An assessment of otoliths,dorsal spines and scales to age the long‐finned gurnard,Lepidotrigla argus,Ogilby, 1910 (Family: Triglidae)

Sagittal otoliths, dorsal spines and scales were critically assessed as structures to potentially determine the age of the long‐finned gurnard, Lepidotrigla argus. Counts were made of opaque growth increments and a readability score was assigned to each structure. Comparisons of growth increment counts were made between structures and between readings. All three structures showed some degree of readability and quantifiable growth increments, but this varied within fishes and between structures. Initial results showed that whole otoliths were more suitable to determine age estimates than dorsal spines and scales. Scales were considered unsuitable due to between reading ageing bias, variation in age estimates between structures, low precision and poor readability for this species. Dorsal spines showed evidence of loss of growth increments due to hollowing of the vascular core, which resulted in underestimation of older individuals in comparison to whole otoliths. Further analysis showed that growth increment counts from whole otoliths were lower for older individuals in comparison to sectioned otoliths. It is suggested that this is because of decreased clarity of growth increments towards the outer margin of whole otoliths in older individuals; this problem was not present with sectioned otoliths. It was concluded that sectioned otoliths were a more suitable structure from which to estimate age of L. argus than were whole otoliths, dorsal spines and/or scales.     

Age determination,growth and mortality of Gerres subfasciatus Cuvier, 1830 in southeast Australia

Commercial beach‐seine (30–50 mm cod‐end mesh) catches of Gerres subfasciatus in Lake Macquarie southeast Australia were sampled monthly between December 2000 and April 2002 to investigate species age, growth and mortality characteristics using sectioned sagittal otoliths. Inclusion of fishery‐independent length data of young‐of‐the year collected from littoral seagrass beds with fine meshed beach seines augmented growth analyses. Fifty otoliths each month (total 448 female and 402 male) were examined with sections displaying alternating opaque and translucent zonation. Formation of otolith opaque zones occurred annually between August and December as determined by monthly marginal increment analyses. Spawning occurred between October and February, and a universal birth date of 1 December was assigned that allowed counts of opaque zones to be converted to age estimates in years and months (decimal ages). The von Bertalanffy growth function identified that both genders grew fast for their initial 2 years, but thereafter slowed. Females grew faster, had a greater mean fork length‐at‐age, estimated L_∞ and an observed greater maximum fork length in samples compared to males. Nevertheless, observed longevity was 10⁺ years for both genders. Commercial catches of both genders were dominated by the 2⁺ and 3⁺ year age classes. Catch curve analyses identified the instantaneous rate of total annual mortality to be ~0.8 and an exploitation rate of <0.5 for both genders. The data form a basis for developing assessment and management strategies of G. subfasciatus fisheries.     

Otolith annulus validation and variables influencing false annuli formation in dorsal spines of saugeye

Marginal increment analysis is a common technique for validating formation of a single annual growth ring on an ageing structure. False annuli can form on ageing structures when environmental variables affect growth of a fish, potentially resulting in age estimation bias. Therefore, validating ageing structures is essential to ensure that accurate and precise age estimates are collected when assessing fish population dynamics. Saugeye (Sander vitreus, [Mitchill, 1818]) and S. Canadensis, [Griffith and Smith, 1834]) are highly valued sport fish that are stocked across the Midwest United States. Using marginal increment analysis, we confirmed that a single annulus was formed yearly in otoliths of juvenile saugeye, however two annuli formed in dorsal spines in a single year. Timing of the first annulus formation in both otoliths and dorsal spines was completed after a slow growth period during winter (otoliths forming in April; dorsal spines forming in March). The second annulus (false annulus) that formed during August in dorsal spines did not form in otoliths. To understand what environmental factors may influence the false annulus to form, we collected monthly water temperatures and percent empty stomachs of juvenile saugeye. The highest water temperatures of the year occur during July and August, which resulted in saugeye seeking thermal refuge and affecting feeding habits. Mean monthly temperature and percent empty stomachs were positively correlated, so during times of high temperatures foraging rates declined, suggesting the formation of false annulus on dorsal spines of juvenile saugeye. This study demonstrates how thermal stress affected accuracy of non‐lethal aging structures and further emphasizes the need for age validation studies prior to using non‐lethal ageing structures to estimate age for a particular species from different aquatic systems.     

Age and growth of the common carp, Cyprinus carpio, in the River Murray, Australia: validation, consistency of age interpretation, and growth models

The present study validates age estimates from a suite of calcified structures (scales, opercular bones and otoliths), assesses the consistency of age interpretations and evaluates growth models in common carp from the lower Murray River, Australia. Marginal increment analysis was used to validate annulus counts, with attention to the 'edge interpretation problem'. The formation of annuli occurred annually after pooling annulus groups, and in carp 4 and 5 years old. The regular alternation of opaque and translucent zones in opercular bones and whole otoliths of younger and older carp was also suggestive of annual periodicity. From systematic comparisons, the use of both opercular bones and whole otoliths in routine age determinations is recommended. Six growth models, including the von Bertalanffy growth function (VBGF) and five polynomial curves were tested to describe growth in length. A log-log quadratic function, by virtue of its precision, and the VBGF, with wider applicability and more biological realism, were chosen.     

Validation of annual periodicity in otoliths of red snapper, <Emphasis Type="Italic">Lutjanus campechanus</Emphasis>

The periodicity of otolith growth increments (opaque and translucent zones) from adult red snapper (Lutjanus campechanus) was examined through a mark and recapture study (2005–2010), and laboratory holding of hatchery reared red snapper over a 2 year period (2002–2004). Wild red snapper (n = 295) were caught hook-and-line, marked with anchor tags, injected with oxytetracycline dihydrate (OTC), and released in the Gulf of Mexico 15–40 km south of Dauphin Island, Alabama. Marked fish were recaptured up to 2.8 years after release (n = 35) and sagittal otoliths were dissected, sectioned and examined under white and blue-violet light. The number of opaque growth zones past the OTC mark was compared to time at liberty for each fish and supported an annual periodicity of growth increment formation. Also, most (87%) of the hatchery reared fish showed two opaque zones that supported an annual increment formation rate. However, an unusual timing of opaque zone formation was shown for mark-recaptured fish. Based on known timing of OTC marking, otoliths from mark-recapture fish showed opaque zone formation from late summer (August) to early winter (December). This fall formation of opaque zones is in contrast to previous studies and its timing may relate to the end of spawning for this species.     

The use of otolith microstructure to estimate age in adult Atlantic cod Gadus morhua

Transverse sections of otoliths from Atlantic cod Gadus morhua from the Baltic Sea revealed narrow growth increments. The widths of these increments corresponded to daily increments from fish with known otolith growth rates and were therefore assumed to be daily increments. They exhibited a distinct pattern with increasing distance from the primary primordium. A series of zones with clearly distinguishable increments, first with increasing then with decreasing widths in a dome‐shaped pattern, were separated by zones where no regular increment structure was visible. Increment width seemed to be tightly coupled to the annual cycle in environmental temperature at a depth of 30–60 m, where G. morhua predominantly reside. Between 135 and 200 increments occurred within the different zones, with a non‐significant trend towards lower increment numbers and widths with distance from the primary primordium of the otolith. Increment formation apparently ceased at temperatures < 5–6° C, but growth during the cold months corresponded closely with estimated growth rates. The increment patterns seemed to reflect annual cycles in environmental temperature, and the count of the increment cycles may thus be a promising tool for the determination of the true age of Baltic G. morhua.     

The growth of the common two-banded seabream, Diplodus vulgaris (Teleostei, Sparidae), in Canarian waters, estimated by reading otoliths and by back-calculation

The yearly nature of increment formation in the otoliths of 1–9‐year‐old seabream, Diplodus vulgaris (E. Geoffrey Saint‐Hilaire 1817), from the Canary Islands was validated. The marginal increment method showed that the opaque rings were formed in summer, and the translucent rings in winter. The Brody Proportional Hypothesis and the power length–radius relationship used to back‐calculate the growth trajectories of D. vulgaris showed that this growth model could provide reasonable growth estimates in this species. Growth back‐calculation and growth estimates obtained by direct otolith readings were similar. Data on age and size used to estimate the parameters of the von Bertalanffy growth model for D. vulagris from the Canary Islands showed that males and females had similar growth rates.     

Otolith formation,microstructure and daily increment validation in juvenile perch Perca fluviatilis

The otoliths of laboratory‐reared larval and juvenile perch Perca fluviatilis of known age were analysed to determine the age of otolith formation and validate the formation of daily increments. There was a linear relationship between number of increments and age in days post‐hatching, although by 82 days post‐hatching daily increment counts underestimated actual age by an average of 5 days. Otolith dimensions in relation to standard length indicated allometric growth of otoliths until completion of yolk absorption, and isometric growth thereafter, up to 82 days post‐hatching.     

Preliminary estimates of the age and growth of immature smooth oreo Pseudocyttus maculatus Gilchrist 1906 (Oreosomatidae) in the Falkland Islands region of the South Atlantic

Sectioned otoliths were used to estimate the age of 29 specimens of the smooth oreo (Pseudocyttus maculatus Gilchrist 1906) from the Falkland Islands region of the South Atlantic. This represents the first ageing study of this species in this region of the world. All specimens were immature (sub-adults), the largest having a maximum total length of 347 mm. Growth increments were observed in sectioned otoliths and assumed to be annual in periodicity. The maximum age estimate of individuals in this study was 20 years and the form of somatic growth was similar to previous research on this species from Australian waters. The otolith microstructure consisted of an inner, mostly opaque zone with wide increments followed by an outer, mostly translucent zone with narrower increments. It is suggested that these zones correspond to the two growth phases in the life history of this species, namely the pelagic juvenile phase (opaque zone) and the demersal sub-adult/adult phase (translucent zone). Received: 27 May 1997 / Accepted: 31 October 1997     

Age and growth analysis of the mosshead sculpin Clinocottus globiceps Girard 1857 (Pisces: Cottidae) from Helby Island, British Columbia

The age and growth of the cottid fish Clinocottus globiceps Girard from tidepools at Helby Island, British Columbia, Canada were investigated with the aid of whole saccular otoliths (sagittae); ages were validated by marginal increment analysis. Four hundred and twenty five specimens were examined from 214 females and 211 males. Marginal increment analysis on specimens with one to three opaque zones suggested an annual ring deposition in sagittae during the late autumn and spring months.
The C. globiceps population was composed of individuals from less than 1 year to 5 years of age for fish measuring between 5–120 mm standard length. Growth was faster for younger than for older age groups. Lengths-at-age data were fitted to the Gompertz growth model, and estimates of the model parameters L₀, G and g were 26.7 mm 1.58 and 0.30 for pooled cohorts, respectively. The highest levels of growth occurred during late spring and early summer, when water temperatures were at maximum and food was most abundant. The lowest levels of growth occurred during the autumn and winter months.     

Age validation and growth of three commercially important hemiramphids in south-eastern Australia

The method of using sectioned otoliths to estimate age in three species of garfishes (family Hemiramphidae) was validated by: (1) staining fishes with the vital stain alizarin complexone (ALC) and periodically examining their otolith growth, and (2) marginal increment analyses. Staining fishes with ALC indicated that opaque zones were formed during winter and spring, but did not become visible on the otolith edge until late spring and summer. Hyporhamphus australis were found to be similar to the hemiramphids of the Atlantic in having fast growth rates and a maximum observed age of 4+ years old. Hyporhamphus regularis ardelio and Arrhamphus sclerolepis krefftii were found to be more similar to the southern sea garfish, Hyporhamphus melanochir , in being moderately long-lived, with maximum observed ages of 7+ years old for both species. Females grew faster and attained greater fork lengths than males for each species. Sectioned otoliths showed large variation in the appearance of opaque zones between the three species studied, with those from the wide-ranging, oceanic H. australis appearing inconsistent and diffuse when compared to the estuarine H. r. ardelio and A. s . krefftii . This variation was also apparent from fishes kept in aquaria, suggesting that the appearance of opaque zones in otoliths of these species is largely influenced by physiology, rather than by environmental conditions.     

Age validation,and comparison of otolith,vertebra and opercular bone for estimating age of <Emphasis Type="BoldItalic">Schizothorax o’connori</Emphasis> in the Yarlung Tsangpo River,Tibet

A collection of 514 Schizothorax o’connori was made between August 2008 and August 2009 from Yarlung Tsangpo River to assess the suitability of three bony structures for age estimation. The annulus characteristics of otolith, vertebra and opercular bone were described. Location of the first annulus was validated by daily growth increment (DGI) analysis in the otoliths. Annual periodicity was verified by marginal increment ratio (MIR) analysis in otoliths and edge analysis in vertebrae and opercular bones. Annuli formed, once a year, between March and May for all three bony structures. Otoliths, vertebrae and opercular bones were examined to determine which structure produced the most precise and accurate age estimates in S. o’connori. Vertebrae and otoliths matched closely for the first 21 years of life, while opercular bones appeared to underestimate age. For older fish, the counts diverged and otoliths consistently providing higher age estimates. Sectioned otoliths proved to be the most precise and accurate structure for age estimation. The oldest observed schizothoracine fish was 50, more than twice the longevity previously accepted in S. o’connori.     

Use of otoliths to determine age and growth of a tropical flatfish Cyclopsetta querna (Paralichthyidae) from the southeast coast of the Gulf of California, Mexico

Age and growth of the tropical flatfish Cyclopsetta querna were determined from the sagittal otoliths. From yearly marginal growth increment trends, it was concluded that the opaque and hyaline zones were formed annually. The oldest individual was a 43.2-cm (5-year-old) female. No significant differences in length-at-age were found between sexes. The von Bertalanffy growth equation for the entire population was L_t = 60.71 (1 − e ^{(−0.245(t−0.408))}). The life span of these species is short, about 5 years. The otoliths proved a reliable structure to determine age of this species.     

Age validation and variation in growth,mortality and population structure of Liza argentea and Myxus elongatus (Mugilidae) in two temperate Australian estuaries

This study investigated variation in the rates of growth and mortality, and age and fork‐length (L_F) compositions of two exploited species of Mugilidae, Liza argentea and Myxus elongatus, in two south‐east Australian estuaries (Lake Macquarie and St Georges Basin). An ageing protocol was developed by counting opaque growth zones on sectioned otoliths which was validated by periodically examining the otoliths of captive‐reared young‐of‐the‐year fishes, and marginal increment analysis of wild fishes. The maximum recorded age was 17 years for L. argentea and 12 years for M. elongatus, which is greater than generally observed in other species of mugilids. Growth models of each species significantly differed between sexes and, except for male L. argentea, between estuaries. Fishes from Lake Macquarie generally had a greater mean L_F at age than those from St Georges Basin and females of both species generally attained a greater maximum L_F and age than males. Gillnet catches of L. argentea were of similar L_F and age compositions in both estuaries, whereas the age composition of catches of M. elongatus in Lake Macquarie contained a greater proportion of younger fish. Estimates of total, natural and fishing mortality were greater for M. elongatus than L. argentea across both estuaries, and estimates of total mortality were greatest for both species in Lake Macquarie. The data indicate that neither species has been overfished in these estuaries.     

Trace elements in the otoliths and dorsal spines of albacore tuna (Thunnus alalunga, Bonnaterre, 1788): An assessment of the effectiveness of cleaning procedures at removing postmortem contamination

Trace element analysis or “elemental fingerprinting” is widely used in stock structure analyses. Postmortem contamination of bony structures can confound the results of microconstituent studies or introduce an additional source of noise to the data, thus reducing the ability of the technique to detect real variation in trace element concentrations. Despite the potential for postmortem contamination during sample preparation, the effectiveness of the procedures used to remove potential contaminants from sectioned otoliths and other calcareous structures prior to laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS) has not previously been addressed. Otoliths and dorsal spine sections of albacore tuna (Thunnus alalunga) collected from the North East Atlantic Ocean and the Mediterranean Sea were deliberately contaminated prior to analysis of trace element composition using LA ICP-MS. The effectiveness of three cleaning treatments (rinsing in ultrapure water, 30% hydrogen peroxide and ultrapure 5% nitric acid) at removing this postmortem contamination were compared. Magnesium and strontium were relatively robust to postmortem effects when exposed to contamination at concentrations of 50 ppm and 200 ppm respectively. Soaking in a solution containing Mn, Cs and Ba (50 ppm) caused a marked increase in the detected concentration of each element in both structures. Translucent bands in both structures were more susceptible to contamination. Rinsing in ultrapure water or hydrogen peroxide was not effective at removing Mn, Cs and Ba contamination from either calcareous structure. Washing the otoliths and spines in nitric acid successfully removed postmortem contaminants.The removal of otoliths from tuna damages the appearance of the fish and has an adverse effect on market value. However spines are easily removed, do not affect the appearance or value of the fish and are the most commonly used structure for age determination. A weak but significant correlation was observed between Ba in opaque zones in otoliths and dorsal spines. All other spine to otolith correlations were not significant. The results do not provide support for the use of spines as an alternative to otoliths in trace elemental analyses.     

Age, growth, mortality and population characteristics of the pearl perch, Glaucosoma buergeri Richardson 1845, from deeper continental shelf waters off the Pilbara coast of north-western Australia

Pearl perch, Glaucosoma buergeri Richardson 1845, from deeper waters (> 100 m depth) on the continental shelf of north-western Australia were aged by examining transverse sections of their sagittal otoliths. Ages were assigned based on counts of alternating opaque and translucent zones (annuli). Otolith length and breadth (width) increased linearly with fish length, whereas otolith weight increased linearly with fish age. The continuous growth of the otoliths provides some evidence that the opaque and translucent zones used to estimate age in this study are formed on a regular basis. Parameters of the length–weight relationship were estimated, along with parameters of the von Bertalanffy growth function. The generalised von Bertalanffy growth function (total length-at-age, both sexes combined) for G. buergeri was L _t=512.7 (1 – e^{–0.139( t  + 0.89)}). There was no significant differential growth between the sexes in observed length-at-age. The oldest individual found was a male G. buergeri estimated to be 26 years of age. The annual instantaneous rate of natural mortality ( M ) was estimated to be 0.14. The slow growth, long life and low natural mortality rate indicate that G. buergeri is vulnerable to overfishing and that harvest strategies for this species should be conservative, given its low production potential.     

Validation of annulus formation in otoliths of largemouth bass Micropterus salmoides outside their native range

The periodicity of growth zone formation was validated for largemouth bass Micropterus salmoides using edge analysis (EA) and mark recapture of chemically‐tagged wild fish (MRCT) to test the hypothesis that one opaque and hyaline zone was deposited annually in sagittal otoliths sampled from temperate South African M. salmoides populations. For 35 fish recaptured in the MRCT experiment, the relationship between the number of growth zones posterior to the chemical mark and the time at liberty (0.04–1.38 years) did not differ significantly from a 1 : 1 relationship (t‐test, t = 0.76, d.f. = 2,33, P = 0.45). This result was supported by EA, where periodic logistic regression and a binomial model linked with a von Mises distribution for circular data demonstrated that the frequency of otoliths with opaque margins followed a unimodal distribution (maximum October–January). Both the timing of growth zone deposition (spring) and the annual rate were consistent with results from validation studies conducted globally in localities ranging from 45°N to 33°S, and indicate that the growth zone deposition rate is annual throughout the native and introduced range of this species.     

Age and growth of the dusky grouper Epinephelus marginatus (Lowe 1834) in an exploited population of the western Mediterranean Sea

The age and growth of the dusky grouper, Epinephelus marginatus , in the Balearic Islands (western Mediterranean) were studied by otolith analysis from a sample of 358 specimens ranging in total length ( L _T) from 6·6 to 105·6 cm. The specimens came from commercial artisanal and recreational spear fisheries between 1999 and 2003. Otoliths grew asymmetrically throughout the range of L _T studied, showing a clear pattern of alternating translucent and opaque bands. Marginal increment analysis of specimens up to 8 years-old indicated that a single opaque band was formed each year during spring and summer. Whole otoliths allowed ageing specimens up to 10 years old, but above that age whole otoliths yielded lower age estimates than sectioned otoliths. The maximum estimated age was 61 years, which significantly extends the estimated life span of the species from a maximum of 36 years in a previous study. The von Bertalanffy growth parameters were estimated as L _∞= 95·5 cm L _T, K = 0·087 and T _O=−1·12. The study revealed differences in mean L _T at age and age structure between the shallow- and deep-water samples which may be attributed to different fishing pressure and environmental conditions.     

Age and growth of longnose trevally (Carangoides chrysophrys) in the Arabian Sea

The ages and growth of longnose trevally (Carangoides chrysophrys), caught in the northwest Arabian Sea between April 2005 and September 2006, were investigated. Age and growth of 336 fish specimens were determined using sectioned sagittae otoliths. Annual opaque growth rings were formed between December and March, with the majority being laid down in February and March, coinciding with the spawning period and high water temperatures. Marginal zone or edge analysis was used to validate the annual deposition of the opaque zone in the otoliths. This species showed large variations in length‐at‐age, suggesting large growth variations among individuals of the same cohort. The estimated von Bertalanffy growth model differed significantly between the sexes, with males having larger mean lengths at age and reaching a larger asymptotic size. The von Bertalanffy growth models were TL (cm) = 73.34[1‐exp (?0.25 (t + 1.21))] and TL(cm) = 73.26[1‐exp (?0.24 (t + 1.20))] for males and females, respectively.     

Age estimation,growth and maturity of the Argentine hake (Merluccius hubbsi Marini, 1933) along the northernmost limit of its distribution in the south-western Atlantic

Age, growth and length-at-maturity of the Argentine hake (Merluccius hubbsi) were studied in the northernmost limit of the species distribution in the south-western Atlantic. A total of 351 otoliths and information from 1610 specimens sampled from the industrial double-rig trawl landings between May 2013 and April 2014 were used. Age and growth were estimated by counting and measuring increments in sectioned sagittae otoliths, and length at maturity was estimated based on macroscopic gonadal analysis. For both sexes, hepatosomatic index and condition index increased mainly during spring, reaching a maximum at the end of summer before the subsequent spawning season began. Gonadosomatic index was highest in April, believed to correspond with peak spawning. The annual periodicity of alternate opaque and translucent zones was validated by marginal increment analysis. Growth curves were fitted to back-calculated size at age by fitting the three-parameters von Bertalanffy growth function. The maximum age was 5 years in fish of either sex. Females attained larger sizes than males. The parameters of the von Bertalanffy growth equations were: L∞?=?533?mm, k?=?0.231 year^?1 and t₀?=??0.935 year for females; L∞?=?394?mm, k?=?0.405 year^?1 and t₀?=??0.463 year for males. The mean length and age at first maturity was 273?mm at 1.9 years for males and 274?mm at 2.0 years for females.