Use Of Otoliths Research Articles

Estimating Age and Growth of Largemouth Bass in Southwestern Reservoirs by Using Otoliths and Scales

Abstract Age and growth data are frequently used to monitor and manage important North American sport fishes such as Largemouth Bass Micropterus salmoides. Continental and regional growth standards have been developed for this species to assess fish growth over time and across space. However, Largemouth Bass age and growth data are infrequently collected in Arizona and the reliability of age estimates derived from typical structures (e.g., scales, otoliths) in the Southwest is uncertain. Our objectives were to 1) compare precision and bias of age estimates from scales with those from otoliths and 2) estimate Largemouth Bass growth in several southwestern warmwater reservoirs by using otoliths. We collected Largemouth Bass from three Arizona reservoirs—Alamo, Peña Blanca, and Roosevelt—by boat electrofishing in spring 2021. We removed scales and sagittal otoliths from fish and then prepared and independently aged them three times. We compared differences in precision and bias between scales and otoliths using reader agreement percentages, confidence ratings, average coefficients of variation, and age-bias plots. We used age estimates from Largemouth Bass otoliths to calculate mean lengths-at-age at capture and relative growth indices based on published growth standards in each reservoir. Largemouth Bass scale age estimates were less precise, overestimated ages of younger fish, and underestimated age of older fish compared with those of otoliths. Growth was lower in Peña Blanca Lake than in the other two reservoirs according to mean length-at-age estimates, and relative growth indices suggested that Largemouth Bass growth in all three reservoirs was above average at younger ages, but less so at older ages. The results from this study add to a growing body of literature supporting the use of otoliths for estimating age and growth of Largemouth Bass.

Validation of the Use of Otoliths to Estimate Age and Growth of Larval Lake Whitefish, Coregonus clupeaformis

Understanding drivers of recruitment variation in fish populations requires research conducted on early life stages. Examination of fish otoliths provides useful information for estimating hatching dates, growth, and survival rates of larvae and for investigating the relationship between early life stage phenology and variation in environmental factors such as climate and food availability. In the Laurentian (i.e., North American) Great Lakes, significant reductions in the number of young (ages 1–4 years) lake whitefish (Coregonus clupeaformis) recruiting into the population and commercial fishery have raised questions about factors affecting growth and survival of the larval life stage. Here, we investigate the utility of using otoliths to estimate the age and growth of larval lake whitefish. We raised offspring of wild-caught parents from Lake Simcoe (Ontario, Canada) in a hatchery environment and analyzed otoliths of these known age fish for 75 days posthatch. We further examined otoliths of wild-sampled larvae and age 0 lake whitefish from Lake Huron. We found a strong linear relationship between known age and number of postcheck increments on the otolith and between growth of the otolith and fish length. Increments formed at nearly 1 (0.9) per day beginning at day 20 after hatch. Check and subsequent increment formation was associated with disappearance of the yolk sac. Wild fish had more prominent checkmarks and grew slower than hatchery fish. Thus, otolith analysis represents a promising tool to examine dynamics of early life stages of lake whitefish, although further research is required on the effects of environmental conditions on otolith microstructure.

Otolith Morphometric and Shape Distinction of Three Redfin Species under the Genus Decapterus (Teleostei: Carangidae) from Sulu Sea, Philippines

Otoliths are paired calcified structures in the inner ear of teleosts that function in hearing and balance. In this study, the use of otolith morphometrics and shape analysis were explored to delineate the redfin species under the genus Decapterus from the Sulu Sea, Philippines, namely, Decapterus kurroides, D. smithvanizi, and D. tabl. Results showed that the mean otolith shapes are unique within species (p < 0.001). The otolith size-related (OW—otolith weight, OL—otolith length, OH—otolith height, OA—otolith area, and OP—otolith perimeter) and shape-related (RE—rectangularity, SQ—squareness, EL—ellipticity, RO—roundness, AR—aspect ratio, FF—form factor, CO—compactness, and CI—circularity) morphometric indices also showed significant variations (p < 0.001) among the three species. Distinct regions differentiating D. kurroides from the other two species were seen along the dorsal margin of the otoliths, which was supported by its significantly higher values for OH (size-related index) and RO (shape-related index). In addition, the morphometric indices showed significant variations (p < 0.001), except for RE. Furthermore, it was revealed that the size-related indices were able to separate D. kurroides from the other two species, which turned out to be indifferent. The results provided relevant data on the use of otoliths as an additional confirmatory tool in species delineation of the identified redfin species, and, therefore, offer opportunities of applying the same method in delineation and, eventually, identification of species from other genera, especially those that closely resemble each other.

Age and growth of grey triggerfish Balistes capriscus from trans-Atlantic populations.

Anthropogenic factors that negatively impact reef fishes can include changes in life-history patterns of fisheries-targeted species. Understanding these impacts on growth and population age structure is essential in the management of exploited populations of fishes. This is the first study to directly compare age and growth for a major fisheries species between east and west populations of a transatlantic reef fish. The main goal of this study was to document age and growth in grey triggerfish Balistes capriscus from coastal waters of Ghana in the Gulf of Guinea (GOG) and compare those with the previous growth studies from that region and with the western Atlantic population. A secondary objective of this study was to evaluate the use of otoliths to age triggerfish and to provide a preliminary comparison with spine-derived age estimates. The results obtained from this study provided an updated understanding of the growth and age structure of the eastern B. capriscus population in GOG. The authors documented that shifts in population attributes occurred for B. capriscus after its major decline in abundance. The differences in physical and biotic characteristics of the East and West Atlantic regions and the differences in collection methods of samples make direct comparisons of growth parameters difficult. Nonetheless, overall differences in maximum sizes and ages were apparent; the western Atlantic population had a larger maximum size and older maximum age. The authors also documented that sagittal otoliths can be used to provide age estimates for triggerfish species, and otoliths as an ageing structure had better between-reader precision compared to dorsal spines.

Fishing for “lucky stones”: Symbolic uses of otoliths in Brazilian shell sites

Otoliths are concretions of aragonite located in fish neurocrania, also popularly known as “lucky stones”. These elements are commonly found in Brazilian shell mounds and middens, and have long been regarded as a by-product of food processing and consumption. Zooarchaeologists commonly use them to identify species, estimate age, quantify fish, and to discuss capture methods and seasonality of occupation, among other aspects of fish and human populations. My research at Jabuticabeira II, a cemetery site with large quantities of otoliths closely associated with burials, explores alternative uses of otoliths by past coastal populations that inhabited the southern Brazilian coast. I reviewed ethnographic and historical accounts of the use of otoliths to check distinct uses of these fish elements. I analyzed 9258 otoliths and 76,990 fish bones from Jabuticabeira II to identify patterns of fragmentation, thermal alteration, element representation and distribution across contexts. The results indicate that otoliths were deliberately placed in burials, pointing to the symbolic value of otoliths. This research reinforces the need to consider the non-economic uses of fish by pre-historic populations.

Fish otoliths: uses of their structural, shape and chemical properties in ichthyology

Event Abstract Back to Event Fish otoliths: uses of their structural, shape and chemical properties in ichthyology Alberto T. Correia1, 2* 1 Centro Interdisciplinar de Investigação Marinha e Ambiental, Portugal 2 Faculdade de Ciências da Saúde da Universidade Fernando Pessoa, Portugal Otoliths are inner ear aragonitic concretions used as hearing and balance organs by teleost fish. These hard structures have unique properties allowing them to have several applications in fish science. Otoliths are classically used to estimate the age of fish by counting daily and/or annual growth increments, particularly important for fisheries management purposes (e.g. determination of age at first maturity). Moreover, the tracking of some microstructural checks under visual microscope observation allow us to identify some key ecological life history fish events (e.g. settlement age). At present, the use of otolith morphology (e.g. landmarks and shape contour) is also contributing to assess the population structure of commercially important fish stocks. Recently, the use of high precision analytical methodologies permitted that the microchemistry (e.g. elemental and isotopic signatures) of otoliths had a remarkable growing in the last few years. At present, otoliths could complement, or even replace, other natural tags, such as the common genetic tools (e.g. mt-DNA and usat-DNA), in the study of the population structure, movement patterns and habitat connectivity in fish. Several published examples of the current applications and methodological pre-requisites of the use of fish otoliths will be shortly explored during this presentation. Moreover, future challenges of the otolith science will be also pinpointed. Acknowledgements This research was partially supported by the Strategic Funding UID/Multi/ 04423/2019 through national funds provided by Foundation for Science and Technology (FCT) and European Regional Development Fund (ERDF) in the framework of the programme PT2020. Keywords: fish, Natural tags, otoliths, Applications & Properties and Structure, Life-cycle Conference: XVI European Congress of Ichthyology, Lausanne, Switzerland, 2 Sep - 6 Sep, 2019. Presentation Type: Key-note Presentation Topic: OTOLITHS AS A TOOL TO STUDY FISH LIFE CYCLES Citation: Correia AT (2019). Fish otoliths: uses of their structural, shape and chemical properties in ichthyology. Front. Mar. Sci. Conference Abstract: XVI European Congress of Ichthyology. doi: 10.3389/conf.fmars.2019.07.00001 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 24 Jun 2019; Published Online: 14 Aug 2019. * Correspondence: Prof. Alberto T Correia, Centro Interdisciplinar de Investigação Marinha e Ambiental, Matosinhos, Portugal, atcorreia.ciimar@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Alberto T Correia Google Alberto T Correia Google Scholar Alberto T Correia PubMed Alberto T Correia Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Precision of Calcified Structures Used for Estimating Age of Chain Pickerel

AbstractWith the exception of Northern Pike Esox lucius, there is a paucity of information on the precision of age estimates based on calcified structures for esocid species, especially Chain Pickerel E. niger. We estimated ages for 42 Chain Pickerel from Stevens Creek Reservoir on the Savannah River, South Carolina–Georgia. Ages were estimated using sectioned pelvic, pectoral, dorsal, and anal fin rays, scales, cleithra (sectioned and whole), and otoliths to assess precision between repeated readings (four readers). Precision was evaluated by calculating agreement among readers, CV, and mean absolute difference (MAD) in estimates between reader pairs. We tested for differences in precision of estimates among structures using linear mixed models with CV or MAD as the response. Finally, we used age bias plots to evaluate whether there were structure or reader‐related systematic biases in estimates. Coefficient of variation and MAD were significantly related to structure type (CV: P = 0.006, MAD: P = 0.001) and mean estimated age (CV: P < 0.001, MAD: P = 0.025). Precision was poor for all structures and poorest for age‐0 fish; however, all analyses indicated that otoliths provided the most precise estimates. We observed agreement in estimates among all readers for 40% of the otoliths examined and consensus agreement for 74% of the estimates. Coefficient of variation for otoliths declined from 67% for fish with a mean estimated age of 0 years to 5% for age‐4 fish. Conversely, MAD for otoliths increased from 0.34 years for fish with a mean estimated age of 0 to 0.46 years for age‐4 fish. Estimates from all structures, except pectoral rays, were negatively biased compared with estimates from otoliths. We recommend the use of otoliths for age estimation of Chain Pickerel, but managers and researchers should be cognizant of and evaluate the potential effects of variability in age estimates among readers on their analyses.

Otolith chemistry does not just reflect environmental conditions: A meta‐analytic evaluation

AbstractFish otoliths are widely used to answer biological and ecological questions related to movements and habitat use based on their chemical composition. Two fundamental assumptions underlie otoliths as environmental tracers and proxies for reconstructing exposure histories: (i) otolith chemistry reflects water chemistry, and (ii) ambient environmental conditions affect otolith element incorporation. Here, we test these assumptions for Sr and Ba through meta‐analyses. Our first meta‐analysis confirmed a correlation between concentrations of Sr:Ca and Ba:Ca in otoliths and the surrounding water, both elements displaying positive otolith–water correlations. The second meta‐analysis examined the relative influences of salinity and temperature on otolith Sr and Ba partition coefficients (an index of otolith element regulation). Our environmental effects meta‐analysis confirmed that otolith Sr and Ba are affected by temperature and salinity; however, study‐level covariates (e.g., water chemical concentrations and species ecological niche) influenced otolith element incorporation, and this varied by element. These findings confirm that even though otolith chemistry and elemental incorporation are differentially affected by environmental conditions, other factors play a decisive role. While we focused on studies that directly linked water and otolith chemistry, systematic reviews are key to further demonstrate the link between otolith chemistry and extrinsic and intrinsic factors. Ultimately, disentangling the relative effects of multiple factors on otolith chemistry and a detailed understanding of biomineralization is critical to the continued use of otoliths as natural tags for tracing fish movements and habitat use.

Blue marlin (Makaira nigricans) longevity estimates confirmed with bomb radiocarbon dating

The longevity of blue marlin (Makaira nigricans) remains unresolved. The use of fin spines and sagittal otoliths for age reading has led to unconfirmed longevity estimates near 20–30 years. Age validation has been elusive because large individuals are uncommonly caught, and a technique that can be applied to structures that provide estimates of age was absent. The use of otolith chemical signatures has been limited by sagittal otoliths that are very small — whole otolith mass of adult blue marlin rarely exceeds 10 mg for the largest fish. Recent advances in the detection limits of radiocarbon (14C) with accelerator mass spectrometry — coupled with recently acquired knowledge of marine bomb 14C signals spanning the tropical Pacific Ocean — have led to an opportunity to age blue marlin from small amounts of otolith material. In this study, otoliths from a recently collected 1245 lb (565 kg) female blue marlin at a measured 146-inch (371 cm) lower jaw fork length were analyzed for 14C. Estimated longevity was either 12–21 or 32–44 years on the basis of bomb 14C dating. Using multiple lines of evidence, it was determined that the young age scenario was most likely, with evidence for an age close to 20 years using a series of deductions in the bomb 14C dating method.

Chemical archives in fishes beyond otoliths: A review on the use of other body parts as chronological recorders of microchemical constituents for expanding interpretations of environmental, ecological, and life‐history changes

AbstractMicrochemical analyses of fish otoliths have revolutionized fisheries science. Molecules deposited within otoliths may originate from ambient water and diet, with molecular concentrations being subject to subsequent physiological alteration after exposure. Analyses of otolith microstructure and incorporation of inorganic elements have led to major advances in stock assessment and fisheries ecology. However, the use of otoliths for microchemical analyses has drawbacks. Specifically, otolith removal from live specimens requires specimen sacrifice, which may be forbidden in the case of protected species. In addition, otoliths rarely contain sufficient concentrations of organic matter to allow reconstruction of food‐web relationships via multiple stable isotopes, and otolith microstructure can be difficult to interpret in some species. Here, we review alternatives to otoliths that can provide microchemical analytes for life‐history studies in fishes. Our focus is to describe advantages and disadvantages to the use of each alternative structure, with particular attention paid to trace‐element analysis for inorganic matrices and stable‐isotope analysis for organic ones. In general, the chronological analysis of elemental and isotopic values within each structure depends on the inert nature (or lack of molecular turnover) of the tissue. Structures with high turnover rates or those that are metabolically active will not effectively record elemental or isotopic compositions over time. Here, we provide an assessment of the use of bony endoskeleton, fin spines, fin rays, scales, and eye lenses as alternatives or complements to fish otolith analysis.

Can analysis of Platichthys flesus otoliths provide relevant data on historical metal pollution in estuaries? Experimental and in situ approaches

Despite recent efforts to manage them more efficiently, estuaries are natural sinks for a wide range of metal contaminants, many of which accumulate at potentially toxic concentrations for fish populations, posing a threat to recruitment and stocks. While analysis of metal concentrations in soft tissue and water samples calls for continuous and long-term sampling operations, the use of otoliths to study metal pollution may be one way of providing a historical record of pollutant exposure. In this study, we examine the potential use of otoliths as natural tracers of metal contamination. A “cocktail” of different metals (Cd, Pb and Ni) was used to test bio-accumulation in otoliths and tissue (liver, kidney, muscle and gills) extracted from juvenile flounder (Platichthys flesus). Assessment took place under controlled conditions over a three month period, with water exposure concentrations increasing every 3weeks. The concentrations used were natural (T1), X5 (T2), X10 (T3), and null (T4). Chemical analyses were carried out using an inductively coupled plasma optical emission spectrometer ICP-OES and atomic absorption spectrometer AAS for water and tissue, while otolith microchemistry analyses were performed using a femtosecond laser ablation-high resolution inductively coupled plasma mass spectrometer (fsLA-ICP-MS-HR). Significant differences between control and exposed individuals, as well as an increase in metal concentrations according to exposure level, were observed in all tissues except in muscle tissue. Significant increases in Pb were also detected in contaminated fish otoliths compared with control specimens, with the highest concentrations occurring in T3. Cartographies of Pb distribution in otoliths of both control and contaminated fish only showed high concentrations of Pb at the edge of contaminated fish otoliths, indicating an accumulation of metal during the experiment. Although the relationships between exposure level and Pb concentration in otoliths were complex, the concentrations were correlated with those in the water. Analysis of flounder specimens collected from 2007 to 2014 in the Gironde estuary (SW France) showed interannual variability in Pb concentrations, with higher values for fish otoliths from 2007 to 2010 than those from 2012 to 2014. This trend indicated a decrease in Pb in the Gironde estuary over the last decade, which is consistent with the results of other surveys on bivalves. Our study demonstrates that it is possible to use otolith microchemistry as a tool in assessing and retracing long-term metal pollution in estuarine systems.

Otoliths in archaeology: Methods, applications and future prospects

Otoliths are small structures found in the inner ear of teleost fish that act as organs of equilibrium and as direction and sound detectors. They possess unique characteristics that set them apart from other skeletal structures, notably a continuous growth structure deposited on a daily basis. While otolith analyses are widely employed in modern fisheries studies, they have slowly been increasing within archaeological and palaeoenvironmental research. This paper overviews the development and future prospects of otolith studies in archaeology. The main methods of analysis are outlined and major advances and research in each area detailed. In spite of some limitations, the benefits and unique information that otolith analyses can provide ensure that otoliths should be an important part of archaeological research. Continuing development of methods and technologies within this area will serve to further increase the importance and use of otoliths, while raising the profile of this unique resource.

Validation of otolith ages for walleye (Sander vitreus) in the Winnebago System

Although accurate age data are essential when estimating somatic growth and mortality rates required to effectively manage exploited walleye (Sander vitreus) populations, aging structures have not been validated for age ranges present in most walleye populations. Otoliths and dorsal spines were collected from 302 walleye considered known age in the Winnebago System, Wisconsin, USA: 142 that were assigned ages via progression of discrete length modes following an individual strong year class (ages 0–3), and 160 (ages 4–10, 12–13, 16, 18) that were initially tagged at lengths small enough to accurately assign age ±1 year (<380mm) and later recaptured and assigned an age (assigned age at tagging plus number of years at liberty). Paired aging structures were also collected from over 2000 additional walleye sampled during spawning assessments, tournament monitoring, and other surveys to better understand the relationship between spine and otolith age estimates and to compare catch curve residuals from structure and sex-specific catch curves to standard walleye recruitment indices. We found otoliths were accurate for walleye ages 0–10, while dorsal spines yielded relatively accurate age estimates for walleye ages 1–5, but underestimated age of walleye age-6 and older. Age distributions within catch curves constructed from otolith age estimates correlated well with measured year class strength, while age distributions from dorsal spine age estimates correlated poorly. Our results from fish considered known age validate the accuracy of otolith age estimates for walleye up to age-10, with corroborating evidence from catch curves and accurate recruitment indices strongly suggesting that otoliths are valid for all ages of Winnebago System walleye. We recommend the use of otoliths to accurately estimate walleye age, growth, and mortality, and to provide accurate age data for other population analyses.

In search of the dead zone: Use of otoliths for tracking fish exposure to hypoxia

Otolith chemistry is often useful for tracking provenance of fishes, as well as examining migration histories. Whereas elements such as strontium and barium correlate well with salinity and temperature, experiments that examine manganese uptake as a function of these parameters have found no such correlation. Instead, dissolved manganese is available as a redox product, and as such, is indicative of low-oxygen conditions. Here we present evidence for that mechanism in a range of habitats from marine to freshwater, across species, and also present ancillary proxies that support the mechanism as well. For example, iodine is redox-sensitive and varies inversely with Mn; and sulfur stable isotope ratios provide evidence of anoxic sulfate reduction in some circumstances. Further, S may be incorporated trophically whereas other elements appear to be taken up directly from water. This research suggests a potential means to identify individual fish exposure to hypoxia, over entire lifetimes. With further testing and understanding, in the future fish may be able to be used as “mobile monitors” of hypoxic conditions.

Impacts of Aging Error on Walleye Management in the Winnebago System

AbstractThe age data used to manage Walleye Sander vitreus fisheries are not always accurate, as otoliths typically provide more accurate age estimates for larger, older Walleyes than dorsal spines. We assessed the impacts that the aging error associated with the use of dorsal spines has on the estimated age distribution, growth and mortality rates, and yield per recruit for Walleyes in the Winnebago system, Wisconsin. Age distributions derived from otolith age estimates more accurately portrayed variable recruitment than those derived from dorsal spine age estimates. The mean estimates of instantaneous total annual mortality developed from sex‐specific catch curves were greater when dorsal spine age estimates were used (0.515 for males, 0.493 for females) than when otolith age estimates were (0.349 for males, 0.396 for females), with most of the differences being observed in natural mortality estimates. The von Bertalanffy growth models were not significantly different, but the yield‐per‐recruit models (which rely heavily on von Bertalanffy model parameters) incorporating spine age data produced average yield estimates 50–70% lower than the models developed from otolith ages. The yield‐per‐recruit models derived from spine‐determined ages also resulted in lower recommendations as to the age and size of fish for maximum yield at all exploitation levels than the models developed from otolith age data. The mean dorsal spine and otolith age estimates were similar for male Walleyes &lt;457 mm and female Walleyes &lt;508 mm, but for larger fish otoliths yielded significantly older ages than spines. Given the economic and social impacts of the Winnebago system Walleye fishery, we recommend exclusive use of otoliths to obtain the most accurate estimates of fish age, growth, mortality, and yield. In populations in which the sacrifice of large quantities of fish is not acceptable, we recommend using spines to estimate the ages of smaller fish (males &lt;457 mm, females &lt;508 mm) and otoliths to estimate the ages of fish larger than these critical lengths.Received December 26, 2012; accepted June 10, 2013

Otolith Age Validation and Growth Estimation from Oxytetracycline‐Marked and Recaptured American Shad

AbstractThis study validated a whole‐otolith aging method using known‐age American shad Alosa sapidissima from the Delaware River system. Although scale ages are commonly used in autecological and assessment studies of American shad, scale ages from the same fish could not be validated. New data reported here used known‐aged otoliths and scales available from shad marked by oxytetracycline as larvae in a hatchery and recaptured as adults on or near their spawning ground. A subset of whole otoliths were examined and annuli—defined as a pair of translucent and opaque bands—were counted using males and females ranging in age from 3 to 9 years. The reading and interpretation of annuli by the more experienced reader were accurate with respect to the known age, whether measured as the percent agreement (PA = 80%) or Chang's coefficient of variation (CV = 3.11). The use of otoliths provided more accurate results than scales obtained from the same fish (PA = 46%; CV = 7.84). A second reader, who had no previous experience with this species, had lower performance scores but also performed better with otoliths; this demonstrated the need for training and testing when using the whole‐otolith aging method. Growth modeling using ages of known‐age juveniles and adults confirmed dimorphic growth. Females grew larger than males (von Bertalanffy L∞ = 552 and 495‐mm FL, respectively). The maximum age observed for females was only slightly older than males (9 versus 8 years). The superiority of the otolith‐based age method makes it difficult to compare our results with older, scale‐based demographic studies, but it represents an improved method for generating ages for future stock assessments.

Contrasting population characteristics of yellow bass (Morone mississippiensis) in two southern Illinois reservoirs

Summary Two southern Illinois reservoirs were investigated with contrasting size structures of yellow bass (Morone mississippiensis) to compare growth, mortality and recruitment patterns. Yellow bass were collected from Crab Orchard and Little Grassy lakes during April–May 2009 using AC electrofishing. Total length and weight were recorded and sagittal otoliths sectioned and aged by two readers. Increments between otolith annuli were measured and the Weisberg linear growth model was used to assess age and environmental (growth year) effects on individual growth for fish from the two lakes. Von Bertalanffy growth models indicated faster growth and a greater maximum total length for yellow bass in Little Grassy Lake. However, growth of fish in Little Grassy Lake nearly ceased after age 4. The Weisberg model indicated differences in individual growth rate between the two lakes that were consistent across years (age effects were significant, but growth year effects and the age-growth year interaction were not). Inter-lake differences in fish growth were present up to age 3. Recruitment was relatively stable in Crab Orchard, with year classes up to age 7 observed. Recruitment was more erratic in Little Grassy, with age 5 being the dominant year class and fish up to age 11 present. Differences in growth and recruitment patterns for yellow bass in the two lakes may be attributed to substantial inter-lake differences in turbidity, morphoedaphic index, or yellow bass density. Maximum age of yellow bass (age 11) was higher than previously reported for this species, likely due to the use of otoliths to age fish rather than scales. This study provides baseline information on age and growth, mortality, recruitment, and size structure of yellow bass that can be compared to data in future studies to elucidate factors influencing population dynamics of this species.

Lake Erie Yellow Perch Age Estimation Based on Three Structures: Precision, Processing Times, and Management Implications

AbstractYellow perch Perca flavescens support economically important recreational and commercial fisheries in Lake Erie and are intensively managed. Age estimation represents an integral component in the management of Lake Erie yellow perch stocks, as age‐structured population models are used to set safe harvest levels on an annual basis. We compared the precision associated with yellow perch (N = 251) age estimates from scales, sagittal otoliths, and anal spine sections and evaluated the time required to process and estimate age from each structure. Three readers of varying experience estimated ages. The precision (mean coefficient of variation) of estimates among readers was 1% for sagittal otoliths, 5–6% for anal spines, and 11–13% for scales. Agreement rates among readers were 94–95% for otoliths, 71–76% for anal spines, and 45–50% for scales. Systematic age estimation differences were evident among scale and anal spine readers; less‐experienced readers tended to underestimate ages of yellow perch older than age 4 relative to estimates made by an experienced reader. Mean scale age tended to underestimate ages of age‐6 and older fish relative to otolith ages estimated by an experienced reader. Total annual mortality estimates based on scale ages were 20% higher than those based on otolith ages; mortality estimates based on anal spine ages were 4% higher than those based on otolith ages. Otoliths required more removal and preparation time than scales and anal spines, but age estimation time was substantially lower for otoliths than for the other two structures. We suggest the use of otoliths or anal spines for age estimation in yellow perch (regardless of length) from Lake Erie and other systems where precise age estimates are necessary, because age estimation errors resulting from the use of scales could generate incorrect management decisions.

Direct Validation of Annual Growth Increments on Sectioned Otoliths from Adult Arctic Grayling and a Comparison of Otolith and Scale Ages

AbstractAccurate ages are essential for the responsible management of fish populations, and validation of ages ensures that accurate age estimates are available to managers. Scales have typically been used to estimate ages of Arctic grayling Thymallus arcticus in Alaska; however, the recapture of marked fish after several years at large has cast doubt on the accuracy of scale ages for this species. To validate age determinations from otoliths, we used oxytetracycline (OTC) to mark 102 Arctic grayling from the Eldorado River, Seward Peninsula, Alaska, during 1994 and 1995. Fish were tagged, fin‐clipped, weighed, and injected with 25 mg of OTC/kg of body weight. Over the succeeding 4 years, 16 OTC‐marked Arctic grayling were recaptured. Fluorescent marks were visible in thin‐sectioned otoliths from 15 of the 16 recaptured fish, and annuli that were visible beyond the mark accurately recorded the passage of years between mark and recapture in all otoliths with OTC marks. Ages assigned from scales underestimated the otolith‐assigned age by as much as 20 years. We assembled a larger data set of scale–otolith pairs (n = 74) by combining data from sampling mortalities collected in nearby rivers during 1988–1995 with data from this study. We used the Fisheries Analysis Simulation Tool (FAST 2.1) to estimate growth parameters, and we used an age bias plot and a simple population model to illustrate the mismanagement of Arctic grayling fisheries that could occur if scale ages are relied upon to describe stock structure. We recommend the use of otoliths as the standard of age determination in Arctic grayling populations until a nonlethal method (e.g., fin rays) can be validated for age determination in this species.

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 Lt = 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.