish species as was

29 100 ------,

80 D 7 -I!? CU Q) 60 .�!oo D -Q) i C)

0 I I I I I 0 20 40 60 80 100

Fish Length (cm)

Fig. 58 C.crepidater age estimates versus fish length.

50 , TI -o0 40 -I % -I!? L CU Q) 3 ->- 0 T t Q) D C)

sCU E � 10 - wt/)

0 I I I I I 0 20 40 60 80 100

Fish length (cm)

Fig. 59 C. uyato age estimates versus fish length. 90

T 80 - 0 .L

70 - T O,, 60 - _LOO ..L_L.,- -r T - 0 • f ..L• C'l1 .L 50 - _T 1 t::..A Q) -'f.l ...C'l1 40 - 0 �J T E T..L""!"T • t::.. �A ! 1 ! Q) .L .L 30 - Q) T T �r t::.. 0 T - .L .L • 20 1 10 -

0 I I I I I I I I 0 20 40 60 80 100 120 140 160 180 Fish length cm

• G.galeus 0 S.acanthias

0 C.crepidater

A C.uyato Fig 60. Comparison of estimated ages and fish length for all shark species. Table 7. Recalculating ages of literature values using the 210Pb decay equation.

Age Previously Species Total 210pb Ao Estimate Reported Author Comment length using Age cm 210Pb estimate decay (years) (vearsl SHARKS Leopard Shark 53.0 0.0230 0.02 4.49 Welden (1984) Maximum Radiometric reported 48 years Triakis semifasciata for individual 134.2 cm length (whole vertebrae) 90.7 0.1050 0.04 53.25 Resin Section Age 20 for 129.0cm shark and 15 for 134.2 cm shark 140.5 0.1520 0.04 65.13 Pacific angel Shark 68.2 0.0430 0.04 2.32 X-ray Band ages 110cm shark 33 years, Squatina califonica 101.6 cm shark 31 years. Age estimate (whole vertebrae) from growth data 12 and 6 years respectively. Radiometric ages based on dry wt 1-6 years. 107.6 0.2100 0.04 53.25 111.0 0.2250 0.04 55.47 1.00 Thresher Shark 166.5 0.0470 0.04 5.18 Aliopus vulpinus (whole vertebrae) 344.1 0.0790 0.04 21.86 8.00 500.0 0.1720 0.04 46.84 White Shark Carchardon carcharias inner band Peripheral band 234.0 0.0920 0.07 8.78 inner band 234.0 0.0990 0.07 11.13 2 and 2 Age estimate based on x-ray bands and radiometric age using dry wt of vertebrae respectively

Peripheral band 393.0 0.1070 0.07 13.63 inner band 393.0 0.3910 0.07 55.24 9 and 41 Peripheral band 460.9 0.1970 0.07 33.23 inner band 460.9 0.3560 0.07 52.23 13 and 19 Peripheral band 507.9 0.1350 0.07 21.09 507.9 0.3060 0.07 47.37 14 and 26 OTOLITHS Orange roughy Hop/ostethus at/anticus 10.9 0.0033 0.0025 8.92 0.9 Fenton et al Previous age estimates based on 2 1991 10PbJ226Ra method 39.2 0.0542 0.0025 98.79 118 Blue Grenadier Macruronus novaeze/andiae (Cores) 95.6 0.0040 0.0035 4.29 6.4 Fenton and Short 1994 104.0 0.0078 0.0035 25.73 17.9 Black Oreo Allocyttus niger 20.7 0.0230 0.01 26.75 19.6 Fenton 1996 40.4 0.1088 0.01 75.87 91.8 FINAL REPORT Radiometric Ageing ofSharks determined using 210Pb/226Ra. Welden's work used the 210Po /210Pb isotope pair to estimate ages and also used x-ray band counts. However his data was suitable for analysis using 210Pb alone.

In summary, using 210Pb alone works well and compares very favourably with the ages determined using 210Pb/226Ra. This finding also helps give confidence to the results forthe four species of sharks analysed in the present study.

8. Benefits Age estimates have been provided for the four species of shark examined here. These results have potential for incorporation into management arrangements for these species, particularly forschool shark. This project has shown that the radiometric technique has applicability not only forfish otoliths but also forcalcified shark vertebrae to provide age estimates.

9. Further Development The technique has shown promise. Further development and trials of the method on a wider size range of sharks and also include any known-age sharks when available would be obvious next steps. The analytical technique itself has undergone some developments in the USA over the last few years for radium measurement. Burton et al. (1999) applied a method developed as part of a masters thesis by Andrews (1997). The method uses thermal ionization mass spectrometry to more accurately measure 226Ra, the process involves separation of 226Ra from calcium and barium using cation-exchange columns. While this method appears to offer some advantages, the measurement of 210Pb remains unchanged. The limited expertise in Australia for using this method is worth addressing. At present only ANSTO offersa commercial service foranalysing samples for ageing fish and there is currently no research provider with a commitment to continuing research in this area. Nearly all the research conducted in Australia

30 FINALREPORT Radiometric Ageing ofSharks using this method has been funded by FR&DC and its predecessors. To lose the expertise developed is a concern, given the value of the method to understanding fish age. It is now over 10 years since the first results using radiometric analysis showed the potential of the method. It is perhaps time to adopt the method into the tool-box for fish ageing. It is a cost-effective approach to solving one of the most difficult problems facing fisheriesbiologists.

10. Conclusion

The results of this study are promising. This is the first time that any method has shown ages anywhere near what is known from tag-returns for school shark G.galeus. The age estimates for S.acanthias have also demonstrated longevity similar to that seen elsewhere in the world. It is also the first time that ages have been estimated for deep-water dogfish C.crepidater and C.uyato. The technique offers some real hope for ageing sharks with greater confidence than ever before.

31 FINALREPORT Radiometric Ageing ofSharks

11. References Anon. (1991) School shark recaptured 42 years after tagging. Australian Fisheries (May) 5. Beamish, R.J. and McFarlane, G.A. (1985) Annulus development on the second dorsal spine of the spiny dogfish (Squalus acanthias) and its validity for age determination. Canadian Journal of Fisheries and Aquatic Sciences 42:1799-1805. Bellamy, P. and Hunter, K.A. (1997) Accumulation of 210Po by spiny dogfish

(Squalus acanthias), elephant fish (Callorhinchus milii) and red gurnard

(Chelodonichthys humu) in New Zealand shelf waters. Mar. Freshwater Res. 48:229-234 Burton, E.J., Andrews, A.H., Coale, K.H. and Cailliet, G.M. (1999) Application of radiometric age determination to three long-lived fishes using 210Pb:226Ra disequilibria in calcified structures: A review. American Fisheries Society Symposium 23:77-87 Cailliet, G.M. (1990) Elasmobranch age determination and verification : and updated review. In Pratt, H.L.J., Gruber, S.H. and Taniucgu, T. (eds) Elasmobranchs as Living Resources: Advances in the Biology, Ecology and Systematics and the Status of Fisheries (pp.157-165). NOAA Technical Report NMFS Circular. Campana, S.E., Zwanenbm·g, K.C. and Smith, J.N. (1990) 210Pb/226Ra determination of longevity in redfish. Can. J. Fisheries and Aquatic Sciences, 47: 163-165. Caton, A and McLaughlin, K. (Eds) (2000) Fishery Status Reports 1999. Resource Assessments of Australian Commonwealth Fisheries. Agriculture, Fisheries and Forestry, Australia, and Bureau of Rural Sciences. Australian Government Printers, Canberra. Compagno, L.J.V. 1984 FAO Species Catalogue. Vol.4. Sharks of the World. An Annotated and Illustrated Catalogue of Shark species known to date. Parts 1 and 2. FAO Fish Synop. (125) 4 (1,2) Rome 655pp

32 FINAL REPORT Radiometric Ageing ofSharks

Compagno, L.J.V. 1988 Sharks of the Order Carcharhiniformes. Princeton, New Jersey, Princeton University Press. Cochran, J. K., & Landman, N. H. (1984). Radiometric determination of the growth rate of Nautilus in nature. Nature, 308, 725 - 727. Edmonds, J.S., Caputi, N. and Morita, M (1991) Stock discrimination by trace­ element analysis of otoliths of orange roughy (Hoplostethus atlanticus), a deep water marine teleost. Aust.J. Mar and Freshw. Res. 42:383-389 Fenton, G.E., Short, S.A. and Ritz, D.A. (1991) Age determination of Orange Roughy, Hoplostethus atlanticus (Pisces:Trachichthyidae) using 210Pb/226Ra disequilibria. Marine Biology 109:197-202 Fenton, G.E. and Short, S.A.(1992). Fish age validation by radiometric analysis of otoliths. Australian Journal of Marine and Freshwater Research 43: 913-922 Fenton, G.E. and Short, S.A. (1995). Radiometric Analysis of Blue Grenadier Macruronus novaezelandiae Otolith Cores. Fishery Bulletin 93:391-396. Fenton, G.E. (1996) Age Determination of oreo dory species by radiometric analysis. FR & DC grant 92/41 Final Report. Ferreira, B.P. and Vooren, C.M. (1991) Age, growth and structure of vertebra in the school shark Galeorhinus galeus (Linnaeus, 1758) from southern Brazil. Fishery Bulletin 89:19-31 Francis, M.P. and Mulligan, K.P. (1998) Age and growth of New Zealand school shark Galeorhinus galeus. New Zealand Journal of Marine and Freshwater Research 32:427-440. Joll, C. (1993) Conference bites into southern shark problems. Australian Fisheries 52(6):6-10 Jones, B.C. and Geen, G.H. (1977) Age determination of an Elasmobranch (Squalus acanthias) by x-ray spectrometry. J.Fish.Res.Board Can. 34: 44-48 Kalish, J.M. (1989a) Fish otolith chemistry as an indicator of physiological, ecological and environmental events. Unpubl. Ph.D thesis, Department of Zoology, University of Tasmania.

33 FINAL REPORT Radiometric Ageing ofSharks

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Appendix 1 :Intellectual property arising The applicability of ageing shark vertebrae usmg the decay of 210Pb was explored. All techniques used for radiometric analysis followed previous work developed under earlier grants from FR&DC and the Australian Research Council (ARC). The methods of cleaning the vertebrae have application for further radiometric analytical studies of sharks. The results from this study will be published in scientific journals and are of no direct commercial value.

Appendix 2: Staff Dr. Gwen Fenton, Project leader Mr Mathew Healey, Zoology Dept. Technical assistant Mr Rob Chisari, Australian Nuclear Science and Technology Organisation conducted all the radiometric analyses under commercial contract.

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