Otolith Sections Research Articles

Age and Growth of Atlantic Croakers in the Northern Gulf of Mexico, Based on Otolith Sections

Otoliths from 1,291 Atlantic croakers Micropogonias undulatus, with total lengths from 113 mm to 417 mm, from the northern Gulf of Mexico were examined to determine age and growth. Marginal increment analysis was used to determine that otolith marks formed annually. Ages ranged from 0 to 8 years. No significant difference was found for length at age between males and females. The von Bertalanffy equation was Lt = 419.2[1 - e−0.273(t+1.405)], where Lt = total length (mm) and t = age (years). The length-weight relationship (r = 0.99) was W = 5.302 × 10−6TL3.134 where W = weight (g) and TL = total length (mm).

Age determination of eels, Anguilla anguilla (L): comparison of field data with otolith ring patterns

Otoliths of eels recaptured up to 5 years after tagging were used for comparative work on the determination of annual ring patterns. It was possible to locate false annuli caused by the tagging procedure and subsequently to define annual rings in otoliths within the known period between first tagging and final catch. This determination gave an estimate of the size of the annual zones. Growth depression caused by tagging could be shown in cross sections of otoliths. Well defined annulus patterns in micrographs of otoliths from tagged eels were compared with otoliths from untagged eels. This comparison allowed a dimensional calibration of the ageing method and the recognition of misleading additional rings. Mean annual length increments of 47.88 mm and Lx, of 123.3 mm were determined.

Use of Otoliths to Determine Age and Growth of Largemouth Bass in Florida

Abstract The annual formation of otolith annuli was validated through age 5 for Florida largemouth bass Micropterus salmoides floridanus. Sectioned otoliths (sagittae) gave more reliable ages than whole otoliths. Beginning at age 2, at least one annulus was obscure in some whole-otolith mounts, a problem that worsened with fish age. By age 5, over 20% of the whole otoliths gave under-estimates of true age; otoliths producing these errors came from fish with slower than average growth rates. Sectioned otoliths gave poorer regressions (lower coefficients of determination) of otolith radius on body length than intact structures because the sectioning plane varied slightly among otoliths. Nevertheless, back calculations of fish size and growth from sectioned and correctly aged whole otoliths were equally accurate. Otolith sectioning is the procedure of choice for age-and-growth analysis of Florida largemouth bass. Whole otoliths, however, require much less time for analysis than sectioned ones and may be used...

A low-speed alternative method for cutting otolith sections

A low-speed alternative method for cutting otolith sections

Rhythmic structural and chemical patterns in otoliths of the Antarctic fish Notothenia larseni: Their application to age determination

Sagittal otoliths from Notothenia larseni contain microincremental growth rings which are distinctly visible in otolith sections using Scanning Electron Microscopy. These microincrements are similar to those deposited daily in the otoliths of fishes from temperate and tropical waters. Microincrements were easily enumerated and fish length was related to increment number by a logarithmic curve. Otolith microstructure analysis appears to provide a technique to accurately determine age and growth rates in these fish. Sr/Ca ratios in otolith aragonite were analyzed along a radius from the outside edge to the core of an otolith section using an electron microprobe. The strontium/calcium (Sr/Ca) ratios varied with a cyclic periodicity apparently related to seasonal water temperature cycles and the number of cycles agreed closely with age estimated from “daily” microincrement counts. Sr/ca cycles can potentially be used to determine age, validate growth rates determined by other methods, and establish thermal conditions experienced during the life of a fish. Microstructural and chemical analyses of otoliths demonstrate great potential in helping to answer many questions about the growth processes and ecology of Antarctic fishes.

Age and Growth of Largemouth Bass in a Thermally Altered Reservoir, as Determined from Otoliths

Abstract Comparative growth rates of largemouth bass (Micropterus salmoides) from heated and ambient areas of Coffeen Lake, Illinois, were estimated by back calculation of lengths at annuli using transverse sections of otoliths and by recovery of marked fish after one growing season. Calculated lengths at otolith annuli were judged to be representative of the population growth, indicating that this technique was a reliable approach to obtaining growth information on largemouth bass from thermally affected environments. Growth of the Coffeen Lake population was more rapid than most other midwest populations. Fish recaptured in heated areas generally exhibited greater annual growth increments than those recaptured in ambient areas. Young largemouth bass (ages 1-4) from heated areas had significantly greater (P < 0.05) mean lengths than those from ambient areas according to back-calculated estimates. This was attributed to a longer growing season and earlier hatching time in thermally affected areas.

Population Parameters of a Relatively Unexploited Stock of Snowy Grouper in the Lower Florida Keys

Abstract Age, growth, mortality, and reproduction of a relatively unexploited stock of snowy grouper Epinephelus niveatus from the lower Florida Keys, were studied during April 1978-July 1981. Biological statistics were derived from 309 snowy grouper. Ages, determined by otolith sectioning, ranged from 0 to XXVII. Back-calculated mean total lengths (TL) ranged from 209 mm at the end of year 1 to 909 mm at the end of year 15. The von Bertalanffy growth equation for snowy grouper was Lt = 1,320{1 - exp[-0.087(t + 1.013)]}, where L = total length (mm), and t = age (years). Annual mortality, determined by catch-curve analysis, was 16%. Full recruitment into the fishery occurred at 575–600 mm TL and at age VIII. The snowy grouper exhibited protogynous hermaphroditism. Most females (81%) were sexually mature by age IV to V. Males did not appear until age VI, but they comprised 40% of all fish of ages VIII or older. These biological findings preliminarily suggest that snowy grouper stocks in the Florida Keys can...

A method for preparing sections of large numbers of otoliths embedded in black polyester resin

A process is described in which otoliths are carefully positioned in rows in specially prepared moulds which are then filled with liquid black polyester resin. The resin hardens to form solid rectangular blocks with the otoliths embedded in them. The blocks are removed from the moulds and machined with a high-speed diamond saw. Thin slices are cut from the blocks precisely along the lines of the centres of the rows of otoliths. The slices are mounted and fixed onstandard glass microscope slides. The otolith sections are then ready for reading. Up to 90 otoliths at a time may be processed in a single mould and the technique of positioning them is described. The setting up and machining of the blocks of polyester is also described as are the machine, moulds, and materials used. Comments are made on the extended range of possibilities for viewing the otolith sections produced by the method.

Age Determination of Manitoban Walleyes Using Otoliths, Dorsal Spines, and Scales

Otolith sections were used to determine ages of walleyes (Stizostedion vitreum) collected from four Manitoban lakes. To verify the presence of annuli on otolith sections, ages determined from otoliths were compared to ages derived from dorsal spine sections and scales; mean body lengths back-calculated from 252 otolith sections were compared to mean observed lengths; and otolith sections from known-age walleyes were aged. Otolith sections not only can provide accurate age estimates and back-calculated length estimates for young walleye populations but also they are easier to age, and consequently are more accurate for determining ages of older walleyes than are scales and dorsal spines.

Verification of the Formation of Annuli in Otoliths of Largemouth Bass

Annuli in transverse thin sections of otoliths from largemouth bass Micropterus salmoides were verified by four methods. First, the number of daily rings between successive annuli was similar to the potential number of growing days in each of the first 3 years of life. Second, all of the annuli were formed between the last of April and the first part of July. Third, the lengths of age-I-VI largemouth bass back-calculated from otoliths were very similar to those determined from a mark-recapture study. Fourth, the number of otolith annuli agreed with the known ages (II+ and V+) of largemouth bass in samples from a hatchery and a lake.

Confirmation of longevity in Sebastes diploproa (Pisces: Scorpaenidae) from 210Pb/226Ra measurements in otoliths

Fish ages are often estimated by assuming an annual frequency of the band-like, growth-zones recorded in the largest of their otoliths, the sagittae. The total number of growth-zones are normally determined either by counting external growth-zones (whole otolith technique) or by examining otolith cross-sections (otolith section technique). The two techniques do not always yield the same age, however, particularly in older specimens of certain fishes. To resolve this problem, otoliths of the splitnose rockfish Sebastes diploproa were examined morphologically and were assayed for their natural radionuclide concentrations. Four age groups of otoliths were identified based on growth-zone counting; in the first three, whole otolith and otolith section age estimates agreed, while in the fourth, the otolith section age substantially exceeded the whole otolith age. Radiometric analysis demonstrated that all otoliths were deficient in 210Pb activity relative to 226Ra activity with the deficiency decreasing with increasing number of growth-zones. The magnitude of the 210Pb/226Ra radioactive disequilibrium in each otolith group, when compared to the number of growth-zones and the otolith weight histories derived with the two techniques, identifies the growth-zones revealed by otolith sections as annual features. Thus when otolith section age exceeds whole otolith age (usually occurring after 20 to 25 yr of age for this species), the otolith section technique is the correct method of age determination. Estimates of longevity in the genus Sebastes near 80 yr are therefore confirmed.

Age Validation of Redfish,Sebastes marinus(L.), from the Gulf of Maine-Georges Bank Region

Age determinations of redfish up to age 7 from the Gulf 'of Maine-Georges Bank region were validated by noting the seasonal formation of hyaline and opaque edges on otolith sections and by comparing estimates of mean length at age with observed modes of length frequencies specific to the 1971 year-class. Evidence was found for the formation in the otolith of one hyaline and one opaque edge annually. Hyaline edges predominate from November to May and opaque edges from June to October. Deposition of hyaline material, as indicated by the presence of a very narrow edge, generally begins in August and the formation of the opaque edge begins in April. Average length at age values based on otolith readings were similar to observed modes of length frequencies known to represent the 1971 year-class on the basis of the seasonal progression of modal length groups from 1971 to 1978.

New Information on the Longevity of Pacific Ocean Perch (Sebastes alutus)

A comparison of ages determined from surfaces of otoliths and from sections of otoliths showed that ages were similar up to a section age of 22–24 yr. The growth pattern observed on thin sections of otoliths and from broken and burned otoliths from the region of the nucleus was interpreted to indicate that Pacific ocean perch probably live much longer than previously thought. Because the criteria used to identify annuli from otoliths sections appeared valid for younger fish, there was no justification to reject the application of these criteria for estimating ages of older fish and thus no reason to reject the possibility that Pacific ocean perch might live to be older than 70 yr. Ages determined from sections of otoliths from other rockfish species found off the west coast of Canada such as Sebastes fiavidus and Sebastes brevispinis have ranged from 30 to 60 yr indicating that many species of rockfish may live longer than previously thought. Key words: age determination, otolith, maximum age, age determination errors, Pacific ocean perch, otolith sections

Differences in the Age of Pacific Hake (Merluccius productus) Using Whole Otoliths and Sections of Otoliths

Ages determined for older Pacific hake from sections through the nucleus of otoliths were older than the ages determined from the otolith surface for the two populations studied. Growth of all parts of the otolith was not identical throughout the life of the fish. The change in the pattern of otolith growth occurred about the age at which the growth in length of the fish was reduced. Despite the disproportionate growth in length and height of the otolith, the thickness of the otolith, especially in the ventral interior portion, continued to increase with age. Section ages appear to be more reliable for older fish because of this allometric change in otolith growth with increasing fish age. It is suggested that the examination of sections of otoliths should become a routine approach in any attempt to age fish using otoliths. Key words: age determination, otolith, otolith section, otolith growth, aging errors, Pacific hake, Strait of Georgia

Age and Growth of Jack Mackerel, Trachurus declivis (Jenyns), from South-eastern Australian Waters

Jack mackerel data were collected between October 1973 and February 1976 from south-eastern Australian waters. Otoliths were read using reflected light on (1) the surface of the whole otolith and (2) the broken and burnt transverse sections of the same otolith. Growth rings were read to 13 years in the first method and to 16 years in the second. Otolith radius (R, nucleus to posterior margin) measured along the concave surface was related to fish length (L) in a curvilinear form: R = 2.39L0.6635. Otolith intermediate radii (rn) plotted against fish length for ages 1 to 10 years indicated a regular deposition of growth rings. Growth according to the von Bertalanffy equation was slow (L∞ = 46.3, K = 0.23). No significant difference between the mean lengths was apparent between sexes at most ages. The geometric mean regressions of length on weight indicated differences between fish in spawning and non-spawning condition.

A Method for Cutting Sections of Otoliths of Cod and Other Fish

A Method for Cutting Sections of Otoliths of Cod and Other Fish