Daily Rings Research Articles

Validation of otolith daily increment formation and early growth analysis of Japanese flounder (Paralichthys olivaceus)

The Japanese flounder is a vital economic species among East Asian released and cultured fish. Here, we sought to validate daily increment formation and analyze the early morphological development of sagittal otoliths and lapillus in Japanese flounder larvae and juveniles over 50 days. Our analysis focused on the otolith shapes, the number of daily rings present, and their length and width measurements. The results revealed that sagittal otoliths and lapillus formed before the fertilized eggs hatched. During the larval and juvenile stages, sagittae evolved gradually, transforming from nearly round to oval structures, eventually adopting arrow- or pear-shaped forms. Similarly, lapillus transformed from nearly round to mussel-shaped structures. The first daily ring became evident on the 5th-day post-hatching, demonstrating a daily periodicity during the larval phase. We observed a direct relationship between incubation days (D) and the number of daily otolith increments (n), expressed as D = n + 5. This deposition trend exhibited a daily periodicity for both sagittae and lapillus. We also noted exponential correlations between the length (Ls, μm) and width (Ws, μm) of the sagittae and the total length (TL, mm). Contrastingly, the lapillus measurements demonstrated linear correlations. Furthermore, a linear relationship emerged between the sagittae and lapillus lengths: Ll = 0.3028Ls + 28.534 (R2 = 0.9366). Additionally, we found a similar linear relationship between the sagittae and lapillus widths: Wl = 0.3791Ws + 21.508 (R2 = 0.9426). The formation pattern of daily increments in lapillus was notably more distinct than that in sagittae, making it highly suitable for age identification and group recognition. This study not only contributes to the field of fish ecology but also provides a foundational understanding for future research. It can assist in reconstructing early life histories and inferences about the spawning periods and grounds of stocked Japanese flounder.

Validation of otolith daily ring deposition and hatch date estimations in larval and juvenile Japanese flounder Paralichthys olivaceus

The early life history traits of Japanese flounder Paralichthys olivaceus, a commercially important species, have been well studied; however, daily ring formation in otoliths (lapilli and sagittae) of this species has not been investigated in detail. We examined the daily periodicity of ring deposition in otoliths using hatchery-reared Japanese flounder larvae and juveniles. In both lapilli and sagittae, a check corresponding to the radius at hatching (ca. 6 µm) was discernible throughout the pelagic larval and settled juvenile periods. The otolith rings were faint in the preflexion larval period and distinct in the flexion larval and later periods. Regression analyses for the number of rings by age in days showed that ring deposition occurred daily in lapilli but not in sagittae. Double marking of juveniles with alizarin complexone confirmed the daily ring periodicity in lapilli. However, the first faint ring was observed in the innermost areas in lapilli at 3–16 d post-hatching, and the faint rings were often unrecognisable, even under a scanning electron microscope, which interfered with daily age estimation. To estimate the number of days corresponding to the obscure zone with unrecognisable rings in lapilli, we developed the estimation method using logarithmic functions derived from the relationship between the radius (restricted to <20 µm) of lapilli and the ring counts for individual data. The error for the estimated days was − 0.05 ± 2.13 (n = 26, mean ± SD), indicating that this method is useful for hatch date estimation. Thus, the present study provides a novel method for analysis of otolith daily increments with unclear narrow rings in the innermost part of the otoliths.

Extracting daily isotopic records on fish otolith (Trachurus japonicus) by combining micro-milling and micro-scale isotopic analysis(MICAL-CF-IRMS).

The recent progress in micro-scale isotopic analytical techniques for otoliths has enabled the reconstruction of the experienced water temperature history of fish in every few days resolution using the stable oxygen isotope ratio (δ18 O) of otoliths. We aimed to improve those techniques and extract the daily δ18 O records of otoliths formed during the juvenile period. Growth rings were formed daily in fish otoliths. We precisely distinguished the daily rings in otoliths of Japanese jack mackerel Trachurus japonicus, and milled them along daily growth rings using a high-spatial resolution micromilling system (Geomill326). Then, we determined the stable carbon and oxygen (δ13 C, δ18 O) isotopic compositions using a high-precision micro-scale isotopic analytical system (MICAL3c with IsoPrime 100). We successfully milled each daily ring with width ranging from 14.0 to 62.9μm (average 27.0μm) during the high growth period (30-70 days after hatching), and determined the isotopic compositions of otolith aragonite. Our improved micro-scale analytical method is the first to determine the daily δ18 O history of fish otoliths. By using our method together with the δ18 O - water temperature equation, the daily history of experienced water temperature can be elucidated. Our high-resolution milling and analytical technique can also be applied to high-resolution isotope analysis for stalactites, clams, and corals.

Daily otolith ring validation, age composition, and origin of the endangered striped catfish in the Mekong

The endangered striped catfish, Pangasianodon hypophthalmus is a large-bodied, migratory catfish, and one of the most cultured catfishes in the world. This study examines the otoliths of drifting wild-caught and hatchery-raised larvae of striped catfish to validate daily ring counts, calculate fish age, and estimate spawning time and spawning location to improve our understanding of the species’ life history. We conducted daily sampling of larval/juvenile striped catfish in the Mekong mainstream in Phnom Penh in 2015 and at a fish hatchery in Cambodia. Daily water levels and river distances at and between four hydrological gauges over the Mekong River reach between Phnom Penh and Cambodia-Lao border were also collected. Standard length and otolith ring counts were examined in both hatchery-raised (150) and wild-caught (390) samples. This study revealed that (i) mass larval drift of striped catfish at the Mekong River in Phnom Penh took place from July 13th to July 23rd, 2015 corresponding with increasing flow, (ii) otolith rings are formed daily in hatchery-raised larvae, and can be used to determine the age of wild larvae/juveniles, (iii) otolith ring increments are strongly correlated with standard length in hatchery-raised larvae, but not in wild-caught larvae, (iv) mean standard length and age of striped catfish larvae collected in Phnom Penh are 14.65 mm (se = 0.07) and 27.6 days (se = 0.13), respectively, and (v) most striped catfish likely spawn in June and early July between the full and new moon, and the spawning grounds are most likely located along the Cambodian Mekong between Stung Treng and Kratie and, in 2015, travel time from spawning grounds to Phnom Penh was approximately 27 days. Upper Cambodian Mekong River is therefore likely very necessary for the persistence of all striped catfish populations and fisheries in the lower floodplains of Cambodia and Mekong delta. The existing and proposed dams in the upper Mekong River in Cambodia and beyond would drastically affect spawning sites and dry season refuge habitats and disconnect the upstream spawning from the downstream rearing habitats of the species.

Validating a biophysical dispersal model with the early life-history traits of common sole (Solea solea L.).

Larval dispersal and juvenile survival are crucial in determining variation in recruitment, stock size and adult distribution of commercially important fish. This study investigates the dispersal of early-life stages of common sole (Solea solea L.) in the southern North Sea, both empirically and through modeling. Age at different life-history events of juvenile flatfish sampled along the coasts of Belgium, the Netherlands and the United Kingdom in 2013, 2014 and 2016, was determined through the counting of daily growth rings in the otoliths. Juveniles captured between August and October were estimated to be on average 140 days old with an average pelagic larval duration of 34 days. The hatching period was estimated between early April and mid-May followed by arrival and settlement in the nurseries between May and mid-June. Growth rates were higher off the Belgian coast than in the other nursery areas, especially in 2013, possibly due to a post-settlement differentiation. Empirical pelagic larval duration and settlement distributions were compared with the Larvae&Co larval dispersal model, which combines local hydrodynamics in the North Sea with sole larval behavior. Yearly predicted and observed settlement matched partially, but the model estimated a longer pelagic phase. The observations fitted even better with the modelled average (1995–2015) distribution curves. Aberrant results for the small juvenile sole sampled along the UK coast in March 2016, led to the hypothesis of a winter disruption in the deposition of daily growth rings, potentially related to starvation and lower food availability. The similarities between measured and modelled distribution curves cross-validated both types of estimations and accredited daily ageing of juveniles as a useful method to calibrate biophysical models and to understand early-life history of fish, both important tools in support of efficient fisheries management strategies.

A new perspective of Mugil liza: The fast growth in an impacted subtropical bay

Mugil liza is one of the most important fishery resources in west margin of Southwestern Atlantic. Its northern population (northward of 23°40’S) is distributed along the Brazilian coast and, including the Guanabara Bay (GB, 22°50’S, 43°10’W). This study aimed to evaluate the ring formation in the sagitta to estimate the fish age and growth. Based on monthly samplings (2011–2013), 815 individuals were caught (285–815 mm TL), and a subsample of 299 otoliths were analyzed. The otoliths were embedded, cross-sectioned and read in terms of “annual” rings (macrostructural analysis). Then, they were analyzed in terms of daily rings (microstructural analysis) and the deposition of calcium carbonate (ultrastructural analysis). The comparison among the three methods revealed that five macro rings are formed in the first year. Ulterior to this diagnosis, back-calculation and growth models were simulated and tested to describe the growth in the first year and the general growth pattern. The ages varied from 0.63- up to 5 years-old, with a high variability of total lengths by ages. The von Bertalanffy growth model based on back-calculated lengths of Dahl-Lea best described the growth pattern. Mugil liza at GB presented sexual dimorphism in terms of growth, females being longer and older, and it was revealed a fast growth pattern. These findings reinforce the identity of a probable stock of M. liza at GB and change drastically the current knowledge their age and growth. The regulatory marks for the species must be reviewed, at least for GB. The current results evidence the need of current assessment and monitoring of fisheries resources, identifying the patterns of population groups.

Evaluation of otolith microstructures for ageing of larval white sturgeon

Sturgeon populations are endangered worldwide, mainly due to habitat degradation and overexploitation causing recruitment failure. Understanding of early development, survival and growth in sturgeon is limited by a lack of a validated method to directly estimate larval age. In a laboratory calibration study, we reared white sturgeon (Acipenser transmontanus) larvae from hatch for 3 weeks at 12 and 16 °C and two feeding regimes (fed and unfed) to determine the usefulness of their vateritic microotoconia for larval ageing and the influence of environmental factors on ring structure and size. By marking the otoliths twice at known ages with Alizarin Red S, we were able to confirm the presence of daily rings in the largest microotoconia and the feasibility of ageing larval sturgeon using otoliths. Three observers blind to age and treatment assessed larval age from daily rings with an overall precision of 67%–82% and 30%–70% accuracy, dependent on larval age. Neither temperature nor feeding had a significant effect on ring width or readability. Thus, ageing sturgeon larvae using otolith microstructures is a promising tool for sturgeon conservation efforts.

Estimating the spawning and growth of striped snakehead Channa striata Bloch, 1793 in Lake Rawa Pening Indonesia

The striped snakehead (Channa striata Bloch, 1793) is a commercially important fish in Lake Rawa Pening, central Java, Indonesia. This study aims were to investigate their age, growth, and recruitment pattern, through a sampling that was performed monthly, from November 2017 to August 2018. The individual fish was measured for length and weight, and sex was determined. The otoliths were collected, cleaned, and placed on molds to pour epoxy resin. The otoliths were cut to obtain slices and observed under a microscope at 100 × magnification. Subsequently, the age was determined by counting the number of daily rings. It was established that the snakehead spawned every month, with a comparably higher frequency in the new moon than in other phases, and mostly were 3–10 months old, characterized by bigger and older sizes during the rainy season. Furthermore, the average growth rate was observed to be faster during the rainy season in contrast with the dry season. Hence, the parameters of von Bertalanffy growth functions were estimated by back-calculated length, and the pattern in female was Lt = 56.09 (1 − e− 0.81 (t + 0.07)), while male Lt = 59.36 (1 − e− 0.71 (t + 0.09)), and total Lt = 60.32 (1 − e− 0.71 (t + 0.14)), respectively.

Coastal wetland restoration improves habitat for juvenile sportfish in Tampa Bay, Florida, U.S.A.

Increasing human populations and urban development have led to losses of estuarine habitats for fish and wildlife. Where resource managers are restoring coastal wetlands, in addition to meeting goals related to hydrologic connectivity, biodiversity, and recreational opportunities, efforts are being made to provide habitat that is suitable for juvenile sportfish. An 18-month study was conducted to compare juvenile sportfish use of natural, restored, and impacted sites along Tampa Bay, Florida, shorelines. Juvenile sportfish densities at restored sites were broadly comparable to natural sites and greater than at impacted sites. However, site-specific differences in sportfish use did occur within site types. For example, one restored site had significantly higher densities of red drum Sciaenops ocellatus than any other site, while black drum Pogonias cromis were found exclusively at another restored site. To evaluate whether the restored sites are providing suitable habitat for juvenile fish, we assessed growth (estimated from counts of daily rings on otoliths) and condition (determined by lipid analyses) of juvenile common snook Centropomus undecimalis, an archetypal coastal wetland-dependent species. Growth (0.43–0.56 mm SL/day) and condition (4.6–6.1% lipid of dry weight) exhibited only site-specific differences and did not vary among natural, restored, and impacted site types. Although mortality rates of juvenile sportfish were not determined, use of a 40-m seine found that densities of potential piscine predators in these coastal wetlands were relatively low compared to published studies of open estuarine shorelines. The restoration and creation of coastal wetlands in Tampa Bay provides improved habitat for juvenile sportfish.

Age and growth of stocked juvenile Shoal Bass in a tailwater: Environmental variation and accuracy of daily age estimates.

Otolith microanalysis is often used to assess population age structure and growth of fishes during their early stages. Shoal Bass Micropterus cataractae is a recently described species of conservation concern and little is known regarding factors affecting their recruitment. In 2004, Georgia Department of Natural Resources (GADNR) and the US National Park Service (NPS) stocked Shoal Bass marked with oxytetracycline (OTC) in the Chattahoochee River near Atlanta, Georgia in an effort to restore this population, creating known-age fish to examine the effect of environment on daily age accuracy. We obtained samples of stocked juvenile (<150 mm) Shoal Bass from standard monitoring that occurred approximately 30–60 days after stocking in the Chattahoochee River to 1) validate daily rings for estimating age, hatch dates, and growth rates for stocked age-0 Shoal Bass, and 2) evaluate the effect of habitat (location) on age bias. Shoal Bass otoliths were examined for OTC marks and daily rings were counted in reference to OTC marks to assess age estimation accuracy. Age estimation accuracy ranged from -2 to -25 days and was influenced by the environment where Shoal Bass were captured, with greater inaccuracy in colder water temperatures. Fish collected from locations with colder temperatures displayed closer spacing of daily rings, potentially leading to greater underestimation of age. Growth rates of stocked Shoal Bass, corrected for age estimation error, ranged from 0.5 mm/day to 0.8 mm/day. This study demonstrates the effect of environmental variability on age inaccuracy and subsequent interpretation of results. Incorporating methods to assess age estimation accuracy is needed to understand interspecific differences in recruitment among black bass species in the variety of natural and human-modified environments they inhabit.

Posthatch Development of Otoliths and Daily Ring Genesis in Age‐0 Spotted Gars

AbstractGars (Lepisosteidae) are increasingly being managed as top‐level predators that are important to overall ecosystem health. Given the paucity of information on early life history for many species, additional early life history data would aid in gar conservation and management. Daily rings in otoliths are useful for determining many early life history parameters, such as growth rates and the date of hatch, but properly interpreting these structures requires additional information on otolith formation. Gars represent an ancient lineage, and their otoliths are unlike those of most teleost fishes, having multiple nuclei and being covered on the surface with very small otoconia. We used computed tomography X‐ray scanning and oxytetracycline (OTC) marking of a series of known‐age fish from hatch through 10–12 d posthatch (dph) to understand the formation of otoliths in the Spotted Gar Lepisosteus oculatus, a species that is of management concern in several parts of its range in North America. The sagittae and lapilli each began as loose associations of otoconia at hatch; they fused and hardened into single crystals by 4 dph, in concert with the transition from attached larvae to free‐swimming juveniles. Asteriscus otoliths were not observed in any of the individuals examined through 12 dph. The OTC marks were not observed on individuals treated at hatch, and variable marks were detected at 1–5 dph. By 6 dph, 100% of individuals exhibited OTC marks on sagittae and lapilli. Daily rings could not be discerned until fish were marked at 4 dph, after which daily age estimates increased linearly with fish age. Results of this study verify that in Spotted Gars, otoliths (sagittae and lapilli) and their daily rings form several days after hatch, in relation to the transition from sessile, attached larvae to free‐swimming juveniles.

Digital Imaging Tool to Enhance Otolith Microstructure for Estimating Age in Days in Juvenile and Adult Fish

Age estimation based on fish otolith microstructure analysis is a very repetitive and time-consuming task. The lack of appropriate image analysis software, capable of both overlaying a number of images automatically and recording a high number of daily increments, has been a significant limitation in counting and measuring daily growth increments in large otoliths from juvenile and adult fish individuals. This paper presents a new software to assist marine biologists with faster, more efficient, and more reliable microstructure readings of fish otoliths. Open source code is preferred so that software packages can be updated with new image processing algorithms developed by the scientific community. The approach consists of three steps: 1) a single grayscale digital image combining images of different parts of the same fish otolith is obtained using the blind image registration technique fast normalized cross correlation; 2) the growth rings of the image are enhanced for age estimation purposes, using the adaptive histogram equalization technique; and 3) a semiautomatic interactive tool draws a simple polygonal chain along which the microstructures are easily identifiable and the points of interest can be marked, whose data will be saved automatically. This new tool opens up the opportunity of aging juvenile and adult fish individuals at regular intervals by counting growth rings in the otolith microstructure and facilitates working with other calcified pieces of marine species that exhibit a daily ring pattern, such as cephalopod beaks and mollusk shells.

An accurate tool for ageing Two‐spined Blackfish for use in determining timing of spawning in upland streams in the Brindabella ranges, ACT, Australia

SummaryTo manage populations of threatened fish species in modified habitats and regulated rivers requires an understanding of their reproductive biology and spawning cues. In particular, accurate information about early life stages in these species can be used to facilitate programmes that maximise recruitment and breeding success. This study aimed to develop methods to accurately age early juvenile freshwater native fish, Two‐spined Blackfish, (Gadopsis bispinosus), to allow the determination of spawning date. This was accomplished through the examination of otolith microstructure in early juveniles. The age at which the first ring was deposited and the relationship between days and number of rings were determined using both field and aquarium trials. Field trials of marked juvenile otoliths revealed daily deposition of rings (1.02 ± 0.02 rings per day for fish sacrificed six days postmarking). The strength of this relationship lessened slightly as juveniles aged (0.92 ± 0.02 rings per day for fish sacrificed 13 days postmarking). The first otolith ring was deposited 7.50 ± 1.09 days after spawning. The enumeration of daily rings combined with knowledge of the commencement of ring deposition enabled accurate estimation of spawning date. The current study is the first to examine otolith microstructure in juvenile Two‐spined Blackfish allowing accurate determination of spawning date. While more research is required to accurately age older juveniles, this technique has the potential to precisely correlate spawning with environmental cues, facilitating better management of temperature and flow during breeding periods, potentially increasing spawning and recruitment of this endangered species.

Location of lens pigment with etafilcon a daily disposable limbal ring hydrogel contact lenses and the effect on coefficient of friction

s / Contact Lens & Anterior Eye 38 (2015) e13–e46 e23 with etDD were clinically equivalent to that observed with NL. Conjunctival hyperaemia and corneal staining were also clinically unremarkable under both conditions. These results confirm that etDD CLs minimally impact corneal physiology during normal open-eye wear. AmirMoezzi is a clinical scientist at the Centre for Contact Lens Research (CCLR). He completed his Optometry training in Iran and his Master’s degree at the CCLR, University of Waterloo. He then joined the CCLR research team in 2003 and has been extensively involved in thefieldof clinical contact lens research, focusingon the corneal physiological response to contact lens wear. He has completed a number of studies in this field and presented in scientific journals and meetings. Amir is a registered member of the College ofOptometrists of Ontario and amember of theOntario Association of Optometrists. http://dx.doi.org/10.1016/j.clae.2014.11.025

Age determination and validation on otoliths for two sympatric species, Mullus barbatus (Linnaeus, 1758) and Mullus surmuletus (Linnaeus, 1758), in the Adriatic Sea

Event Abstract Back to Event Age determination and validation on otoliths for two sympatric species, Mullus barbatus (Linnaeus, 1758) and Mullus surmuletus (Linnaeus, 1758), in the Adriatic Sea Sanja Matić-Skoko1*, Josipa Ferri2, Nika Stagličić1, Branko Dragičević1, Jakov Dulčić1, Pero Tutman1 and Dajana Brajčić Jurica3 1 Institute of Oceanography and Fisheries, Croatia 2 University of Split, Center of Marine Studies, Croatia 3 Fishermen Cooperative Fresh Fish, Croatia In last few years, there is a strong need to establish a reliable method for age determination and validation on otoliths for Mullidae species in the Mediterranean Sea. In total, 387 specimens of Mullus surmuletus (TL 6.8 to 32.9 cm) and 620 specimens of M. barbatus (TL 8.1-22.0) were analyzed. The annual periodicity of annulus deposition was supported by the otolith marginal increment analysis. The annual growth was verified using edge-type analysis. The proportion of otoliths with opaque margins was the highest (>80%) in the winter period (December-March). The monthly mean marginal increment showed a single minimum in May and June for M. barbatus and M. surmuletus, respectively. Age validation was done by daily ring counting. A distance measurements analysis revealed that first regular ring appears at distance of 0.78 mm (± 0.104 SD) from otolith nucleus and fish age of about 0.83 years for M. surmulets. For M. barbatus first ring appear at 0.70 mm ((± 0.100 SD) at age of 0.92 years. The age analysis revealed 4 and 6 age classes for M. barbatus and M. surmuletus, respectively. Predominance of younger age classes (1+ and 2+) was observed for both species. All measured otolith morphometric parameters were linear with fish age. The most precise age estimations were obtained from the otolith width, followed by the otolith length and mass. The growth parameters were estimated by the fit of the Von Bertalanffy growth function. Although, the growth of both species was rapid up to 2 years of age and then slowed, M.barbatus exhibited faster growth. Considering the identified biological differences and their implications, existing management should be complemented by a more holistic, ecosystem approach to regulations, considered separately for each species in order to assure effective conservation measures for this economically and ecologically important fish species. Keywords: age, otholits, Mullidae, Determination, Validation Conference: XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015. Presentation Type: Poster Presentation Topic: Otoliths as a tool to study fish life cycles Citation: Matić-Skoko S, Ferri J, Stagličić N, Dragičević B, Dulčić J, Tutman P and Brajčić Jurica D (2015). Age determination and validation on otoliths for two sympatric species, Mullus barbatus (Linnaeus, 1758) and Mullus surmuletus (Linnaeus, 1758), in the Adriatic Sea. Front. Mar. Sci. Conference Abstract: XV European Congress of Ichthyology. doi: 10.3389/conf.FMARS.2015.03.00174 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: 28 Oct 2015; Published Online: 28 Nov 2015. * Correspondence: Dr. Sanja Matić-Skoko, Institute of Oceanography and Fisheries, Split, Croatia, sanja@izor.hr 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 Sanja Matić-Skoko Josipa Ferri Nika Stagličić Branko Dragičević Jakov Dulčić Pero Tutman Dajana Brajčić Jurica Google Sanja Matić-Skoko Josipa Ferri Nika Stagličić Branko Dragičević Jakov Dulčić Pero Tutman Dajana Brajčić Jurica Google Scholar Sanja Matić-Skoko Josipa Ferri Nika Stagličić Branko Dragičević Jakov Dulčić Pero Tutman Dajana Brajčić Jurica PubMed Sanja Matić-Skoko Josipa Ferri Nika Stagličić Branko Dragičević Jakov Dulčić Pero Tutman Dajana Brajčić Jurica 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.

Validation of Daily Ring Deposition in the Otoliths of Age-0 Alligator Gar

Abstract We validated techniques for estimating the daily age of young-of-the-year Alligator Gar, Atractosteus spatula. Alligator Gar eggs were hatched and larvae were grown in aquaria and then transferred to an outdoor artificial stream. Fish were sampled from 21 d to 118 d posthatch. Sagittal otoliths were extracted from each fish, and each otolith was embedded in a clear epoxy resin. Otoliths were sectioned along a transverse plane, sanded with 600-grit sandpaper to reveal daily rings, and then polished with 1500-grit sandpaper. We estimated the daily age of each otolith three times, making each estimate in random order without reference to known ages. The mean of the three counts for each otolith was considered the final age estimate. Daily age estimates of 50 Alligator Gar (21–118 d old, 43–458 mm total length) were closely related to known fish ages, validating daily ring deposition. Absolute error in age estimates increased after 62 d posthatch; 68% of the estimated ages were within ±3 d of the known age through 62 d, whereas only 26% of the estimated ages were within ±3 d of the known age from 76 to 118 d posthatch. However, mean estimates for each cohort were within 5 d of known age through 104 d posthatch. Daily increments near the core were difficult to identify, but later increments were more discernable and deposited in a regular pattern. A significant relationship was also identified between fish total length and otolith radius (P &amp;lt; 0.01), indicating that estimates of growth histories should be reliable. We encourage researchers to utilize our aging technique to estimate hatch dates, the timing and frequency of hatching, and early growth rates of Alligator Gar in wild populations. This early life history information will be valuable in enhancing management and conservation of this species. Received March 21, 2014; accepted July 16, 2014

A simple method to assess the marine environment residence duration of juvenile sockeye salmon (Oncorhynchus nerka) using laser ablation

Monitoring habitat utilization and early marine growth of sockeye salmon juveniles (Oncorhynchus nerka) in fjords of the Pacific Northwest is currently hampered by difficulties in estimating residence times, limiting scientific advances in certain aspects of this species’ fisheries management and conservation. Combining otolith microchemistry and conventional daily ring counts, we were able to obtain the date of first entry and the residence time of sockeye juveniles in Rivers Inlet, British Columbia. This operationally inexpensive method builds upon variable microelement concentrations in fresh- and saltwater environments: barium (Ba) and strontium (Sr) concentrations within the sockeye otoliths differed between the freshwater and seawater growth zones; Ba concentrations in the freshwater growth zone were significantly higher than those in the seawater growth zone, while Sr concentrations in the former were significantly lower than in the latter. The concentrations of these elements within otoliths were determined quantitatively at high spatial resolution using in situ laser ablation inductively coupled with a plasma mass spectrometer (ICPMS) providing a record of the ambient environmental conditions experienced by individual fish. Exploratory analysis of a 3-year data set showed that the mean residence time of sockeye juveniles in Rivers Inlet varied between 3 and 6 weeks between years.

Atomic force microscopy and scanning electron microscopy analysis of daily disposable limbal ring contact lenses

BackgroundLimbal ring (also known as ‘circle’) contact lenses are becoming increasingly popular, especially in Asian markets because of their eye‐enhancing effects. The pigment particles that give the eye‐enhancing effects of these lenses can be found on the front or back surface of the contact lens or ‘enclosed’ within the lens matrix. The purpose of this research was to evaluate the pigment location and surface roughness of seven types of ‘circle’ contact lenses.MethodsScanning electron microscopic (SEM) analysis was performed using a variable pressure Hitachi S3400N instrument to discern the placement of lens pigments. Atomic force microscopy (Dimension Icon AFM from Bruker Nano) was used to determine the surface roughness of the pigmented regions of the contact lenses. Atomic force microscopic analysis was performed in fluid phase under contact mode using a Sharp Nitride Lever probe (SNL‐10) with a spring constant of 0.06 N/m. Root mean square (RMS) roughness values were analysed using a generalised linear mixed model with a log‐normal distribution. Least square means and their corresponding 95% confidence intervals were estimated for each brand, location and pigment combination.ResultsSEM cross‐sectional images at 500× and 2,000× magnification showed pigment on the surface of six of the seven lens types tested. The mean depth of pigment for 1‐DAY ACUVUE DEFINE (1DAD) lenses was 8.1 μm below the surface of the lens, while the remaining lens types tested had pigment particles on the front or back surface. Results of the atomic force microscopic analysis indicated that 1DAD lenses had significantly lower root mean square roughness values in the pigmented area of the lens than the other lens types tested.ConclusionsSEM and AFM analysis revealed pigment on the surface of the lens for all types tested with the exception of 1DAD. Further research is required to determine if the difference in pigment location influences on‐eye performance.

Within-otolith variability in chemical fingerprints: implications for sampling designs and possible environmental interpretation.

Largely used as a natural biological tag in studies of dispersal/connectivity of fish, otolith elemental fingerprinting is usually analyzed by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). LA-ICP-MS produces an elemental fingerprint at a discrete time-point in the life of a fish and can generate data on within-otolith variability of that fingerprint. The presence of within-otolith variability has been previously acknowledged but not incorporated into experimental designs on the presumed, but untested, grounds of both its negligibility compared to among-otolith variability and of spatial autocorrelation among multiple ablations within an otolith. Here, using a hierarchical sampling design of spatial variation at multiple scales in otolith chemical fingerprints for two Mediterranean coastal fishes, we explore: 1) whether multiple ablations within an otolith can be used as independent replicates for significance tests among otoliths, and 2) the implications of incorporating within-otolith variability when assessing spatial variability in otolith chemistry at a hierarchy of spatial scales (different fish, from different sites, at different locations on the Apulian Adriatic coast). We find that multiple ablations along the same daily rings do not necessarily exhibit spatial dependency within the otolith and can be used to estimate residual variability in a hierarchical sampling design. Inclusion of within-otolith measurements reveals that individuals at the same site can show significant variability in elemental uptake. Within-otolith variability examined across the spatial hierarchy identifies differences between the two fish species investigated, and this finding leads to discussion of the potential for within-otolith variability to be used as a marker for fish exposure to stressful conditions. We also demonstrate that a ‘cost’-optimal allocation of sampling effort should typically include some level of within-otolith replication in the experimental design. Our findings provide novel evidence to aid the design of future sampling programs and improve our general understanding of the mechanisms regulating elemental fingerprints.

Age, growth and utility of otolith morphometrics as a predictor of age in the wrasse &lt;i&gt;Coris julis&lt;/i&gt; (Labridae) from the eastern Adriatic Sea

Age and growth of Coris julis were determined by examining sagittal otoliths belonging to fish sampled between November 2008 and October 2009 in the eastern Adriatic Sea (north-central Mediterranean Sea). A total of 1102 specimens (528 males, 487 females and 87 individuals of indeterminate sex), ranging from 48 to 222 mm total length were analysed. Ninety-two per cent of the otoliths were readable and 68% of the specimens had two readings in agreement. Counting of daily rings revealed that the second opaque ring represents the first annulus (315.1±27.8 daily rings). The maximum observed age was 7 years for males and 5 years for females, with males dominating in higher age classes ( > 3 years) and females in age classes 1+ and 2+. Growth was described by the von Bertalanffy growth curves and significant differences were found between males (L∞=29.10 cm, k=0.12 and t0=–1.48) and females (L∞=21.27 cm, k=0.21 and t0=–1.08). Otolith mass, length, width and thickness were determined for the otoliths belonging to 465 fish and the utility of these morphometrics as a predictor of age was evaluated. The most precise age estimations were obtained from the otolith length data, followed by the otolith mass.