I . . . RADIOMETRIC AGE DETERMINATION OF THE GIANT GRENADIER (A/batrossia pectoralis) USING 210Pb: 226Ra DISEQUILIBRIA
A thesis submitted to the faculty of San Francisco State University in partial fulfillment of the requirements for the degree
Master of Science in Marine Science
by
Erica Janis Burton
San Francisco, California
December, 1999 Copyright by Erica Janis Burton 1999 RADIOMETRIC AGE DETERMINATION OF THE GIANT GRENADIER (Aibatrossia pectoralis) USING 210Pb: 226 Ra DISEQUILIBRIA
Erica Janis Burton San Francisco State University 1999
Age estimates determined from growth increments in sagittal otolith sections
indicated that Albatrossia pectoralis is slow growing (K :<:: 0.023) and lives up to
56 years. Growth increments found in otolith sections, however, were difficult to
interpret. The von Bertalanffy growth function for A. pectoralis otolith section age
estimates did not fit size-at-age data well. To validate age and longevity
estimates, ages were determined using the radioactive disequilibria of 210Pb: 226 Ra
in otolith cores from adult A. pectoralis. Radiometric and growth increment ages
agreed for 6 of the 12 pooled otolith age-groups. Radiometric age determination
confirmed longevity to at least 32 years for females and 27 years for males.
Additional age and longevity estimates are still necessary to develop an informed
fishery management plan for A. pectoralis.
I certify that the Abstract is a correct representation of the content of this thesis. ~~~-~ (Date)
- ACKNOWLEDGEMENTS
Although a thesis is authored by one person, it is not accomplished alone.
I have many people to thank who contributed their time, sweat, and talent. I sincerely thank my thesis committee members. Dr. Gregor Cailliet provided advice, guidance, support, and trust throughout my graduate career at MLML.
Dr. Kenneth Coale enthusiastically explained radiochemistry and decay mathematics with unceasing encouragement and confidence. Dr. Ralph Larson eagerly accepted another graduate student studying radiochemistry and
expeditiously edited the manuscript with insightful advice. Specimens, otoliths,
and length measurements were collected by scientists from the Alaska Fisheries
Science Center, including Bob Lauth, Jerry Hoff, Bill Flerx, Robin Harrison,
Michael Martin, Terry Sample, and Skip Zenger. Special thanks to Bob and Jerry
for always offering to sample Albatrossia pectoralis, choreographing the "slime
crew", and graciously accepting any and all collection requests. In addition,
valuable ship-time was provided by the National Marine Fisheries Service.
Chuck Crapo from the Fishery Industrial Technology Center at the University of
Alaska Fairbanks in Kodiak, Alaska learned how to extract otoliths frorn A.
pectoralis, and collected otoliths and length measurements (including the rare
and invaluable total length measurements) during his own study, "Utilization of
v Giant Grenadier." Bob Lea from California Department of Fish and Game,
Monterey, and Mike Hosie from Oregon Department of Fish and Wildlife,
Charleston donated otoliths from larger specimens captured by commercial fishermen. Pete Holden at the University of California, Santa Cruz measured radium in otolith samples using the thermal ionization mass spectrometer. Brown
Lines Trucking Company donated shipping supplies and the expense for delivery of 1 ton of fish collected by the Alaska Fisheries Science Center. Lara Ferry
Graham, Allen Andrews, and Leigh Nerney helped extract otoliths and recorded length from 1 ton of fish. Special thanks to Lisa deMarignac and Allen Andrews for reading 50 extremely difficult-to-age otoliths several times. My literature collection would not be complete without the help of librarians Joan Parker and
Sheila Baldridge, and their assistants Sandy O'Neil, Crystal Chisolm, Sally
Wittlinger, Terry Darcy, Stephanie Nichols, and Kim Puglise. Gail Johnston,
Sandy Yarbrough, and Kathleen Baker made the distance between Moss
Landing and San Francisco State University seem not so far. Andrei Suntsov
from the Russian Academy of Sciences in Moscow expediently and afford ably
translated three Russian papers into English. Kate Stanbury illustrated the map
of sampling locations. Special thanks to my partners in crime, Allen Andrews
and Jocelyn Nowicki Douglas, for their guidance in the radiochemistry lab, and
vi perseverance during mathematical chaos. Finally, I am ever grateful to my parents for their love and continued support throughout my education.
This research was funded in part by the Dr. Earl H. Myers and Ethel M. Myers
Oceanographic and Marine Biology Trust; and by a grant from the National Sea
Grant College Program, National Oceanic Atmospheric Administration, U.S.
Department of Commerce, under grant number NA36RG0537, project number
R/F-148 through the California Sea Grant College System. The views expressed herein are those of the author and do not necessarily reflect the views of NOAA or any of its sub-agencies. The U.S. Government is authorized to reproduce and distribute for governmental purposes.
vii TABLE OF CONTENTS
List of Tables ...... viii
List of Figures ...... ix
Introduction ...... 1
Methods ...... 8 Partial length analysis ...... 9 Otolith size and fish length analysis ...... 10 Age estimation ...... 11 Radiometric analysis ...... 13 Core extraction and age-group determination ...... 13 210Pb determination ...... 16 226Ra determination ...... 21 Radiometric age determination ...... 21 Growth ...... 23
Results ...... 25 Partial length analysis ...... 26 Otolith size and fish length analysis ...... 28 Age estimation ...... 30 Radiometric analysis ...... 33 Core extraction and age-group determination ...... 33 210 Pb and 226Ra determination ...... 35 Radiometric age determination ...... 36 Growth ...... 37
Discussion ...... 39 Partial length analysis ...... 41 Otolith size and fish length analysis ...... 41 ~eestimation ...... ~ Radiometric analysis ...... 45 Growth ...... 47 Fishery ...... 52
Literature Cited ...... 57
viii LIST OF TABLES
Table Page
1. Capture dates, gegraphic location, and depth of Albatrossia pectoralis specimens collected during research cruises ...... 66
2. Capture dates, general region, and depth of Albatrossia pectoralis specimens collected by commericial fishermen ...... 67
3. Precision of Reader 1 age estimates ...... 68
4. Ra-226 determination for whole Albatrossia pectoralis otoliths ...... 69
5. Otolith core age-groups used for radiometric analyses ...... 70
6. Radiometric results for pooled Albatrossia pectoralis age-groups ...... 71
7. Von Bertalanffy growth parameters for Albatrossia pectoralis pre- anal fin length and estimated age data ...... 72
8. Gompertz and linear growth parameters for Albatrossia pectoralis pre-anal fin length and estimated age data ...... 73
9. Von Bertalanffy growth parameters for Albatrossia pectoralis pre- anal fin length and radiometric age data ...... 74
ix LIST OF FIGURES
Figure Page
1. Length measurements determined for Albatrossia pectoralis ...... 75
2. Map of North Pacific Ocean with Albatrossia pectoralis capture locations ...... 76
3. Linear relationship between pre-anal fin length and total length ...... 77
4. Linear relationship between head length and total length ...... 78
5. Length frequency distribution for male and female Albatrossia pectoralis captured in the North Pacific Ocean ...... 79
6. Whole Albatrossia pectoralis otolith ...... 80
7. Linear relationship between pre-anal fin length and otolith length ...... 81
8. Allometric growth relationship between pre-anal fin length and otolith weight ...... 82
9. Transverse otolith section of a 33 year-old Albatrossia pectoralis female ...... 83
10. Precision of Reader 1 age estimates of Albatrossia pectoralis ...... 84
11 . Precision of age estimates between three readers of Albatrossia pectoralis ...... 85
12. Age-bias plots for each of the pairwise reader comparisons ...... 86
13. Expected 210Pb: 226Ra activity ratio ingrowth curves and observed activity ratios at predicted age for male and female Albatrossia pectoralis ...... 87
X 14. Comparison of mean predicted age and radiometric age for male and female Albatrossia pectoralis pooled otolith age-groups ...... 88
15. Estimated age at pre-anal fin length for male and female Albatrossia pectoralis ...... 89
16. Radiometric age at mean pre-anal fin length for male and female Albatrossia pectoralis pooled otolith age-groups ...... 90
17. Comparison of von Bertalanffy growth functions among three ageing studies of Albatrossia pectoralis ...... 91
xi INTRODUCTION
The giant grenadier, Afbatrossia pectoralis, is a deep-water, benthopelagic macrourid found on the continental slope of the North Pacific Ocean in depths of
140 to 2,189 m (Iwamoto and Stein 197 4, Allen and Smith 1988, Cohen et al.
1990). It has a wide distribution: from northern Japan to the Okhotsk and Bering
Seas, east to the Gulf of Alaska, and south to northern Baja California (Cohen et al. 1990). It is the largest macrourid known, reaching approximately 150 em in total length (Iwamoto and Stein 197 4 ). Albatrossia pectoralis has been collected frequently in large numbers during deep-water trawl surveys in the Sea of
Okhotsk, Bering Sea, Gulf of Alaska, and off the Aleutian Islands (Morris et al.
1983; Ronholt et al. 1986; Tuponogov 1986, 1997).
With the collapse and closure of fisheries on the continental shelf, fishers are turning to deep-water stocks on the continental slope, including macrourids
(Merrett and Haedrich 1997). Like their valuable commercial cod relatives, macrourids possess characteristics with economic potential: they are widespread and diverse, many inhabit the upper continental slope, are fairly large, and can be quite abundant. Canadian, European, and Soviet fisheries exist in the North
Atlantic for Macrourus berg/ax (roughhead grenadier) and Coryphaenoides rupestris (round nose grenadier), and have been fished for decades (Maucorps and Fontaine 1979, Geistdeorfer 1982, Atkinson 1995). Along the Pacific coast,
Coryphaenoides acrolepis (Pacific grenadier) is the target of a relatively new
1 directed fishery off California and Oregon (Andrews 1999a). The fishery in
Monterey Bay, California grew substantially frorn practically zero landings during
1992 to the fifth largest fishery during 1996 (900 tons; Leos 1996, 1997; Andrews et al. 1999a). This is a dramatic example of what can happen when the target shifts.
Until recently, macrourid species were not targeted by United States fisheries, but were caught incidentally by trawl and longline fishermen.
Macrouridae was considered one of the most abundant families of fishes captured as bycatch in the Bering Sea and Aleutian Island regions, and were categorized as noncommerical, nonspecified species by the National Marine
Fisheries Service and the North Pacific Fishery Management Council (Bakkala
1984 ). Grenadiers continue to comprise a significant portion of bycatch in
Alaska's flatfish and sablefish fisheries; fishermen report up to 40% of the fish caught during deep-sea trawling can be grenadiers (Crapo et al. 1999).
Grenadier bycatch has created an interest in its use as a food product. A taste test panel, however, found the flesh of A. pectoralis had exceptionally poor
qualities for human consumption, including poor texture, taste, and minimal
protein content (Matsui et al. 1990). The method of processing A. pectoralis for
human consumption continues to improve (Charles Crapo, University of Alaska,
Fishery Industrial Technology Center, 900 Trident Way, Kodiak, Alaska 99615,
2 personal communication). Besides C. acrolepis, most grenadier landed are used currently as fish meal or fertilizer (Matsui et al. 1990, Andrews et al. 1999a).
Determining the age and growth of fish is an important tool for fishery biology and ecology. Age and length data can provide information about stock composition, age at maturity, longevity, and mortality. The most common method of age determination involves counting growth increments deposited in calcified structures such as otoliths (Williams and Bedford 197 4, Chilton and
Beamish 1982). Three pairs of otoliths exist in the inner ear of fishes; the largest of these, the sagitta, is the most commonly used in ageing studies. Otoliths are composed of calcium carbonate crystals (aragonite) intersected by an organic fibrous protein matrix (otolin; Degens et al. 1969), and growth occurs through differential deposition of these two substances around a central nucleus
(Dannevig 1956, lrie 1960, Campana and Neilson 1985). Patterns of alternating aragonite and otolin bands are visible on the otolith surface and in a transverse
(dorsal-ventral) cross section (Panella 1980). The periodicity of these alternating patterns (e.g. daily, seasonal, annual) should be investigated for their true temporal meaning (Williams and Bedford 1974, Beamish and McFarlane 1983).
Relationships between fish length, otolith morphometries or weight, and age often are investigated for several reasons. The first reason, to determine whether the potential ageing structure (e.g. the otolith) increases in size as the fish grows, is essential for ageing studies. The second reason is to describe the
3 relationship between age and fish size. An additional reason, which will be described later, is to have criteria available for pooling otoliths of similar sizes or weights, therefore fish of similar sizes or ages, for radiometric age determination.
Age estimates from growth increments in macrourid sagittal otoliths indicate grenadiers are long lived, slow growing, and mature late in life. Based on counts of otolith increments, Bergstad (1990) and Kelly et al. (1997) estimated the age of Coryphaenoides rupestris to 50 to 72 years and maturity at 8 to 10 years. Coryphaenoides acrolepis may reach 56 years of age (Andrews et al.
1999a), and females mature at approximately 20 to 40 years at 23 to 65 em TL
(Stein and Pearcy 1982, Matsui et al. 1990). Albatrossia pectoralis sexually matures at 50 to 56 em TL, one-third of its maximum total length (Novikov 1970).
Few researchers have estimated the age of A. pectoralis, and results are suspect, because of the structures (scales) used to estimate age. Validated
(accurate) and verified (precise) estimates of age composition, age at maturity, and longevity for A. pectoralis do not exist.
Traditional age validation methods require examination of known-age fish obtained through mark-and-recapture studies or laboratory rearing (Beamish and
McFarlane 1983). Mark-and-recapture techniques are impractical for deep-water fishes such as grenadiers, because barotrauma precludes vital marking, and recapture probability is low. Laboratory rearing is also difficult, because little is
known of A. pectoralis early life history.
4 Fortunately, the naturally occurring radioisotope pair, radium-226 (226Ra) and its daughter product lead-210 e' 0Pb), found in calcified structures of fishes can act as a built-in chronometer (Smith et al. 1991, Fenton and Short 1992).
This radioisotope pair is useful for ageing long-lived fishes as old as 120 years.
Radiometric ageing methods have been used successfully to confirm longevity for several deep-water fishes (Bennett et al. 1982, Campana et al. 1990, Fenton et al. 1991, Watters 1993, Kastelle et al. 1994, Kline 1996, Andrews et al.
1999a).
Radiometric age determination of fishes relies on the incorporation of
226Ra (a water soluble calcium analog) from the environment into the calcified matrix of otoliths and skeletal structures (Smith et al. 1991, Fenton and Short
1992). After incorporation, 226Ra decays through a series of short-lived daughter
isotopes to the more stable isotope 210Pb. Because the parent and daughter
isotopes of radium are not calcium analogs and are relatively insoluble or short
lived in seawater, therefore less abundant, they are not readily incorporated into
calcified tissues. Lead-21 0 is generated in situ within the otolith by radioactive
decay of 226Ra, which is called ingrowth (Fenton and Short 1992). The half-life of
226 210 Ra (t112 = 1 ,600 y) is sufficiently greater than that of Pb (t112 = 22.3 y);
therefore, it does not decay significantly during the period of 210Pb ingrowth and
can be considered constant. Upon radium incorporation into otoliths, radioactive
disequilibrium exists between 226Ra and 210Pb. Through time the nuclide pair will
5 approach the equilibrium state, at which time the two nuclides decay at the same rate (lvanovich 1992, Cowart and Burnett 1994 ). The activity ratio of the two
nuclides will approach one, known as secular equilibrium. Measurement of the
parent and daughter product ratio e'"Pb:226Ra) during the state of disequilibrium
permits an age determination since the time of radium uptake. The result is a
radiochemical age estimate, which is then compared with age estimates from
otolith growth increments.
Fish age can typically be calculated using radiometric analysis if three
assumptions are met. First, there must be negligible, postformational, internal
migration of radionuclides across internal otolith increments (i.e. the otolith acts
as a closed chemical system for 226Ra and its daughter products). Violation of a
closed system is unlikely in otoliths, because it consists of a well regulated
aragonitic lattice where crystalline growth is directionally regulated by polyanions
(Wheeler and Sikes 1984 ); and otolith resorption appears to occur rarely, if ever
(Campana 1983, lchii and Mugiya 1983, Yoklavich and Boehlert 1987). In
addition, a significant loss has not been documented in more porous forms of
calcium carbonate, such as corals (Bender 1973, Moore et al. 1973, Dodge and
Thompson 1974 ).
Second, the initial activity ratio of 210Pb: 226Ra in otoliths should be much
smaller than one, ideally close to zero, and is known or measured (i.e. 210Pb is
insignificant during formation of the calcified structure). This assumption can be
6 investigated by measuring 210 Pb in otoliths of young fish. Coring otoliths
(extracting a rectangular block around the otolith nucleus resembling the size and shape of a juvenile otolith) may avoid problems due to varying uptake ratios at different life stages, because juveniles are thought to accumulate the daughter: parent pair of isotopes in a constant ratio.
Third, the uptake rate of the parent radioisotope {'26 Ra) is proportional to
mass growth of the otolith during the lifetime of the fish. This assumption can be
limited to the period of core formation when restricting the analysis to the oldest
portion of the otolith by removing exterior otolith layers (Campana et al. 1990).
When using otolith cores and measuring specific activities of 226Ra and 210 Pb for
each sample being radiometrically aged, the third assumption becomes
unnecessary.
Recently, Andrews et al. (1999b) developed a new 226Ra separation
technique to improve radiometric age determination of fishes. Compared to
methods used in the past, this new technique measures 226Ra atoms directly
using thermal ionization mass spectrometry (TIMS), requires less calcified
material (0.1 to 1.0 g), less processing time (7 to 10 days), and analytical
uncertainty is usually less than 1.5%. As a consequence, Andrews et al. (1999a)
successfully determined age and confirmed longevity of C. acrolepis.
In this study, age was estimated from growth increments found in
sectioned A. pectoralis sagittal otoliths, and compared with radiometric ages
7 determined using the disequilibria of 210 Pb: 226 Ra in otolith cores. Six questions were addressed in this study: 1) can total fish length be predicted from partial length? 2) is there a relationship between fish length, and otolith morphometries or weight? 3) what is the precision of age estimates among and between readers? 4) do otolith section ages agree with radiometric ages? and 5) what are the growth characteristics and longevity of A. pectoralis?
METHODS
Albatrossia pectoralis was collected using bottom trawls within the
northeast Pacific Ocean during research cruises conducted by the Alaska
Fisheries Science Center, National Marine Fisheries Service (AFSC) and the
Fishery Industrial Technology Center, University of Alaska Fairbanl
Otoliths from several specimens, captured by commercial fishermen, were made
available by the Oregon Department of Fish and Wildlife (ODFW) and the
California Department of Fish and Game (CDFG). Capture location, date, sex,
and fish length to the nearest centimeter (head length; pre-anal fin length; and
total length, if tail intact; Fig. 1) were recorded. Sagittal otoliths were removed,
rinsed with water or ethanol, and stored either dry in coin envelopes or in glass
vials containing ethanol (50-90%). Most specimens were processed fresh;
others were frozen and processed later.
8 Partial length analysis
Macrourids have a characteristic shape with a large head and a long tail that tapers to a point. Tail breakage and regeneration cause problems obtaining reliable total length (TL) measurements. Partial lengths have been recommended as replacements for macrourid total length (Jensen 1976;
Atkinson 1981, 1991; Kelly et al. 1997). In addition, NAFO (North Atlantic
Fisheries Organization) and ICES (International Council for the Exploration of the
Sea) have adopted anal fin length (tip of snout to base of first anal fin ray) as the standard length measurement for C. rupestris and M. berg/ax; NAFO 1980,
Sahrhage 1986). Atkinson (1981) concluded anal fin length was more practical than pre-anus length (tip of snout to anus), because the latter is sometimes affected by distortion of the anus due to air-bladder expansion and extrusion of intestines when fish are brought to the surface from depth.
To determine if total length could be predicted from a partial length, two
partial lengths were measured and compared to total length using linear regression analyses. Head length (HL; tip of snout to posterior edge of
operculum), pre-anal fin length (PAF; tip of snout to base of first anal fin ray), and
total length (TL; if tail intact), were measured to the nearest centimeter (Fig. 1 ).
Only specimens with intact tails were used for partial length analysis. To test for
significant differences (a.= 0.05) between the sexes for each partial length
comparison, a test for coincidental regressions was used (F test; Zar 1984 ). If
9 there was no difference between the sexes, the slope of the combined regression was tested for a significant difference (a= 0.05) from zero using an analysis of variance (ANOVA).
Otolith size and fish length analysis
Sagittal otoliths were air-dried (if previously stored in ethanol) and otolith morphometries were measured to the nearest 0.1 mm with an image analyzer
(Bausch and Lomb Monozoom 7 lens and dissecting microscope attached to a
Macintosh® IICX computer equipped with the image processing and analysis program Image; Rasband 1993). Dial calipers were used if otoliths were too
large for the image analyzer camera lens. Otoliths were weighed to the nearest
milligram. Left and right otoliths were analyzed for size differences using a
paired-sample t-test. Otoliths from male and female specimens were combined
for to test for differences between left and right otoliths.
To determine if there was a relationship between otolith morphometries or
weight with fish length, linear and allometric functions were used to compare
otolith length, height, thickness, and weight to pre-anal fin length. To test for
significant differences (a= 0.05) between the sexes for each otolith size
comparison, a test for coincidental equations was used (Zar 1984 ). If there was
no difference between the sexes, the combined function was tested for
significance (a= 0.05) using analysis of variance (AN OVA).
10 Age estimation
To estimate age, several otolith preparation methods were attempted, including whole, break-and-burn, sectioning, and staining. Thin transverse sections provided the clearest growth increments. Consequently, one otolith from each sagittal pair was transversely sectioned and growth increments counted. Each otolith was centered and affixed to a heavy-duty paper merchandise price tag (American Tag Co.; 1.5 x 1 inch) with double-faced tape and embedded in polyester fiberglass resin (Bondo®) in preparation for sectioning. Otoliths were sectioned transversely around the nucleus on a
Buehler lsomet™ low-speed saw with two Norton® low density diamond blades separated by two 0.3 mm plastic spacers. Sections were removed from tags and polished with a Buehler Ecomet® Ill grinding wheel using 800 and 1200 grit silicon carbide wet-dry grinding paper. Polished sections were then mounted to individually labeled microscope slides with CytosealrM mounting medium.
Mounted sections were polished again using 800 and 1200 grit silicon carbide wet-dry grinding paper. Polishing otolith sections before and after permanently mounting to slides provided better increment resolution and eliminated surface artifacts. Otoliths were viewed in water with transmitted light under an Olympus
dissecting microscope between 31.5 and SOx magnification.
Growth increments were counted independently by three readers at Moss
Landing Marine Laboratories. Reader 1 (the author) examined all otolith sections
11 for readability. Otolith sections were categorized on a five-point quality scale
(bad, poor, fair, good, or excellent). Otolith ratings were based on the quality of the otolith section and the reader's confidence of an age estimate. Reader 1 estimated age five times for each otolith that was rated "poor" or better. A subset of fifty randomly selected otoliths, previously aged by Reader 1, were available to
Readers 2 and 3 for age estimation. Readers 2 and 3 examined each otolith three times.
To determine a final age within readers, an estimate that was similar for at least two readings was chosen. If no readings were similar, the last estimate was chosen. If there were two pairs of similar age estimates, which was possible for Reader 1 (n = 5), the latter pair was chosen.
To compare the reproducibility of age estimates among and between readers, average percent error (APE; Beamish and Fournier 1981 ), coefficient of variation ( V) and index of precision (0; Chang 1982) were calculated. Percent agreement between age estimates for each reader, and between final ages of
Readers 1, 2, and 3 were calculated. In addition, the variability of Reader 1 age estimates was analyzed as a function of specific age-groups and sex. Age bias plots were constructed to identify any systematic differences between readers
(Campana et al. 1995). Reader 1 age estimates were used for all subsequent analyses including radiometric age comparisons and growth curve analyses.
12 Radiometric analysis
Prior to otolith core extraction and radiometric age determination, radium e26Ra and 228Ra) was measured in whole otoliths using isotope-dilution thermal ionization mass spectrometry (TIMS) to investigate 3 uncertainties: approximate
226Ra activity in A. pectoralis otoliths, the presence of natural 228Ra (ultimately added to core samples as a tracer), and approximate sample weights required for radium analysis. Radium separation and determination methods are explained below.
Core extraction and age-group determination
The third radiometric assumption (i.e. growth assumed to be constant during the first few years of life) is unnecessary when otolith cores are used.
Consequently, using otolith cores reduces the error associated with using whole otoliths (Bennett et al. 1982, Campana et al. 1990). In this study, a core size of approximately 5 years was chosen because 1) it was young enough to assume constant radium uptake during the juvenile phase; 2) it was large enough to minimize the number of otoliths pooled into an age-group; and 3) it was the minimum core size that could be repeatedly extracted. In addition, radiometric age determination was successful for C. acrolepis using 5-year cores (Andrews
et al. 1999a).
13 Small or juvenile fish were not captured; therefore, otolith core size had to be estimated from adult fish. Otoliths were sectioned in two dimensions
(transverse and frontal) to estimate core width, height, and thickness. Otoliths were ground to core size by hand with a Buehler Ecomet® Ill grinding wheel using 320 grit silicon carbide wet-dry grinding paper. To achieve adequate counting statistics, a minimum of 0.5 g of core material is recommended
(depending on activities) for 210 Pb and 226Ra analyses (Andrews et al. 1999a, b).
To acquire enough otolith material for a 0.5 g sample, and to maximize the number of age-groups radiometrically analyzed from the otoliths available, age estimates had to be predicted from unsectioned otoliths. To predict ages of unsectioned otoliths, multiple and simple linear regression analyses of fish size and/or otolith size to age estimates from previously aged otolith sections were conducted using the statistical computer program SYSTAT® (SYSTAT, Inc.
1992). Within reader age estimates with V < 10% were used in regression analyses. Males and females were analyzed separately. Multiple regression models were similar to those used by Boehlert (1985): otolith section age was the dependent variable, and independent variables included pre-anal fin length, head length, otolith weight, otolith length, the respective square and cubic terms of each, and interaction variables. Simple linear regression models included log transformed age as the dependent variable, and log-transformed otolith weight as the independent variable.
14 To choose the best independent variable (or subset of independent variables for multiple regression) that best predicted the regression equation, ages predicted from regression equations were compared to actual age estimates with a paired two sample 1-test. In conjunction with this analysis, absolute difference statistics between predicted and actual age estimates were compared (e.g. mean, standard error, standard deviation, variance, and range).
In addition, sample data were split in half and tested for best predictive quality of regression equations as recommended by Ott (1988). Data were manipulated as follows: data sets were randomized ten times using Resampling Stats (Simon
1996), data sets were split in half, regression equations were calculated for each half-data set, reciprocal data were entered into regression equations, differences between predicted age and actual age estimates were tested using a paired two sample 1-test, regression equations were tested for coincidental regressions, and power analyses were conducted to detect a 2-year difference when null hypotheses were not rejected (Zar 1984 ). The regression equation with split data sets exhibiting (1) the most coincidental regressions (not significantly different);
(2) the least number of significant differences between predicted age and actual
age estimates; (3) conservative absolute difference statistics between predicted
age and actual age estimates (mean, standard error, standard deviation,
variance, and range); and (4) the greatest power to detect a two-year difference
was considered one of the best equations to predict age.
15 To determine whether multiple or simple linear regression predicted age best, regression statistics, residuals, and diagnostics were compared; including,
2 the aforementioned qualities, coefficient of determination (r }, standard error, cases with large leverage, outliers, residual plots of estimates, normal probability plots of residuals, and plots of Cook's distance measure (Cook 1977, Velleman and Welsch 1981, Wilkinson et al. 1992). The regression equation with the most conservative properties (or the least amount of error) was used to pool otoliths into age-groups for radiometric analyses.
To prepare otolith cores for radiometric analyses, cores were pooled into age-groups, cleaned, and dried. Age-groups were defined by sex, capture region, capture date, and age (predicted from whole otolith weight using the appropriate sex-specific regression model}. Pooled otolith cores were rough and fine cleaned following Andrews et al. (1999a, b). Cores were then dried for 48
hours in an oven at 80° C, cooled in a desiccator, and weighed to the nearest
0.0001 g.
210Pb determination
The activity of 210Pb was determined by alpha spectrometric measurement
of its alpha emitting, short-lived daughter 210Po (half-life= 138 days). All of the
otolith samples were collected more than two years before radiometric analyses
to ensure 210Po was in secular equilibrium with 210Pb (all of the 210Po activity was
16 due to ingrowth from 210Pb). Samples were prepared for 210Po analysis as described by Andrews et al. (1999a, b). Regions of interest (ROis) for each alpha-detector were determined as described by Fleer and Bacon (1984).
Separation of the two polonium peaks was usually good, but small corrections to adjust for tailing of the 210Po peal< (a small amount of 210Po counts on the low energy side of the distribution) into the 208Po region were necessary. To determine tailing of 210Po into the 208Po region, standard solutions of 210Po and
208 Po (yield tracer) were plated separately, as described in Andrews et al. (1999a, b). Tailing of 210Po in the 208Po region was calculated as a percentage of background corrected 210Po counts. Background counts in the 208Po and 210Po
ROis were determined before samples were counted, for approximately 22 days.
Reagent blank activity was negligible compared to detector background counts, therefore sample activity was only corrected for background counts. Tailing was accounted for after counts were corrected for background. Specific activity of
210Pb was calculated as follows:
Background corrected counts = counts in ROt - ( cpdbkgd *days counted) where:
counts in ROt= total counts in region of interest for either 208Po or 210Po
cpdb~ days counted= number of days sample was counted 17 Counts within the 208Po ROI were corrected for 210Po tailing. Tailing of 210Po in 208Po region was not added to the 210Po ROI, because 208Po tailing in the 209Po region was determined nor added to the 208Po ROI. 210Po counts in 208Po ROI = {210Po tailing correction)*(bkgd carr 210Po cts) Tail corrected 208Po counts = (bkgd corr208Po cts) - {210Po cts in 208Po ROI) Background and tail corrected counts were then corrected for decay during the counting time. The midpoint of the count time was calculated: where: tmid =the time in the counting interval (years), for each isotope, at which counts before and after are equal 208 2 /1 = decay constant for either Po ( ln( ) ) or 21op0 ( ln(2) ) 2.898 yr 0.3789 yr t =the time from count start to the end of the counting interval (years) Counts were then decay corrected to the time at which counting started Counts at start = (Corrected cts) * (e/..t) 18 where: Counts at start= 208Po or 210Po counts decay corrected to count start Corrected cts = 208Po background and tail corrected counts, or 210Po background corrected counts /1 = decay constant for 208Po or 210Po t =count time (years) at midpoint of 208Po or 210Po counts Activity of 210Po was then calculated with the known activity of the yield tracer and polonium counts: 21 0 Po counts] A210 = * A2oa Po [ 208 Po counts ( Po) where: 210 A 210Po =activity of Po at count start (disintegrations per minute, dpm) 210Po counts= 210Po counts at count start 208Po counts= 208Po counts at count start 208 A 208Po =known activity of Po (yield tracer) corrected to count start (dpm) The specific activity of 210 Po at count start was then calculated = _('-A_21_0p:.c:0 -'-)_ weight sample 19 where: A~ =specific activity of 210Po (disintegrations per minute per gram, dpm/g) 10Po A210Po =activity of 210 Po at count start (disintegrations per minute, dpm) weightsample =weight of clean, dry, and pooled otolith core sample (grams) The activity of 210Pb at capture was then calculated: where: A210Pb =activity of 210Pb at capture (dpm/g) 210 A210Po =specific activity of Po (dpm/g) at time of counting A226Ra =activity of 226Ra (dpm/g; determined below) 2 .:1 = decay constant for 210 Pb ( ln( ) ) 22.3 yr t =time between capture date and count start (years) Counting uncertainties were based on total counts above background for both isotopes (Wang et al. 1975}: 2 2 208 210 ~ Po ctsJ J ~ Po ctsJ [ 20Bpo cts l 210po cts 20 where: 210 a210Pb = Uncertainty of Pb activity 210 A210Pb =Activity of Pb at capture (dpm/g) 208Po cts = Background and tail corrected 208Po counts 210Po cts = Background corrected 210Po counts Samples remaining after polonium autodeposition were dried and used for 226 Ra analysis. 226Ra determination Radium-226 was measured directly using isotope-dilution TIMS at the University of California Santa Cruz (UCSC). Samples were prepared for 226Ra analysis at Moss Landing Marine Laboratories (MLML) as described by Andrews et al. (1999a, b). Uncertainty of 226Ra activity was calculated during TIMS analysis (Andrews et al. 1999b ). Radiometric age determination Radiometric age was calculated using the measured 210Pb and 226 Ra activities. For all samples, radiometric age was compensated for the ingrowth gradient of 210Pb: 226Ra in the otolith core: 21 1 -l A210Pb J A226Ra In c-~~Al tage = +T -'A where: tage = radiometric age at time of capture A Pb 210 210 =Activity of Pb at time of capture (dpm/g) A =Activity of 226Ra (dpm/g) 226Ra 2 ,.1 = decay constant for 210Pb ( ln( ) ) 22.3 yr T =core age (5 years) To compare radiometric ages with ages estimated from otolith sections, measured activity ratios for pooled otolith age-groups were plotted with expected 210Pb: 226Ra ingrowth curves. Close proximity of these data to expected ingrowth curves indicated age estimate accuracy. In addition, radiometric ages were compared directly with otolith section ages using simple linear regression and a paired two-sample t-test. 22 Growth Growth functions were fitted to partial length-at-otolith section age data for age estimates with V < 10%. Von Bertalanffy and Gompertz growth functions were fitted to length-at-age data using an iterative nonlinear least squares parameter estimation procedure with Marquardt's algorithm (FISHPARM 1989). Because no young or juvenile specimens were captured, the von Bertalanffy growth function (VBGF) was also fitted to data with to forced through zero. Simple linear regressions were also fitted to length-at-age data using a least squares procedure (Microsoft® Excel, 1994 ). Growth functions fitted to data are as follows: e-K(t-ta)) von Bertalanffy Growth Function (VBGF) PAF1 = PAF,(1- where: PAF, = Pre-anal fin length at age t PAF ro = asymptotic maximum pre-anal fin length K = instantaneous growth coefficient t = age (years) to= age at which PAF would have been zero (years) 23 Gompertz Growth Function where: PAF, = Pre-anal fin length at age t PAF0 = Pre-anal fin length at age zero G =instantaneous growth coefficient at age zero g = instantaneous rate of decrease of G Simple Linear Regression PAF1 = mt+ b where: PAF, = Pre-anal fin length at age t m = slope of line t = age (years) b = y-intercept of line To determine which growth curves fit data best, confidence intervals, coefficient 2 2 of determination (r or adjusted r , Kvalseth 1985), mean square error (MSE), and the number of iterations required to meet convergence criteria were compared, and growth parameters were examined. Growth curves that fit data best were chosen to describe fish and otolith growth. 24 To compare published A. pectoralis age and growth estimates to this study, von Bertalanffy growth functions were fitted to published average length at-age data. Prior to fitting growth curves to published data, total lengths were converted to pre-anal fin lengths using the partial length regression equations calculated in this study. The von Bertalanffy growth function was also fitted to radiometric age and mean PAF data for pooled otolith age-groups using FISHPARM (1989). Because no young or juvenile specimens were captured, the VBGF was also fitted to data with to forced through zero. RESULTS A total of 1,127 Albatrossia pectoralis was collected off the Aleutian Islands, Alasl October 1997 (Tables 1 and 2, Fig. 2). Specimens were captured from depths between 348 and 1 ,290 m. Eighty-three percent of all specimens were captured off Alaska and Oregon. Albatrossia pectoralis specimens collected during research cruises were used for all analyses, while specimens captured by commercial fishermen were used for length frequency and age estimation analyses only. Males and females were analyzed separately. Immature (or sex undetermined) individuals were used in a "sexes combined" category. 25 Partial length analysis Grenadiers with intact tails were not always available. Specimens collected southeast of Kodiak, Alasl 1995, and April 1996, however, had intact tails (n = 136). Three lengths were measured from fresh specimens: head length, pre-anal fin length, and total length (Fig. 1 ). Total length was correlated with pre-anal fin length for males, females, and sexes combined (Fig. 3). The regression equations for males and females were not significantly different (F0.05111 .2.131 = 3.06, F,1a1 = 0.01, P > 0.05). Therefore, a single regression can estimate total length from pre-anal fin length for the sexes combined. The slope of the combined regression was significantly different from zero {F005111.1•134 = 3.91, F,,a,= 1707.50, P < 0.00, MSE = 12.66). Pre-anal fin lengths used to construct the combined regression ranged from 18 to 50 em. Total length was also correlated with head length for males, females, and sexes combined (Fig. 4). The regressions for males and females were not significantly different (F005111•2•131 = 3.065, F,1a1= 0.3173, P > 0.05). A single regression, therefore, can estimate total length from head length for the sexes combined. The slope of the combined regression was significantly different from zero (F005111.1.134 = 3.91, F,1a1 = 860.36, P < 0.00, MSE = 23.45). Head lengths used to construct the combined regression ranged from 10 to 25 em. 26 Although total length can be predicted from pre-anal fin length or head length, pre-anal fin length will be used for further age and growth analyses. A greater proportion of the total variation in total length was accounted for by the fitted regression with pre-anal fin length. As with any regression, it is advised that only the observed range of pre-anal fin lengths used to construct such a regression be used to calculate total length. The sampling gear used to collect specimens was different for all collecting agencies. Therefore, statistical tests were not used to test for size differences between the sexes or regions; only descriptive statistics were calculated. Research cruise and commercial catch data were combined to describe mean partial length and range. A total of 1,123 A. pectoralis was used to describe length frequency distribution between the sexes and regions. Overall, females (x= 26.5 ± 0.3 em PAF, n = 710) were larger than males (x= 22.1 ± 0.3 em PAF, n = 406); sex or PAF data were not available for seven individuals. The smallest specimen was a male (1 0 em PAF) captured off California between 1,108 and 1,130 m during an AFSC slope survey; the largest specimen was a female (25 kg, 61 em PAF) captured off Oregon between 1,244 and 1,281 m by a commercial fisherman (Fig. 5). No males were captured off the Aleutian Islands. Mean PAF was greatest in the Aleutian Islands region, followed by Alaska, California, and Oregon. Females were larger than males off Alaska, Oregon, and California. 27 Otolith size and fish length analysis Otolith height and thickness were difficult to measure. The ventral surface of otoliths was characterized by numerous irregular crenulations, which were prone to breakage (Fig. 6). When otoliths were intact, locating a maximum height along the dorsal-ventral axis was subjective and rarely perpendicular to the anterior-posterior axis. These otolith height characteristics often rendered measurement impossible or extremely variable among repeated measurements. Otolith thickness could not be measured easily with the image analyzer, and could not be resolved to less than ± 0.1 mm with dial calipers. As a result, there was no variability between otoliths to describe growth along the distal-proximal axis. Consequently, otolith height and thickness measurements were extremely subjective and variable among repeated measurements. These two measurements were therefore omitted from analyses. Whole intact otoliths from male and female specimens collected off Oregon during 1993 were used for otolith pair difference analyses. There was no significant difference between left and right otolith length {t005<2 >. 122 = 1.980, t,,a, = 0.920, P = 0.359). Similarly, there was no significant difference between left and right otolith weight (t005(2). 105 = 1.983, t,,a, = 0.244, P = 0.808). Because there was no difference between left and right o~oliths, either otolith was used for further analyses. 28 Otolith length increased linearly with pre-anal fin length for males, females, and sexes combined (simple linear regression, Fig. 7). The regressions for males and females were not significantly different {F005111,2,466 = 3.01, F,,,, = 1 .66, P > 0.05). Therefore, a single regression can describe the relationship between otolith length and pre-anal fin length for the sexes combined (Fig. 7). The slope of the linear regression for the sexes combined was significantly different from zero (F0.05111,1.4 70 = 3.86, F,181 = 1870.19, P < 0.00). Pre-anal fin lengths used to construct the combined regression ranged from 14 to 44 em. Otolith weight increased non-linearly with pre-anal fin length for males, females, and sexes combined (allometric growth function; Fig. 8). Allometric growth functions for males and females were not significantly different (F0.05111,2.4 68 = 3.01, F,181 = 1 .52, P > 0.05). Therefore, a single allometric growth equation can describe the relationship between otolith weight and pre-anal fin length for the sexes combined (Fig. 8). The allometric growth function for the sexes combined was statistically significant {F0.05111,2,472 = 3.01, F,1a1 = 5025.84, P < 0.00). Pre-anal fin lengths used to construct the combined regression ranged from 14 to 44 em. Otolith length and weight increased with fish size (as described by pre anal fin length). As with any regression, it is advised that only the observed range of pre-anal fin lengths used to construct the linear regression equation and allometric growth equation (non-linear regression) be used to calculate otolith length or weight, respectively. Although otolith weight and length increased with 29 pre-anal fin length, a greater proportion of the total variation in otolith weight was accounted for by the fitted allometric growth function with pre-anal fin length (r 2 = 0.83). Age estimation Four hundred eighty-six otoliths were sectioned, of which 357 were read five times by Reader 1. One hundred twenty-nine otoliths (26.5%) were unreadable or rated as "bad". Otoliths in this category were either ground too thin (past the plane of the nucleus) or sectioned obliquely; rendering incomplete or obscure increments. Growth increments were difficult to interpret. Prior to counting increments, an otolith section was inspected for a regular growth pattern from the otolith center to the outer margin at 31.5 to SOx magnification. Growth increments along the dorsal-ventral axis were often irregularly spaced, ceased in larger otoliths, and continued along the proximal-distal axis on the both sides of the sulcus acousticus (proximal face; Fig. 9). Growth along the proximal-distal axis was narrow and irregularly spaced at the otolith center and intermediate areas, but regular and easily quantified on the proximal face when dorsal-ventral growth ceased. Therefore, growth increments were counted along the dorsal-ventral axis from the center to intermediate areas until otolith growth appeared regular along the proximal-distal axis (:=15 to 20 increments), where increments were 30 counted on the proximal face. A growth increment was quantified as a pair of opaque and translucent (hyaline) zones. Most otolith sections were rated as fair. In age determination studies, age is commonly estimated 2 to 3 times to assess the reproducibility or precision of age estimates (Beamish and Fournier 1981, Chang 1982, Kimura and Lyons 1991, Campana et al. 1995). After three readings, however, age estimates were still quite different, which made final age assignments suspect. Therefore, two additional readings were included. Final age estimates for all otoliths (n = 357) ranged from 13 to 56 yr. Percent agreement among five readings for Reader 1 was low; while precision of age estimates was satisfactory (Table 3, Fig. 10). The difference between age estimates ranged from 0 to 32 yr with a mean difference of -0.8 yr. The maximum difference of Reader 1 age estimates (32 yr) approached the maximum age estimate (56 yr). Greater than 72% of age estimates were within ± 5 increments; 94% were within± 10 increments. Overall, the average percent error (APE) was 9.52%, the coefficient of variation (V) was 12.53%, and the average index of precision (0) was 5.60% (n = 357). Using the average index of precision (0), ageing error was 0. 7 yr for a 13 yr age estimate and 3.1 yr for a 56 yr age estimate. Ageing precision of males and females was similar. Age estimates with V s 10% ranged from 17 to 49 years; these age estimates were used for fitting length-at-age growth curves (n = 139) and otolith weight-at-age growth curves (n = 136). 31 For age-specific precision analysis, five-year age-group categories were arbitrarily established to compare ageing error with increasing age estimates (Table 3). The youngest and oldest age estimates were grouped into 2- and? year age-group categories, respectively. These different age categories were a result of lone age estimates and the inability to pool samples into 5-yr age-groups categories. Otolith weight range overlapped among the age-group categories. Average otolith weight, however, increased with increasing age, except for the 45 to 49 yr age-group. Percent agreement of readings tended to decrease with increasing age. Percent agreement of age estimates within ± 5 increments ranged from 40.0% to 80.5%. Ageing error (APE, V, and 0) tended to decrease with increasing age, except for the two oldest age-groups. From the random subset of fifty otolith sections, precision (0) of Reader 1 age estimates (4.9%) was greater than that of Readers 2 (7.5%) and 3 (6.9%). Seventy-four percent of Reader 1's age estimates were within ± 5 increments. Percent agreement within ± 5 increments for Readers 2 and 3 was lower than Reader 1; 66.7% and 61.3%, respectively. Age estimates between Readers 1 and 2 were more similar than other reader comparisons; 70% of age estimates were within ± 5 increments (Fig. 11 ). Ageing error was greatest, and precision lowest between Reader 3 and the other two readers. Reader 3 was unable to determine age for 6 samples, therefore only 44 samples were included in his precision analysis. Age bias plots illustrate 32 this trend more clearly (Fig. 12). Age estimates between Readers 1 and 2 lie closer to a line of agreement and exhibit less error than other reader comparisons. In addition, the age bias plot illustrates that there are no systematic age differences between readers (i.e. consistently over- or under estimating age). Radiometric analysis Radium e26 Ra and 228 Ra) was measured in whole A. pectoralis otoliths (n = 6; Table 4). Radium-226 activities ranged from 0.0292 to 0.0422 disintegrations per minute per gram (dpm/g). Negligible quantities (below background) of 228Ra were present in whole otolith samples; therefore, 228Ra could be used as a yield tracer, and accurate 226Ra detection was possible. Radium determination was successful for samples weighing 0.457 to 0.804 g. Core extraction and age-group determination Otolith core dimensions from 22 adult sectioned otoliths were determined to be 3.5 mm wide, 1.0 mm high, and 0.5 mm thick. Individual otolith cores weighed 8.0 mg; therefore, approximately 62 otolith cores had to be pooled to form a 0.5 g sample. Male and female ages (log transformed) were best predicted from the log of otolith weight using simple linear regression models. Multiple regression 33 models did not predict age better than simple linear regression. Only final linear regression equations are presented here. The ranges of otolith weight used to construct regression equations were 0.027 to 0.327 g for males (n = 35) and 0.040 to 0.494 g for females (n = 7 4 ). Consequently, only otoliths within these specific weight ranges were pooled into age-groups. Male and female age was predicted from otolith weight using the following linear regression equations: Males log(age) = (0.307) * [log(otolith weight)]+ 1.7 49Adj r 2 = 0.65 Females log(age)= (0.293)*[/og(oto/ith weight)]+ 1.711 Adj r 2 = 0.73 Low and high predicted age estimates were calculated from regression equation statistics (95% confidence intervals). Otoliths were pooled into age-groups based on sex, general capture location, capture date, and whole otolith weight (i.e. regression predicted ages). Twelve adult age-groups (5 male and 7 female) were assembled for radiometric analysis (Table 5). Male and female predicted ages ranged from 20 to 35 years. The difference between capture dates for a pooled sample ranged from 1 to 20 days. At least 29 fish were included in each sample. In the smallest sample (AP-18), both otoliths were used from each fish (58 cores). The sample containing the greatest number of fish (AP-19), included 63 fish and 63 otolith cores; one otolith from each fish. Sample AP-12 contained the greatest number 34 of otoliths (86 cores), comprising 45 fish. Cored and cleaned samples weighed less than the recommended 0.5 g, and ranged from 0.2820 to 0.4463 g. Because ages of the pooled groups were based on linear regression models of otolith weight and otolith section age estimates, there was little to no overlap of whole otolith weight between age-groups. 210Pb and 226Ra determination Radiometric measurements are expressed as specific activities (disintegrations per minute per gram, dpm/g) and as activity ratios (Table 6). The activity of 226Ra ranged from 0.0463 to 0.0694 dpm/g (n = 12); x= 0.0578 ± 0.006 dpm/g (± s). Lead-21 0 activity for eleven samples ranged from 0.020 to 0.033 dpm/g. One sample (AP-11) had a 210Pb activity much greater than what could be explained by radium decay (0.069 dpm/g) and was considered an outlier. The lowest 210Pb activity was from one of the youngest predicted age-groups (20 to 25 yr; sample AP-17). The outlying sample (AP-11) had the highest 210 Pb activity and was one of the oldest predicted age-groups (31 to 35 yr). The sample with the second highest 210 Pb activity was one of the youngest predicted age-groups (20 to 25 yr; sample AP-16). Activity ratios tended to increase with increasing age of predicted age groups (Table 6, Fig. 13). One of the youngest predicted age-groups (male, 2·1- 25 yr; AP-15) had the lowest activity ratio (0.340 dpm/g). The oldest predicted 35 age-group (female, 31-35 yr; AP-12) had the highest activity ratio (0.598 dpm/g). Sample AP-11 had an activity ratio greater than 1.0; a ratio where radiometric age cannot be determined. There were no obvious trends between initial uptake ratio and predicted age, or capture location. Four female activity ratios, however, surrounded and closely fit an Ra =0.0 (Fig. 13; Samples AP-9, 10, 12, and 19). Activity ratios for eight of the twelve samples occurred below an initial activity ratio of 0.0; two samples were between 0.0 and 0.1; and one sample was between 0.1 and 0.2. Sample AP-11 occurred well above an initial activity ratio of 0.2. This is an unexplained result in addition to its observed activity ratio greater than 1.0. As a result, sample AP-11 was not plotted. Radiometric age determination A direct comparison of predicted ages (from otolith weight) and radiometric ages resulted in a scatter of data points on either side of a line of agreement (Fig. 14). Most data points fell below a line of agreement, indicating predicted ages were older than radiometric ages. The regression of predicted and radiometric ages fit data poorly (r 2 = 0.272). All age-groups considered, predicted ages and radiometric ages were significantly different (paired-sample t test, 1005121 ,10 = 2.228, t, 181 = 2.517, P = 0.031). 36 Radiometric and predicted ages agreed (occurred within ranges of uncertainties) for 6 of the pooled age-groups (Fig. 14 ). The predicted age range for 4 female samples (AP-9, 10, 12, and 19), and 95% confidence intervals for 2 additional samples (AP-8, female; AP-16, male) intersected a line of agreement. Otolith section ages were confirmed for these six samples. Radiometric age determination confirmed longevity to at least 32 years for females and 27 years for males. Growth Von Bertalanffy growth functions were ineffective summaries of PAF-at otolith section age data; there was excessive variability around VBGF parameters (Table 7). Confidence intervals for growth parameters were greater 2 than calculated values, and coefficients of determination (adjusted r ) were less than 0.64. Many iterations were required to meet convergence criteria for males and the sexes combined during regular VBGF computations. Due to the lack of fit, growth parameters are presented without plotting growth curves. Von Bertalanffy growth parameters were not similar between the sexes (Table 7). Computation of the VBGF for males resulted in an extremely large ). asymptotic pre-anal fin length (PAF00 The initial estimate of PAFm was equal to the maximum constraint of the FISHPARM starting parameter matrix (38,000). When the maximum constraint was manipulated, PAFW continued to increase and 37 could not be resolved due to the linearity of data (Fig. 15). As a result, the growth coefficient (K) was extremely small (i.e. predicted growth would be extremely slow to approach PAF~). Results for males in Table 7 are from the initial computation. When to was held constant at zero, VBGF growth parameters were considerably different than regularly computed parameters. Male PAF~ was less than, and K was greater than, VBGF parameters calculated during regular computation (Table 7). Female PAFOO and K, however, increased. Standard errors for VBGF parameters could not be computed when to was held constant at zero (FISHPARM 1989); therefore, confidence intervals were not calculated. Many iterations were required to meet convergence criteria for females and the sexes combined. Regular VBGF and to forced through zero computations fit data 2 similarly; the coefficient of determination (adjusted r ) and mean square error (MSE) were similar among sexes when the two computations were compared. Gompertz and linear regression growth functions also suffered from lack 2 of fit to data (Table 8). Coefficient of determination values (r ) were less than 0.65, and confidence intervals were similar in magnitude or exceeded growth parameters. As with otolith section ages, von Bertalanffy growth functions were ineffective summaries of PAF-at-radiometric age data; there was excessive variability around VBGF parameters (Table 9). Confidence intervals for growth 38 parameters were greater than calculated values, and coefficients of 2 2 determination (adjusted r ) were less than 0.24. Negative adjusted r values indicated the VBGF exhibited lacl< of fit (Saila et al. 1988). Many iterations were required to meet convergence criteria. Due to the lacl< of fit, growth parameters and mean PAF-at-radiometric age data are presented without plotting growth curves (Table 9, Fig. 16). Forcing to through zero improved growth parameter estimates (i.e. more realistic values). The fit of the VBGF to data, however, remained poor. DISCUSSION Small or juvenile fish (<10 em PAF) were absent from bottom trawls. Juvenile A. pectoralis are thought to be pelagic for an extended growth period, at the end of which they mature and settle on the continental slope (Marshall 1965, Novil are shed and fertilized near the bottom and develop as they slowly float upward through the water column. Larvae hatch at 200 m or deeper (at the seasonal thermocline). and then the young sin I< downward and settle on the bottom as adults. Novil descend to demersal layers only after reaching a length of 50 to 60 em TL. In the North Pacific, Novil 50 em (TL; mature). except in the Sea of Ol 39 individuals were captured on the bottom along with adults. He speculated that the hydrographic regime and the broad continental slope of the Sea of Okhotsk were responsible for lower fish density than in other regions. Albatrossia pectoralis larvae from the California Current and alevins from the northern North Pacific have been described (Ambrose 1996, Endo et al. 1993). Unfortunately, capture of juveniles in the eastern North Pacific is rare (Tomio Iwamoto, California Academy of Sciences, Golden Gate Pari<, San Francisco, CA 94118, personal communication) or unknown (David Ambrose, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, CA 92038, personal communication). One such rare individual (23 em TL), identified by T. Iwamoto as Coryphaenoides pectoralis, was captured off Canada at <1 ,500 m depth (Peden et al. 1985). In this study, females were more abundant than males. The sex ratio of A. pectoralis in the North Pacific changes with depth; females occur at shallower depths, whereas males occur deeper (Novikov 1970, Tuponogov 1986). Novikov (1970) noted that females occurred between 300 and 700 m, and males occurred >700 m while most trawling effort occurred at depths <800 m. Tuponogov (1986) found that females predominated at depths <1 ,000 m, while the proportion of males increased at deeper depths. It is possible that the greater number of females captured during this study was a result of trawling depth. The shallower trawling areas, which occurred off the Aleutian Islands and Alaska, were primarily 40 female-based catches. The depth range off Oregon was wide (478 to 1,250 m) and the sex ratio was more evenly distributed than at other locations. Partial length analysis The most appropriate partial length measurement for A. pectoralis is pre anal fin length; total length could be predicted from pre-anal fin length with less variation than from head length. Andrews et al. (1999a) demonstrated three partial lengths (PAF, HL, and snout to dorsal fin) could be used to determine TL for C. acrolepis, but PAF was the best TL replacement. Atkinson (1991) found no significant difference between male and female partial length regression equations forM. berlax; therefore, a single equation was appropriate. For C. rupestris, partial length regression equations were significantly different between the sexes, but the difference was less than the measurement criteria so separate equations were ignored (Atkinson 1981 ). Andrews et al. (1999a) did not differentiate between the sexes. Otolith size and fish length analysis Otolith morphometries are often correlated with fish size (Hecht and Appelbaum 1982, Harkonen 1986). To find the best possible correlation, it is important to choose a practical size parameter of the otolith (Harkonen 1986). Otolith length is the largest one-dimensional parameter which minimizes the error 41 of measurement. Pointed irregular ends, however, could create problems and lower the correlation coefficient. In this study, anterior and posterior ends of A. pectoralis otoliths were fairly regular, and otolith length correlated well with pre anal fin length. Otolith width, the second largest one-dimensional parameter, could yield better correlations due to less variable shape of the dorsal and ventral margins. In the case of A. pectoralis, otolith width was problematic due to irregular crenulations on the ventral margin (Fig. 6). Otolith thickness, the smallest parameter, increases the error of measurement and can be an important source of error. Otolith thickness was omitted from analysis in this study, because the small measurement was variable among repeated measurements and did not describe fish size. When measuring otolith weight, a three dimensional parameter, variable structures of the otolith are less important, and the error of the measurement depends mainly on the quality of the measuring device (i.e. the scale or balance). In this study, otolith weight correlated best with pre-anal fin length. In addition, the irregular shape of A. pectoralis otoliths rendered otolith weight a more dependable and more easily obtainable measurement than otolith length, height, or thickness. Close fit of the allometric growth function to otolith weight and PAF data described fish growth in terms of otolith growth; as a consequence, otolith weight was used to predict age and pool otoliths for radiometric analysis, which will be discussed later . 42 Age estimation Age estimates indicated A. pectoralis is slow growing and lives as long as 56 years. Difficulty interpreting growth increments, however, created a lack of confidence in age estimates. Interpreting the first 15 to 20 growth increments along the dorsal-ventral axis was difficult, because of irregular spacing. I suspect checks were present within this area, and contributed to the irregular appearance of increments and difficulty estimating age. These checks may reflect differential otolith deposition due to movement in the water column prior to settlement. In 1 contrast, increment patterns on the proximal face (>20 h increment) were clear, regularly spaced, and easily quantified. Fine bands between increments along the dorsal-ventral axis in otoliths have been observed in other species (Chilton and Beamish 1982, Kelly et al. 1997). Such bands are usually identified as checks, and are not included in age estimates. In this study, increments counted along the dorsal-ventral axis were confusing, and checks could not always be differentiated from regular growth increments. Therefore, checks were likely included in age estimates, possibly over-estimating age. Intra-reader precision varied among age-groups. Surprisingly, precision improved with increasing age estimates. The low precision for younger age groups (13 to 19 yr) could have been a consequence of incorrectly interpreting 11 increments and checks along the dorsal-ventral axis (<20 ' increment), which is a 43 likely source of error when counting increments for these younger age-groups. It is also possible that bias existed when ageing larger otoliths. Stacked growth increments on the proximal face were obvious in larger otoliths and probably contributed to a preconceived notion (or bias) that such otoliths were older. Consequently, these otoliths were probably consistently assigned older ages. Precision was low for the oldest age group; which could be a result narrowly spaced increments at the otolith margin, which were difficult to read. Between-reader precision of age estimates from other difficult-to-age or long-lived species was similar to or greater than precision in this study. Kelly et al. (1997) estimated age of C. rupestris using transverse otolith sections (2 to 60 yr). The APE between two readers (4.9% for ages 1 to 58 yr) was less than this study (7.6 to 13.7%) and percent agreement within± 5 years (75%) was greater than this study (40.9 to 70.0%). Using transverse otolith sections, Andrews et al. (1999a) estimated age of the C. acrolepis (2 to 73 yr). The APE between two readers was 6.3% and percent agreement within± 5 years was 80%. The coefficient of variation ( V) between two readers for break-and-burn sablefish (Anoplopoma fimbria) otoliths was 12.9% for fish aged 1 to 29 yr (Kimura and Lyons 1991); within the range of Vbetween readers in this study (10.7 to 19.4%). 44 Radiometric analysis Radium-226 activities in adult A. pectoralis otolith cores (0.0578 ± 0.006 dpm/g; ± s, n = 12) are comparable to other species inhabiting the continental slope. For example, adult C. acrolepis otolith cores had a mean 226Ra activity of 0.0560 ± 0.0101 dpm/g (± s, n = 6; Andrews et al. 1999a); whole juvenile and adult A. verrucosus otoliths had a mean 226Ra activity of 0.0533 ± 0.0086 dpm/g (± s, n = 11; Stewart et al. 1995); whole juvenile and adult splitnose rockfish (Sebastes diploproa) otoliths had mean 226Ra activities of0.043 ± 0.009 dpm/g (± s, n = 4; Bennett et al. 1982); and whole juvenile and adult shortspine and longspine thornyhead ( Sebastes alascanus and S. a/live/is) otoliths had mean 226Ra activities of 0.043 ± 0.006 dpm/g (± s, n = 3) and 0.045 ± 0.002 dpm/g (± s, n = 7), respectively (Kline 1996). Age estimates for approximately half of the pooled age-groups were validated using radiochemistry. This was illustrated with predicted ages plotted with expected ingrowth curves (Fig. 13), and by direct comparison of radiometric and predicted ages (Fig. 14 ). Data points that fell along expected ingrowth curves indicated age estimate accuracy. The deviation of data points from expected ingrowth curves is probably a result of imprecise predicted age estimates, rather than significant 210Pb at initial incorporation. Initial activity ratios in juvenile otoliths could not be measured because small fish were not collected. By using otolith cores, it was assumed that all juveniles accumulate 210Pb and 45 226 Ra in a constant ratio. If 210 Pb had been significant at initial incorporation, data points would have been scattered above expected ingrowth curves. Although it is uncertain why the 210Pb: 226Ra activity ratio in sample AP-11 exceeded 1.0, incorporation of exogenous 210 Pb (or 210 Po), or contamination during sample processing are possible explanations. Several sources of error were involved in constructing otolith core groups: ("I) age estimate precision, (2) the regression equation of otolith section age and otolith weight, (3) the estimated 5 yr core size, and of course (4) age estimate accuracy. When predicted ages were compared to radiometric ages, however, only the error associated with the predictive age equation was incorporated. In addition, the fit of the regression to otolith weight and section age data was less than optimal. Therefore, the error associated with predicted age was actually quite larger than presented. As a result, It is possible that most, if not all, of the predicted age-groups would have agreed with radiometric ages. Ultimately, this imprecision can be attributed to the difficulty interpreting growth increments found in otoliths. The predictive age equation for females was a better fit than the male equation. This may have contributed to better agreement between female ages. Age agreement of several age-groups indicated that A. pectoralis collected during this study were middle-aged fish (~22 to 32 yr). Longevity likely exceeds the oldest radiometric age estimates. Larger fish and older age estimates were 46 available, but could not be radiometrically analyzed because of the lack of otolith material required for analysis. Growth The von Bertalanffy growth function (VBGF) for A. pectoralis produced curves (VBGCs) that did not fit PAF-at-age data well. The poor fit can be attributed to the difficulty and variability of counting growth increments in otoliths. Male age and length data appeared linear, whereas female length at middle-ages (17 to 38 yr) appeared linear, but at older ages deviated from linearity and exhibited greater variability. Consequently, VBGF parameters were not readily accepted. Asymptotic PAF (PAFcx; 506 em for males; 90 em for females) was greater than maximum pre-anal fin lengths observed in this study (50 em for males; 61 em for females) and corresponding maximum TL in the literature (:o:150 em TL, =58 em PAF; Rass 1963, Novikov 1970, Iwamoto and Stein 197 4 ). Although PAF"' exceeded observed lengths, PAF"' for females was more reasonable than for males. If the relationship between PAF and TL follows a linear growth pattern beyond the maximum PAF used to calculate TL in this study, TL would be 219 em; well beyond the published maximum total length of 150 em (Iwamoto and Stein 197 4 ). The growth coefficient for female A. pectoralis (K = 0.015) was less than that observed for otolith ageing studies of macrourids and other deep-sea fishes: 47 female C. acrolepis (K = 0.024, Andrews et al. 1999a); female C. rupestris (K ~ 0.1 00; Bergstad 1990, Kelly et al. 1997); Al/ocyttus verrucosus (warty oreo, K = 0.056, Stewart et al. 1995); and Hoplostethus at/anticus (orange roughy, K = 0.06, Smith et al. 1995). In contrast, Savvatimsky (1994) estimated age of female M. berg/ax using scales and calculated a VBGF growth coefficient similar to A. pectoralis (K = 0.014). Age estimates forM. berg/ax did not exceed 22 years, growth appeared linear, and Tloo was almost three times the maximum observed or published total length. He noted the difficulty in ageing scales from larger fish, and proposed that rings within the central part of scales may each constitute 1-2 years. Small or juvenile individuals were absent from this study; therefore a dependable or accurate estimate of to was not possible. When to was forced through zero, male VBGF parameter estimates improved, but remained unreasonable (1 06 em PAF w ~254 em TL). In addition, curves did not fit data better than regular VBGF computations, as judged by the comparison of 2 coefficients of determination (adjusted r ) and mean square errors (MSE) among the sexes. All previously published A. pectoralis age estimates were determined using scales (Kulikova 1957, Novikov 1970, Pautov 1975, Tuponogov 1997). The oldest age estimates of A. pectoralis from this study were 3 to 6 times greater than published ages at similar lengths. Kulikova (1957) reported a maximum age 48 of 8 yr at 96 em TL; whereas Novikov (1970) and Pautov (1975) reported ages twice as old at similar lengths ( 15 to 17 yr at ::=93 em TL and 17 yr at 115 em TL, respectively). Tuponogov (1997) estimated 23 yr of age for a fish close to maximum recorded length (::=150 em TL}. Average length-at-age data were provided in Kulil Bertalanffy growth functions. A comparison of von Bertalanffy growth functions fitted to A. pectoralis age estimates from Kulikova (1957), Pautov (1975), and this study revealed major growth differences (Fig. 17). Only females from this study were compared to published estimates, because of the extremely poor fit of the VBGF to male data in this study. Pautov (1975) aged only females, whereas Kulikova (1957) did not differentiate between the sexes. Differences in growth functions can be attributed to the difference in structures used to estimate age (scales and otoliths}, and the difficulty and variability in estimating age from otoliths. Growth rates from the two published studies were fast and showed signs of approaching maximum length quickly. The VBGC fitted to Kulikova's (1957) data was almost linear and did not demonstrate slower growth at larger sizes. Ages estimated by Pautov (1975) were twice those of Kulikova's (1957) estimates, and the VBGC showed signs of slower growth as fish approached maximum length. The VBGC for females in this study was practically linear, and the growth coefficient (K) was ::=11 times less than published estimates. The 49 difference between growth rates of published studies and the current study can be attributed to the older age composition in the current study (17 to 49 yr; i.e. it takes a longer time to attain a similar maximum length when longevity is greater). In the published studies, to was closer to zero than in this study. The lack of small fishes available to determine age in this study, resulted in difficulty anchoring the von Bertalanffy growth cuNe at zero; which contributed to a larger . estimate of t0 Asymptotic lengths (PAFro) among the published studies were similar, and half the PAFro value estimated in this study. Asymptotic lengths (PAF "')for the published studies are comparable to maximum recorded lengths (~150 em TL, =58 em PAF; Iwamoto and Stein 1974). The difficulty and variability in estimating age from otoliths in this study, especially at older ages, contributed to the overestimation of PAF~ Published age and longevity estimates of A. pectoralis using scales are unverified and unvalidated. In addition, scales can be unreliable structures for age determination (Simkiss 197 4, lchii and Mugiya 1983, Beamish and McFarlane 1987). Little confidence, therefore, can be attributed to past age estimates. Longevity determined in this study using otolith sections (56 yr) was two to seven times greater than that determined in other studies using scales (8 to 23 yr). Using otoliths to determine age with traditional and radiometric methods should provide more accurate age and longevity estimates. 50 Neither the Gompertz growth function nor simple linear regression 2 described growth better than the VBGF; coefficients of determination (r ) and mean square errors (MSE) were similar to those calculated for the VBGF. It is not surprising that a Gompertz growth function did not fit data better than the VBGF, because only the portion of the curve beyond the inflection point is involved (Ricker 1975). Because data did not resemble an S-shaped curve and lacked an upper asymptote, the poor fit was similar to the VBGF. Although male PAF-at-age data appeared linear, the simple linear regression lacked goodness of fit; only 58% of the total variation in PAF could be accounted for by the fitted regression. The majority of specimens collected during this study were mature and of intermediate sizes, and estimated as middle-aged fish. Despite the majority of intermediate-size fish, the difficulty in reading otoliths probably contributed to the inclusion of precise middle-aged age estimates ( V < 10%) and the exclusion of less precise younger and older age estimates in growth analysis. Therefore, age estimates included in growth function analysis may have been biased towards middle-aged fish. The lack of older age estimates at greater lengths made fitting of the VBGF (or Gompertz) difficult. In addition, variability of female PAF at older ages complicated curve fitting. The VBGF fitted to radiometric age and mean PAF data was not much of an improvement from the VBGF fitted to estimated age and PAF data. Despite 51 the poor fit, the VBGF where to was forced through zero resulted in more reasonable growth parameters. Asymptotic total lengths (calculated from PAF) were 84 em for males, and 153 em for females. Growth coefficients (K} were also comparable to other macrourids. Fishery Albatrossia pectoralis is one of the most abundant grenadier species found along the continental slope of the North Pacific (Novikov 1970; Pautov 1975; Tuponogov 1986, 1997). Tuponogov (1986) indicated the biomass of A. pectoralis could yield the most promising deep-sea fishery in the Soviet economy zone. During non-selective trawling off the northern Kuril Islands from 1982 to 1984, A. pectoralis comprised 60 to 70% of the total catch, with Coryphaenoides cinereus and C. acrolepis captured as well. When targeting A. pectoralis, it comprised 95 to 98% of the total catch. Similarly, A. pectoralis comprised 97% of the total macrourid biomass (382,837 metric tons) during research surveys from June through November 1980 in the Aleutian Islands region; where 96% of A. pectoralis inhabit 501 to 900 m depths, and 4% inhabit 301 to 500 m (Ronholt et al. 1986). The total population of A. pectoralis was estimated to be =140 million fish, of which 93.5% occurred in the Aleutian region, 6% in the western Shumagin subarea, and <1% in the southern Bering Sea subarea. In comparison to other stocks, A. pectoralis had the highest estimated biomass in 52 the Aleutian region, followed by walleye pollack (Theragra chalcogramma), Atka mackerel (Pieurogrammus monopterygius), Pacific ocean perch (Sebastes alutus), and Pacific cod (Gadus macrocephalus). The distribution of Albatrossia pectoralis is sex specific and may be seasonal in some areas. Male and female A. pectoralis live separately; females are found at shallower depths than males (300 to 700 m), and migrate to deeper waters during autumn and winter when their ovaries ripen (Novikov 1970). It is also thought that grenadier migrate to shallower depths during spring and summer to spawn for brief periods, when the cold intermediate layer is destroyed by warm oceanic waters (Novikov 1970, Tuponogov 1997). In the Sea of Okhotsk, these limited seasonal migrations during the summer on the continental slope result in peak concentrations of A. pectoralis (Tuponogov 1986, 1997). During summer trawl surveys off the northern Kuril Islands in the western North Pacific, at depths between 500 to 700 m and 900 to 1 ,000 m, A. pectoralis formed significant concentrations of up to 50 tons per square mile (Tuponogov 1997). The greatest concentrations, up to 65 to 150 tons per square mile, occurred at 1000 to 1300 m off Paramushir, Onekotan and Karimkotan islands. The area of these concentrations, during the summer, was about 700 square miles. Aggregations of A. pectoralis observed in the Sea of Okhotsk (<1 to 5 tons per square mile), however, do not necessarily occur throughout its range. During winter, concentrations are less dense and occur 100 to 200 m deeper 53 than during the summer. Dense concentrations of A. pectoralis during summer months may support a target fishery in specific geographic areas. A major fishery targeting A. pectoralis has yet to be developed. A small fishery exists off California for C. acrolepis and is somewhat dependant upon the sablefish fishery (Leos 1998, Andrews 1999a). Albatrossia pectoralis is captured with C. acrolepis, but comprises an insignificant portion of commercial grenadier landings (Bob Leos, California Department of Fish and Game, 20 Lower Ragsdale Drive, Suite 100, Monterey, California 93940, personal communication). In contrast, A. pectoralis is the most abundant grenadier species captured in the Gulf of Alaska (Charles Crapo, personal communication). The flesh of A. pectoralis, however, is soft and unacceptable for human consumption (Matsui et al. 1990). Crapo et al. (In Press) investigated treatments to improve the texture of A. pectoralis flesh. Incremental improvements were made using food protein solutions and high salt concentrations, but the texture improved only slightly. Research continues to improve the marketability of A. pectoralis fillets. One company in Kodiak, Alaska, however, targets A. pectoralis and sells fillets to France, where there is a market for soft fleshed fish (Charles Crapo, personal communication). Age-at-maturity in this study can be estimated from length-at-maturity data from other studies. Albatrossia pectoralis reach sexual maturity at 50 to 56 em TL, when settlement occurs (Novikov 1970). Based on the von Bertalanffy 54 growth function fitted to otolith increment ages in this study, sexual maturity for females occurs at 14 to 16 yr. For female radiometric ages where to = 0, sexual maturity occurs at 10 to 13 yr. Using scales, Novil (1997) estimated 8 to 11 yr (50% mature). Because sexual maturity of A. pectoralis is associated with timing of settlement, juveniles are not directly vulnerable to the trawl fishery. Protection of the egg, larval, and juvenile phases, however, is important to the supply of recruits to the adult population. Unfortunately, these early life history phases are poorly l Age estimates for several A. pectoralis size classes, necessary to develop a sound fishery management plan, remain questionable. Radiometric age determination, however, confirmed otolith increment ages for several pooled age groups (::=22 to 32 yr), and that growth increments found in otoliths are difficult to interpret. 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In: T.B. Bagenal (Editor). The Ageing of Fish. Proceedings of an International Symposium. Unwin Brothers Limited, Surrey, England. p 114-123. Yoklavich, M.M. and G.W. Boehlert. 1987. Daily growth increments in otoliths of juvenile black rockfish, Sebastes melanops: an evaluation of autoradiography as a new method of validation. Fishery Bulletin 85:826-832. Zar, J. H. 1984. Biostatistical Analysis. 2nd Editon. Prentice Hall, Englewood Cliffs, New Jersey. 718 p. 65 Table 1. Number of Albatrossia pectoralis specimens taken for otolith collection by scientific personnel during research cruises off the Aleutian Islands, Alaska, Oregon, and California between October 1993 and October 1997. General capture region, date, latitude (degrees north, 0 N), longitude (degrees west, 0 W), depth (meters, m), number of fish captured, and collection agency (AFSC: Alaska Fisheries Science Center, National Marine Fisheries Service; FITC: Fishery Industrial Technology Center, University of Alaska Fairbanks) are listed. Latitude Longitude Number Region Date (oN) (oW) DeQth (m) of fish Agencl' Aleutian Islands Jul- Aug 1997 51.9 - 53.1 171.7-178.1 401 -465 63 AFSC Alaska Oct 1994 56.0 153.0 455 180 FITC Feb 1995 57.0 151.0 421 124 FITC Apr1995 56.5 152.0 348 44 FITC O"l Apr1996 56.2 153.3 595- 641 158 FITC O"l Oregon Oct - Nov 1993 43.4- 45.4 124.8- 125.1 787- 1250 180 AFSC Oct 1994 44.7-45.5 124.8-125.1 732- 1152 189 AFSC Oct - Nov 1995 42.0-43.0 124.8 - 125.0 478-1165 58 AFSC California Nov 1995 40.5-41.9 124.6-125.1 511 - 1290 109 AFSC Oct 1997 36.4- 37.2 122.2 - 123.2 1151 - 1253 14 AFSC Table 2. Number of Albatrossia pectoralis specimens captured by commercial fishermen off Oregon and California between May 1992 and August 1997, from which otoliths were collected by state agencys. General capture region, date, depth (meters, m), number of fish captured, and donating state agency (ODFW, Oregon Department of Fish and Wildlife; CDFG, California Department of Fish and Game) are listed. Number Region Date De[:Jth (rn) of fish Agenc~ Oregon May 1992 1 ODFW Jun 1993 1 ODFW Jul 1993 1098 1 ODFW Jan 1994 1244- 1281 1 ODFW Mar 1994 1 ODFW Sep 1994 1 ODFW California N of Bodega Canyon Jan 1994 1007 1 CDFG SW of Pt. Sur Aug 1997 915-1018 1 CDFG 67 Table 3. Precision of Reader 1 age estimates for Albatrossia pectoralis. Ageing error is calculated for all samples, for males and females, and for specific estimated age-groups. The number of otoliths aged in each group is noted (n). Otolith weight range (grams, g) and average otolith weight (g) are included for otolith size comparison among groups. Percent agreement is noted for readings within 1, 3, and 5 increments. Average percent error, coefficient of variation, and index of precision are listed. Sex or Otolith Average estimated weight otolith Percent Average Coefficient Index of age-group range weight agreement percent error of variation precision (n) (g) (g) ± 1 ±3 ±5 APE(%) V(%) 0(%) All (357) 0.027 - 0.596 0.146 25.1 52.8 72.7 9.52 12.53 5.60 Male (137) 0.027- 0.436 0.106 24.0 52.4 73.7 10.10 13.22 5.91 0) ()) Female (219) 0.027- 0.596 0.171 25.8 53.2 72.2 9.13 12.06 5.40 13-14 (4) 0.041 - 0.056 0.047 17.5 42.5 57.5 21.72 26.44 11.82 15-19 (38) 0.034- 0.094 0.056 30.3 63.9 80.5 10.87 14.07 6.29 20-24 (81) 0.027- 0.149 0.066 30.9 61.6 80.5 9.80 12.93 5.78 25-29 (75) 0.036 - 0.324 0.098 26.9 52.7 74.7 9.27 12.33 5.51 30-34 (77) 0.034- 0.364 0.168 21.3 46.9 68.8 9.47 12.52 5.60 35-39 (40) 0.062- 0.494 0.250 18.8 47.3 65.8 8.26 11.04 4.94 40-44 (25) 0.142-0.586 0.340 22.4 47.6 68.4 7.86 10.14 4.54 45-49 (14) 0.130-0.596 0.312 16.4 38.6 58.6 8.55 10.97 4.90 50-56 (3) 0.234 - 0.436 0.341 10.0 26.7 40.0 11.83 15.98 7.14 Table 4. Whole Albatrossia pectoralis otoliths used for preliminary 226Ra determination. Sex, general capture region, number of fish and otoliths included in each sample, clean sample weight (grams), 226Ra activity (expressed as disintegrations per minute per gram; dpm/g), qualitative 228Ra content, and sample number are listed. Percent error of 226Ra activity based on TIMS analysis routine(± 1 standard error). Number Number Sample Qualitative Capure of of weight 226Ra (dpm/g) 22sRa Sample Sex region fish otoliths (g) +%error content number Female Oregon 2 2 0.489 0.0312 ± 1.00 NA AP-1 Male Alaska 1 2 0.470 0.0413 ± 1.10 NA AP-2 Male Alaska 1 2 0.494 0.0292 ± 1.10 NA AP-3 NA Alaska 1 2 0.457 0.0422 ± 1.61 NA AP-4 Male Alaska 4 6 0.647 NA negligible AP-5 OJ CD Female Oregon 9 12 0.804 NA negligible AP-6 Table 5. Albatrossia pectoralis otolith core age-groups used for radiometric analyses. Predicted ages for pooled samples were determined by regression analysis of otolith weight and otolith-section age. General capture region, capture date (or range of capture dates), number of fish pooled for each age group, number of otoliths pooled for each age-group, weight of cored otolith age-group (grams, g), weight range of whole individual otoliths pooled for age-group, and sample number are listed for comparison. Number Cored Whole otolith Age- Capture Capture date Number of sample weight range Sample grout! (}'r) region or range of fish otoliths weight (g) (g) number Male 20-25 Oregon 22-28 Oct 94 57 57 0.2965 0.034- 0.077 AP-16 20-25 Oregon 29 Oct -18 Nov 95 37 74 0.3278 0.036 - 0.076 AP-17 21 -25 Oregon 15 Oct - 3 Nov 93 57 68 0.2895 0.041 -0.076 AP-15 -..J 26- 31 Oregon 30 Oct- 19 Nov 95 29 58 0.2820 0.077-0.141 AP-18 0 30-35 Alaska 28 Feb 95 32 60 0.3453 0.124-0.224 AP-14 Female 20-25 Oregon 22-28 Oct 94 62 63 0.3201 0.042 - 0.091 AP-19 20-25 Oregon 29 Oct - 20 Nov 95 39 78 0.3028 0.040 - 0.091 AP-9 25-30 Alaska 31 Oct 94 55 83 0.3768 0.081-0.168 AP-8 25-30 Alaska 2 Apr 96 46 85 0.4020 0.082 - 0.167 AP-10 26-30 Oregon 29 Oct- 18 Nov 95 30 60 0.3012 0.094 - 0.162 AP-13 31 - 35 Alaska 31 Oct 94 53 69 0.3341 0.169-0.280 AP-11 31 - 35 Alaska 2 Apr 96 45 86 0.4463 0.169-0.276 AP-12 Table 6. Radiometric results for pooled Albatrossia pectoralis age-groups. Age-group (years), clean otolith core sample weight (grams), 210Pb and 226Ra activities, 210Pb:226Ra activity ratio, low and high 210Pb:226Ra activity ratios, and sample number are listed. Activities are expressed as disintegrations per minute per gram (dpm/g). 210Pb:22sRa Sample 210pb 22sRa Age-group weight (dpm/g) (dpm/g) Activity Sample (J!r) (g) +%error' +%error' ratio low high number Male 20-25 0.2965 0.033 ± 8.6 0.0621 ± 1.11 0.533 0.482 0.585 AP-16 20-25 0.3278 0.020 ± 10.7 0. 0593 ± 1 . 11 0.341 0.301 0.381 AP-17 21 - 25 0.2895 0.024 ± 10.5 0.0694 ± 1.06 0.340 0.301 0.379 AP-15 26- 31 0.2820 0.026 ± 9.9 0.0585 ± 1.37 0.445 0.396 0.496 AP-18 --.j ~ 30-35 0.3453 0.025 ± 11.8 0.0514 ± 1.07 0.492 0.429 0.556 AP-14 Female 20-25 0.3201 0.028 ± 8.9 0.0638 ± 1.94 0.445 0.398 0.495 AP-19 20-25 0.3028 0.026±11.2 0.0522 ± 1.10 0.498 0.438 0.560 AP-9 25-30 0.3768 0.026 ± 9.8 0.0550 ± 1.05 0.476 0.425 0.528 AP-8 25-30 0.4020 0.032 ± 9.9 0.0566 ± 1.79 0.573 0.507 0.642 AP-10 26-30 0.3012 0.026 ± 9.9 0. 0630 ± 1 .11 0.411 0.366 0.457 AP-13 31 -35 0.3341 0.069 ± 9.0 0.0561 ± 1.17 1.233 1.108 1.360 AP-11 31 -35 0.4463 0.028 + 8.5 0.0463 + 1.34 0.598 0.540 0.658 AP-12 1 Calculation based on standard deviation of 210Pb activity; Wang et al. 1975. 2 Calculation based on TIMS analysis routine (± 1 standard error). Table 7. Von Bertalanffy growth [PAF1 = PAFocl1- e-K(t-ta!)] parameters for Albatrossia pectoralis pre-anal fin length (PAF) at otolith section age. Asymptotic pre-anal fin length 2 (PAF ro) and K were also calculated for to = 0. The coefficient of determination (Adjusted r ), mean square error (MSE), the number of iterations required to meet convergence criteria, and sample size (n) are listed. Error terms are 95% confidence intervals (C. I.}. Confidence intervals could not be calculated for von Bertalanffy parameters when to forced through zero. Forced t = 0 Sexes Sexes Male Female Combined Male Female Combined PAFro 38000* 90 506 106 419 2440 ±C. I. (11678430) (157) (7318) K 0.0000179 0.0149 0.00187 0.00883 0.0229 0.000368 -...j N ±C. I. (0.0055468) (0.0386) (0.02888) to -5.80 5.06 0.868 0 0 0 ±C. I. (42.96) (11.21) (13.924) Adj r 2 0.55 0.62 0.63 0.55 0.62 0.63 MSE 16.64 30.32 27.85 16.71 30.20 27.66 iterations 834 24 255 27 110 470 n 46 93 139 46 93 139 *Male PAF roat maximum constraint of FISHPARM starting parameter matrix. = 8 1 Table 8. Gompertz [PAF1 PAF0 e ( -e-gt)] and linear [PAF = m t + b] growth parameters for Albatrossia pectoralis pre-anal fin length (PAF) at 2 2 otolith section age. The coefficient of determination (adjusted r orr ), mean square error (MSE), the number of iterations required to meet convergence criteria for the Gompertz growth function, and sample size (n) are listed for growth function comparison among sexes. Error terms are 95% confidence invervals (C. I.). Sexes Growth function Parameter Male Female Combined Gompertz PAFO 10.1 2.3 3.8 ±C. I. (9.1) (4.7) (4.6) G 100 3.17 2.86 ±C. I. (39896) (1.61) (0.63) g 0.000 0.052 0.039 ±C.!. (0.115) (0.041) (0.033) Adj r2 0.57 0.62 0.64 MSE 15.89 29.86 27.54 iterations 373 62 139 Linear m 0.680 0.907 0.893 ±C. I. (0.175) (0.146) (0.113) b 3.949 0.399 -0.041 ±C.!. (4.885) (4.762) (3.528) r2 0.58 0.63 0.64 MSE 16.27 30.25 27.65 n 46 93 139 73 Table 9. Von Bertalanffy growth [PAF1 = PAF00 (1- e-K(t-to ))] parameters for Albatrossia pectoralis pre-anal fin length (PAF) at radiometric age. Asymptotic pre-anal fin length (PAF"") 2 and K were also calculated for to = 0. The coefficient of determination (Adjusted r ), mean square error (MSE), the number of iterations required to meet convergence criteria, and sample size (n) are listed. Error terms are 95% confidence intervals (C. I.). Confidence intervals could not be calculated for von Bertalanffy parameters when to forced through zero. Forced t = 0 Sexes Sexes Male Female Combined Male Female Combined PAF"" 23 32110 20930 27 59 42 ±C. I. (15.71) ( 197888580) (34451640) K 2.064 0.000021 0.000030 0.072 0.021 0.035 -.J .j:>. ±C. I. (70827) (0.132308) (0.050548) to 15.23 -10.85 -12.66 0 0 0 ±C. I. (22668.20) (917.05) (248.13) Adj r 2 -1.27 -0.47 0.14 -0.46 -0.03 0.24 MSE 26.54 25.87 19.92 22.80 20.32 18.03 iterations 108 1296 3161 11 18 7 n 5 6 11 5 6 11 •' Head length ; I ';Pre-anal fin length; •Total' length Figure 1. Three length measurements determined for Albatrossia pectoralis: head length (tip of snout to posterior edge of operculum); pre-anal fin length (tip of snout to base of first anal fin ray); and total length (tip of snout to caudal fin). Redrawn from Hart (1973). 75 1 North Pacific Ocean 30° 800 1600 Kilometers Figure 2. Albatrossia pectoralis capture locations within the North Pacific Ocean. Symbols(") represent trawl locations. 76 200 Male and Female 160- TL = 2.15 (PAF) + 25.9 r 2 = 0.93 120 n = 136 ... 80 40 0 0 10 20 30 40 50 60 200 Male E'160 TL = 2.15 (PAF) + 25.9 u 2 ~ r = 0.95 :S 120 n = 33 Olc Q) 80 rn ~ 0 40 1-- 0 ' \ 0 10 20 30 40 50 60 200 Female 160 TL = 2.15 (PAF) + 25.9 r 2 = 0.90 120- n = 102 .. 80 40 0 0 10 20 30 40 50 60 Pre-anal fin length (em) Figure 3. Relationship between pre-anal fin length (PAF) and total length (TL) of male and female Albatrossia pectoralis specimens captured off Kodiak, Alaska. Linear regression equations, coefficient of determination (r), and sample size (n) are listed. 77 200 Male and Female 160- TL=4.02(HL)+21.7 r2 = 0.87 • 120 n = 136 • 80 • • 40 0 0 5 10 15 20 25 30 200 Male TL = 4.05 (HL) + 21.3 E'160- 2 () - r = 0.88 ~ • £ 120- n = 33 OJ c Q) ?~ 80- 0 <1l oF ~ 0 40- 1- 0 ' ' 0 5 10 15 20 25 30 200 Female 160- TL = 3.99 (HL) + 22.3 - r 2 = 0.85 n = 102 • • 120- • • • 80 • • 'II 40 0 0 5 10 15 20 25 30 Head length (em) Figure 4. Relationship between head length (HL) and total length (TL) of male and female Albatrossia pectoralis specimens captured off Kodiak, Alaska. Linear 2 regression equations, coefficient of determination (1 ), and sample size (n) are listed. 78 30 Aleutian Islands Cfl x = 33.9 ± 0.4 n = 63 QJ Male 20 • Female 10 0 30 Alaska 6 x = 26.4 ± 0.4 n = 165 20 Cfl x = 29.3 ± 0.3 6 n = 334 c 10 QJ :::J g o~~~~~~~ I- LL 30 Oregon 6 x = 19.1 ± 0.2 ;f2. n = 196 20 Cflx=21.0±0.4 n = 235 10 California o' s- = 19.4 ± o.6 n = 45 20 ¥ 5( = 24.9 ± 1.0 n = 78 10 0 N CD 0 " 79 Figure 6. Whole Albatrossia pectoralis otolith from an 18 em PAF (pre-anal fin length) male. Otolith viewed on a dark background with reflected light. Scale bar= 1 mm. 80 40 Male and Female OL =0.495 {PAF) + 4.73 30 r 2 = 0.80 • {] =472 20 10 0 0 10 20 30 40 50 40 Male ~ E OL = 0.493 (PAF) + 4.69 E 30 2 ~ r = 0.81 ..c ~ {] = 179 g'2o Q) ..c :!::! 10- 0 ~ 0 0 0 10 20 30 40 50 40 Female OL = 0.490 (PAF) + 4.92 30- r 2 = 0.78 • . {] = 291 20 • 10- 0 0 10 20 30 40 50 Pre-anal fin length (em) Figure 7. Relationship between pre-anal fin length (PAF) and otolith length (OL) of male and female Albatrossia pectoralis. Linear regression equations, coefficient of determination (r), and sample size (n) are listed. 81 0 6 · . Male and Female 0.5 OW= 8.23 x 1o- 5 (PAFj2·29 • · r 2 =0.83 0.4 n=474 0.3 0.2 - 0.1 • 0 10 20 30 40 50 0.6 -,------~ . Male o; o.5 ow= 6.78 x 1 o-5 (PAF)2·35 ~ . 2 0 86 • :E 0.4 r = . • OJ . n = 186 • • -~ 0.3- .c -~ 0.2 .8 0 0.1 • 0~--,---,-~,---,-~ 0 10 20 30 40 50 0.6..------, . Female o.5- ow= 9.82 x 1 o·5 (PAF)2·24 • 0.4.r2 =0.81 • ...... n = 286 •• • • 0.3- • 0.2 - 0.1 04-~-r-~-.-r-~~-.-~~ 0 10 20 30 40 50 Pre-anal fin length (em) Figure 8. Relationship between pre-anal fin length (PAF) and otolith weight (OW) of male and female Albatrossia pectoralis. Allometric growth functions, coefficient of determination (r). and sample size (n) are listed. 82 ventral Figure 9. Three magnified views of a transverse otolith section from a 33-year-old (APE= 7.01 %, V = 9.5%) Albatrossia pectoralis female (36 em pre-anal fin length, PAF). Otolith section viewed with transmitted light. (A) Entire section showing major growth axes, and sulcus acousticus. (B) Close-up view of dorsal and proximal-distal axes, and difficult to interpret increments. Growth increments at the otolith center and along the dorsal-ventral axis are especially difficult to see in this figure. Increments were counted on dorsal side until the 6'h increment was visible on the proximal side. (C) Enlarged view of counting area and growth increments on the proximal side. Growth increments used for age determination are noted~ 61h increment. Scale bar= 1 mm. 83 Percent of Paired Observations Reader1 0 2 4 6 8 10 +32 APE= 9.5 ± 4.5 +28 D = 5.6 ± 2.5 +24 n = 357 +20 +16 en .l!l (1J +12 E :;::> +8 en w +4 ()) 0) <( 0 c -4 ()) u c -8 ,__()) -12 ~ 0 -16 Percent Agreement -20 ±1=25.1% -24 ± 3 = 52.8% -28 ±5=72.7% ±10 = 94.0% -32 Figure 10. Precision of Reader 1 age estimates of Albatrossia pectoralis. Histograms represent the difference (as the percentage of paired age estimates differing by 0, 1, 2, etc.) between readings. The average percent error (APE, %), index of precision (0, %), and standard deviation are listed. Sample size (n) represents the number of otolith sections aged. Otolith sections were read 5 times. The proportions of age estimates which agreed within a certain number of growth increments are listed under Percent Agreement. 84 Percent of Paired Observations Readers 1 vs 2 Readers 1 vs 3 Readers 2 vs 3 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 iO I I I +28- +28 +28 - 0= 7.6 ±6.4 0= 13.7 ±12.1 0 = 12.6 ± 11.5 +24 n =50 +24 n = 44 +24 n = 44 +20: +20 +20 +16 +16 +16 2+12-"' +12 +12 !1l - E +8 +8 +8 :;::; LU"' +4 +4 +4 (l) Ol <( 0 0 0 s; -4 -4 -4 (l) u ():) c -8 -8 -8 (]] (l) ill -12 - %Agreement -12 %Agreement -12 tt:: %Agreement i5 -16: ± 1 = 22.0% -16 ±1=18.2% -16- ± 1 = 11.4% -20 ±3 = 48.0% -20 ± 3 = 34.1% -20 ±3 = 34.1% -24- ±5 = 70.0% -24 ±5 = 40.9% -24 ± 5 = 43.2% ±1 0 = 82.0% ±1 0 = 63.6% ±1 0 = 70.5% -28 -28 -28 Figure i i. Precision of age estimates between three readers of Albatrossia pectoralis. Histograms represent the difference (as the percentage of paired age estimates differing by 0, i, 2, etc.) between readers. The index of precision (0, %) and standard deviation are listed for each comparison. Sample size (n) represents the number of otolith sections aged. The proportions of age estimates which agreed within a certain number of growth increments are listed under Percent(%) Agreement. 70.------. 60 50 N ij:; 40 "~po 0:: 20 . 10- o~--~~~-.~~~~-.~~ 16 20 24 28 32 36 40 44 48 52 Age estimated by Reader 1 70.------~------, 60 50- ""ij:; 40 "~po 0:: 20 _: 10- 04-~-r,-~-r~~-r.-~-r.-ro~ 16 20 24 28 32 36 40 44 48 52 Age estimated by Reader 1 70.------, 60 "" 50 . ij:; 40 "m 3o- o:: 20 10 a+-~~~~-.~~~.-~~~ '16 20 24 28 32 36 40 44 48 52 Age estimated by Reader 2 Figure. 12. Age bias plots for each of the pairwise reader comparisons. The age estimates of reader Y are plotted as the mean age and 95% confidence interval corresponding to each of the age categories of reader X. The 1:1 equivalence line is drawn for reference. 86 1.0 -rr======::::J------, --R =0.2 0 ·--R =0.1 0 --- R =0.0 0.8 0 0 Male 0 :;:::; x Female ~ 0.6- / / / 0.2- / 0.0~-~--~-~-~~~~~~~~-~-~~~-~ 0 5 10 15 20 25 30 35 40 45 50 Radiometric age and predicted age (years) Figure 13. Expected 210Pb: 226Ra activity ratio ingrowth curves and observed activity ratios for male and female Albatrossia pectoralis. The x-axis represents radiometric age for the expected ingrowth curves, and predicted age for the observed activity ratios of the pooled otolith age groups. Ingrowth curves represent possible initial uptake ratios (R 0 ) of 210 Pb: 226Ra. Observed activity ratios are plotted against mean age of pooled otolith age-groups. Horizontal bars represent the age range of pooled otoliths (predicted from otolith weight by the regression model; shaded rectangles), and 95% confidence intervals of the youngest and oldest predicted ages in the age-group (horizontal capped-lines). Vertical bars represent the analytical uncertainty of 210 Pb and 226 Ra measurements. 87 SOT.======~------~ 0 Male 45- X Female 40_: y = 0.68x + 5.08 r 2 = 0.272 (j) 35-: n = 11 ~ ~------~ tU (jJ - 2)30-: (jJ OJ tU 25- 0 ·c ~ (jJ - E 20-: 0 Regression '5 tU 15 - 0::: - 10- Line of agreement 0~-~~~~~~~~~~~~~~~~ Figure 14. Comparison of mean predicted age and radiometric age for male and female Albatrossia pectoralis pooled otolith age-groups. Regression and agreement lines are drawn for comparison. The regression equation, coefficient of determination (r), and sample size (n) are noted. Horizontal bars represent the age range of pooled otoliths (predicted from otolith weight by the regression model; shaded rectangles), and 95% confidence intervals of the youngest and oldest predicted ages in the age-group (horizontal capped-lines). Vertical bars represent low and high radiometric age estimates, based on analytical uncertainty of 210Pb and 226Ra measurements. 88 70 Male 1-166 60- n =46 1-146 50- -126 40- 0 0 0 0 1-106 0 0 30- 0 0 0 86 Cb ocg o 0 20- ctP~§ c8 -66 ~ ©o §o E 0 0 10- ~ ~ -46 E .c 0 ~ -Ol 0 , I , , I , 26 .c c ' ' ' Ql Ol 0 10 20 30 40 50 60 -c c Ql <.:= 70 rn rn c Female -166 X -0 rn 60- n = 93 1- Ql' -146 '- xx 0.. 50 X -126 40- X ~XX~ 106 x . ~»>'xxx 30 Q;r 86 20 -66 t \~~X 10-: 1-46 0 I I 26 ' ' ' ' 0 10 20 30 40 50 60 Estimated age (years) Figure 15. Estimated age at length for male and female Albatrossia pectoralis. Total length calculated from partial length analysis. 89 50,------, Male f-126 n=5 40- -106 T 30- fJ 'T-~-~ -86 20- l=~=lT '1--f1--~·---4 ' -66 1 E'u 10- -46 ~ o~~~.• ,~~.~ ,.~.~~,.~.~.~ ,~. .. ~~~·~,~.~~ .• ,~~T26 _c ~ 0 5 10 15 20 25 30 35 40 Ol c 50.------. ~ ~ Female -126 Jll 0 cp 17=6 1- ~ 40- 0.. T 106 30 86 20- 66 '10 46 o~~~~~.T,~.~.~~~~~~~~~~.~.,,~.~~26 0 5 10 15 20 25 30 35 40 Radiometric age (years) Figure 16. Radiometric age and mean pre-anal fin length for male and female Albatrossia pectoralis pooled otolith age-groups. Horizontal bars represent low and high radiometric age estimates, based on analytical uncertainty of 210Pb and 226 Ra measurements. Vertical bars represent standard deviation (shaded rectangles), and range (vertical capped-lines) of PAF in the pooled otolith age-group. Total length calculated from partial length analysis. 90 70 Ku/ikova Pautov This study PAFco 52 45 90±157 166 X 60-j K 0.1606 0.1558 O.D149±0.0386 . I 1.99 2.18 5.06±11.21 0 146 .. n 5 15 93 x>< ~so E X u 126 ~ )( ~ E ~ Kulikova (1957) ..... X u 40l ~ X ~ c · (sexes combined) ...... X >