Modern Protocols, Procedures, and Analytical Tools for Determining Age and Growth of Free-Ranging Animals


8:00AM Quality Control and Quality Assurance Processes Used in Thermal-Mark Recovery in Southeast Alaska
  Beverly Agler
Alaska Department of Fish and Game (ADF&G) has used otolith thermal marking of hatchery-raised salmonids since 1994 to distinguish stocks and assist with fishery management. ADF&G Statewide Mark lab processes ~20,000-30,000 otoliths each year. Thermal-marked fish typically are not given a secondary mark, so multiple readings among readers and geographic areas are used to estimate reader ability to detect a mark and to calculate agreement of identifications. Because there are no “knowns,” Mark Lab staff blind second read 40-100% of samples. We compare first and second reads with an agreement matrix to determine whether there are problems in reader training or marks that might need to be re-examined. We then use the kappa statistic to examine overall agreement between readers and agreement by specific mark. At a project’s end, we estimate error rates of each reader using latent class models, because, although useful, kappa statistics are influenced by the true proportion of marked fish. Analyzing mark results in this manner ensures quality control among projects and a measure of accuracy of thermal mark recoveries of sampled fish. If data were left uncorrected, errors in identifications could affect management by altering population estimates.
8:20AM A Problem for the Ages: Quality Assurance and Control Techniques Used to Obtain Reliable Age Structure Information
  Micah Davison
Information reliability is directly related to data quality. The Nampa Research Anadromous Ageing Laboratory provides age information on threatened and endangered Idaho salmonids to multiple state, tribal, and federal agencies. This information is based on the interpretation of calcified structures, specifically fin rays and scales, and associated biometric data. A critical component of our operation is the quality assurance and control protocols designed to minimize error and their consequences while efficiently utilizing limited resources. Here we discuss three key process phases: collection, interpretation, and distribution. For each we have developed quality control procedures to maximize information quality and reliability. We implemented training protocols to standardize competencies across each process phase and maintain quality standards. Pattern variability across species, life stage, space and seasons are a major source of potential error. In order to acclimate readers to seasonal pattern variability in saltwater ages and assess reader accuracy, samples of known age are read before the main workload. For juvenile samples, we constructed past seasonal summaries, which are reviewed prior to ageing samples from each location. The combination of seasonal calibration with post hoc analysis, such as length-at-age outliers, provides effective quality control that can be adapted to any ageing program.
8:40AM Is There Variability Among Scale Age Estimates of Chinook Salmon in Alaska?
  Beverly Agler
Salmon management includes estimating age of returning fish from scales. Alaska Department of Fish and Game (ADF&G) regional offices have developed scale age methods, but procedures are often undocumented, leading to inconsistent age estimates negatively impacting management. ADF&G held a workshop in Juneau, AK to compare procedures to estimate age of Chinook salmon in the Pacific Northwest and discuss possible standardization. To continue this work, funding from Saltonstall-Kennedy program was used to compared variability in Chinook salmon scale ages across Alaska. Readers (n=10) estimated age of 10,200 images of Chinook scales using an online application. Participants attended a workshop to review results and develop guidelines. Salmon Scale Wiki, an interactive website, was one outcome of this workshop. Study results included no variability among three time periods. Small, overlapping variability was observed among five geographically-distinct stocks. Overall, variability among age estimates was within expected parameters at 6.3%. Variability was highest for younger fish. This demonstrated importance of learning scale patterns of young fish when learning to age Chinook salmon. We incorporated the variability into simulations to examine effects on management parameters, and preliminary results indicated population estimates would be affected when harvest rate was high.
9:00AM Utilizing the Image-Pro Otolith APP to Easily Analyze Otolith and Scales
  Rick Logemann
A leader in the digital imaging analysis for over 35 years, Media Cybernetics has developed solutions that have been applied across many industries. Engineering products for researchers to deliver better and more consistent results. The latest version of software Image-Pro carries on this philosophy by improving our macro language as well as a user-friendly APP development tool, resulting in a flexible solution. The Image-Pro Otolith APP is one example of those solutions. Powerful analysis engineered into an easy to use workflow is also adaptable to your needs. Work directly with Media Cybernetics engineers to develop your own APP. Discover how the flexibility and functionality can be utilized in your lab to easily accelerate your research.
9:20AM The Use of PIT Tags and GSI to Validate Ages Estimated from Scales of Salmonids Collected at Bonneville Dam
  Jeffrey K. Fryer
Salmonids have been trapped at Bonneville Dam since 1985 and scale sample to estimate age composition of Sockeye, Chinook, and steelhead. Until recently, age validation was not possible since all fish were of unknown age. With increasing numbers of juvenile salmonids being PIT tagged (though returns typically comprise less than 1% of adults sampled), it has become possible to compare scale ages with age since PIT tagging. Also, advances in genetic stock identification techniques, most notably Parental Based Tagging (PBT), have provided age data on up to 30% of steelhead and Chinook sampled. Corroboration between both PIT-tag and PBT-derived ages and scale ages have consistently been above 95%. With faster turnaround of genetics samples (generally within two weeks from sampling), we have switched from reviewing PBT data post-season and adjusting scale ages to waiting until PBT data is available prior to scale ageing. This allows us to incorporate PBT age data (and information on scale patterns gleaned from those PBT ages) into the scale ageing process, resulting in more accurate ageing with less time spent.
09:40AM Break
1:10PM The Use of Multiple Techniques to Validate Ages from Naturally Reproducing Steelhead
  Carlos Camacho
The ability to assign accurate ages using non-lethal structures is vital to calculate cohort productivity for species with a wide range of life histories that are at low abundances. Validation of scale ages with reliable, independent methodologies at each life history stage is not easily obtained for many species, such as naturally reproducing steelhead. However, advancements in tag technology and the development of genetic “tags” have expanded age validation opportunities. In this paper, we use PIT (passive integrated transponder) tags and PBT (parental based tag genotyping) to validate the saltwater, freshwater, and total ages from steelhead scales in two related studies. In the first study, scale saltwater ages were in agreement with 96% of the PIT tag ages. In the second study, scale freshwater ages were in agreement with 93% of the PBT ages. Scale total ages were in agreement with 90% of the PBT total ages. Comparing both studies shows that most of the uncertainty in total age assignments comes from the freshwater phase. Using multiple techniques to validate assigned ages is possible for steelhead in the Snake River basin and having reliable ages provides a crucial piece of information needed to assess population viability and status.
1:30PM Improvements to Coho Salmon Scale Ageing in Southeast Alaska
  Justin T. Priest
Accurate ageing of fish stocks is fundamental to age-structured stock assessment of salmon populations. Stocks of Coho Salmon Oncorhynchus kisutch in Southeast Alaska are aged using circuli in scales and historically were difficult to age because of unique environmental conditions causing thermal abnormalities. To determine known ages of wild Coho Salmon stocks in Berners River and Hugh Smith Lake, Alaska, emergent fry were tagged with half-length coded-wire tags and recovered 1–3 years later during smolt outmigration, 1995–2005. Smolt scales were collected and paired with tag release data. Results demonstrated that agers had consistently over-aged Coho Salmon from these systems prior to study initiation; visual assessment of known-age scale patterns now guides age determination to improve accuracy. Recent improvements in computer software have allowed these known-age smolt scales to be digitized then overlaid with estimates of circuli distances and freshwater age zones. Analysis of circuli measurements and smolt length was performed using Quadratic Discriminate Analysis to predict freshwater smolt ages and evaluated using the known ages. Model results show a high accuracy (>90%) for both stocks. Future use of this model can improve ageing performance and automate ageing processes, allowing for more effective management strategies of wild salmon populations.
1:50PM Evaluation of Dorsal Fin Rays and Spines As a Non-Lethal Ageing Method for Goliath Grouper Epinephelus Itajara
  Jessica Carroll
Atlantic Goliath Grouper Epinephelus itajara is the largest grouper in the western North Atlantic, and it exhibits life history characteristics that make it particularly susceptible to fishing pressure. In 1990 a harvest moratorium for Goliath Grouper in US waters was enacted, which created a data-poor environment from which to assess the stock status. Biological data, particularly fish ages, are needed to estimate population parameters for stock assessments. Otoliths, the typical structure processed for age determination, are unavailable from Goliath Grouper because of their protected status. Structures that can be obtained non-lethally, such as dorsal fin rays or spines, may provide a viable alternative for ageing. The Florida Fish and Wildlife Conservation Commission (FWC) has been collecting incidental Goliath Grouper samples from mortality events since 2006. Corresponding otolith, dorsal fin ray and dorsal spine samples from 77 fish were compared to determine the accuracy of these alternative ageing structures. The fish in this dataset range in age from 2–35 years (otolith age), and in size from 566–2244 mm TL. This research will inform biological sampling methodology for Goliath Grouper ageing structures and could directly impact the stock assessment, and potentially, the determination of recovery of the species.
2:10PM Utility of Otoliths, Scales, Fin Rays, and Opercles in Estimating the Age Structure of a Population of Blue Suckers
  Dakota Radford
Blue Suckers (Cycleptus elongatus) are distributed throughout the Mississippi-Missouri watershed. Of the twenty-three states they have occurred in they are listed as extirpated from one, endangered in one, threatened in four, and a species of concern in seven. The difficulty in sampling Blue Suckers, combined with their low monetary value in modern fisheries, has resulted in a shortage of research addressing this native species. The lack of research has limited conservation efforts at the state and federal level. We aim to inform Blue Sucker research and conservation by comparing the ease, associated mortality, and precision between four hard structures (otoliths, scales, pectoral fin rays, and opercles) used in estimating specimen age. Our comparison of aging structures is based on Blue Suckers collected in 2018 from an un-impounded Midwestern river (n=68). Specimens ranged in total length from 275-679 mm (average TL = 609.5 mm), with a conspicuous absence of juvenile samples. The age-structure, mortality rate, maximum length, and growth curve for this population will be compared to published demographics of other Blue Sucker populations. Ultimately, the demographic assessment of this population will augment the growing body of research addressing Blue Suckers and their status.
2:30PM On the Age and Growth of Deep-Pelagic Fishes, with Case Studies of the Top Predators Omosudis lowii, Stomias affinis, and Chauliodus sloani
  Natalie Slayden
Deep-pelagic fishes provide important ecosystem services, such as carbon sequestration via the biological pump and prey provisioning for species targeted by fisheries (e.g., tuna, billfishes) and federally protected species (e.g., toothed cetaceans, seabirds). These services are becoming increasingly appreciated, even as mesopelagic fisheries are becoming of interest as coastal fisheries have become overexploited. In addition to emerging fisheries, climate change, ocean acidification, and seabed mining threaten deep-pelagic fishes. With increasing threats, age and growth information on deep-pelagic fishes is critical for management and conservation. The majority of age and growth studies to date have focused on the family Myctophidae (lanternfishes) due to their presumed importance in food chains; most other taxa remain relatively uninvestigated. In order to address these information gaps, age estimations and otolith microincrement descriptions linked to life histories will be presented on the top-predator fish species Omosudis lowii, Stomias affinis, and Chauliodus sloani. These fishes were collected from the northern Gulf of Mexico during seven research cruises from 2010–2011 (Offshore Nekton Sampling and Analysis Program) and during six research cruises from 2015–2018 (DEEPEND Consortium). Incorporating lifespan and growth rate estimations into ecosystem models provides critical data needed to manage and conserve burgeoning oceanic fisheries.
2:50PM Refreshment Break
3:20PM Preliminary Analysis of Tripletail (Lobotes surinamensis) Age and Growth in the North-Central Gulf of Mexico
  Amanda Jefferson
Tripletail (Lobotes surinamensis) are migratory fish occupying tropical and subtropical waters worldwide. In the Western Atlantic Ocean and Gulf of Mexico, tripletail are increasingly targeted by recreational anglers. Previous age and growth studies have drawn conflicting conclusions concerning the use of tripletail otoliths for aging. The most recent Gulf of Mexico tripletail age and growth study used samples collected two decades ago; moreover, Gulf of Mexico tripletail age and growth has never been modeled. Therefore, this study aims to 1) evaluate first dorsal spines and otoliths as aging structures and 2) model Gulf of Mexico tripletail age and growth. From 2012 to 2018, tripletail (n = 208) were collected from the north-central Gulf of Mexico via hook-and-line. The first dorsal spine and both otoliths were extracted from each fish for aging. Tripletail ranged in size from 403–780 mm total length, with females significantly larger than males (D = 0.18, p = 0.02). The M:F ratio was 0.64:1 and significantly differed from a 1:1 ratio (X2 = 9.78, df = 1, p < 0.01). Findings from this study will inform management and help ensure the sustainability of Gulf of Mexico tripletail despite increased popularity among, and pressure from, recreational anglers.
3:40PM Age and Growth of Atlantic Chub Mackerel (Scomber colias) in the Northwest Atlantic
  Taylor T. Daley
The Atlantic chub mackerel (Scomber colias) is commercially exploited throughout the Atlantic and Mediterranean and has been recently targeted by a small, but emerging, fishery off the Northeast coast of the US. Recent management efforts have necessitated the description of its life-history characteristics. We evaluated the utility of ageing methods and found that whole otoliths provided the most precise method for age determination. Age estimates were derived for adult (n = 422) and larval fish (n = 60). Parameter estimates of individual growth models were determined using a Bayesian framework. The length-at-age relationship was described using four non-linear candidate growth models, which were fit to total length (TL, cm) and age estimates (y). The three-parameter VBGF (L∞ = 33.56 cm TL, k = 1.75 y-1, t0 = 0.07 y) was selected as the best candidate model. A power function was used to describe the weight-at-length relationship from 1,136 individuals (a = 0.0258, b = 2.72). Compared to published estimates in other regions, individuals exhibited a greater rate of growth and reached smaller average maximum length, and the rate of increase of weight relative to length was significantly lower. These results can be used to inform assessment in the Northwest Atlantic.
4:00PM Age and Growth of Yellowfin Tuna (Thunnus albacares) from the Northwest Atlantic and Gulf of Mexico
  Ashley Pacicco
Biological information derived from direct ageing methods is limited for Yellowfin Tuna Thunnus albacares. During 2004-2017, a total of 3,223 sagittal otoliths were collected from fishery-dependent and fishery-independent sources in the Gulf of Mexico (n=3,055) and the U.S. Atlantic (n=168). Yellowfin Tuna lengths ranged from 609 -1981 mm curved fork length (CFL). Age was determined by counting opaque zones in transversely sectioned sagittal otoliths. Ages ranged from 1 to 18 years, with 95% age 5 and younger. Fish 10-18 years old made up 2% of ages and were older than those reported from previous studies. The growth model with the most parsimonious fit to the age data was the Gompertz (L∞ =1606, Gi=0.4, t0=-0.11), followed by the logistic (L∞ =1580, Gi=0.5, t0=0.7) and the von Bertalanffy (L∞ 1647, k=0.29 t0=-1.44), suggesting that yellowfin tuna have indeterminate growth. Male and female growth curves were significantly different for all three candidate models (P≤0.001), with males obtaining a greater size than females which is consistent with previous studies. Increased sampling of Yellowfin Tuna from the pelagic longline fishery is needed throughout the northwest Atlantic to better represent growth of larger fish targeted by that fishing sector.
4:20PM Age Determination of Bullseye Pufferfish Using Farmed and Wild-Caught Fish Data.
  Hugo Aguirre
The age and growth of bullseye pufferfish: Sphoeroides annulatus (Jenyns, 1842) was studied by analyzing vertebral samples. Samples were collected from specimens captured by artisanal fisheries between January 2014 and December 2016, with sizes ranging from 67 to 435 mm total length (TL), because specimens less than 100 mm TL were not well represented, 120 cultured organisms were collected between October 2016 and August 2017, with sizes ranging from 60 to 130 mm, 5 to 15 months old respectively. A total of 901 vertebrae were analyzed. The periodicity was annual, it was validated using the marginal increment method and the periodicity of growth band pairs. Two growth models were fitted to the age data, a three-parameter von Bertalanffy growth function (VBGF) and a two-parameter VBGF with a fixed L0 = 58 mm (average TL of culture organisms at age of 5 months). The latter was considered the most adequate to describe the growth of the species, with the estimated parameters being L∞ = 450 mm TL, k = 0.21 year−1 for combined sexes. Nine age groups from 0 to 8 were observed, the maximum age estimated was 13 years.
4:40PM Factors Affecting the Recruitment of Non-Native Smallmouth Bass in the Yellowstone River and Implications for Upstream Range Expansion
  Nick Voss
Non-native smallmouth bass were thought to be limited to the warm, downstream waters of the Yellowstone River (Montana), but adults were recently observed far upstream in coldwater reaches that support a major trout fishery. We sought to identify the factors that determine their current and future establishment (i.e., successful recruitment) in the upper Yellowstone River. We hypothesized that reduced age-0 growth potential in upstream reaches limits recruitment through size-selective overwinter mortality, and tested this hypothesis by sampling age-0 individuals across a broad longitudinal extent from 2016 to 2019 to describe their distribution, size at the onset of winter, thermal experience, diet, and otolith-inferred hatch dates and growth rates. The upstream extent of age-0 fish was 111 to 145 RKM downstream of that of adults. Median size at the onset of winter was not significantly different across the study area. Comparative hatch dates, growth rates, and growth durations were also counter to our predictions. These results suggest that age-0 overwinter mortality is not currently preventing upstream establishment in the Yellowstone River. We consider our results in the context of invasion ecology as well as broader patterns in water temperature, discharge, and fish assemblage composition.

Organizers: Jeffrey K. Fryer, Beverly Agler, Carlos Camacho, Timothy Copeland, Micah Davison, Lorna Wilson

Location: Reno-Sparks CC Date: October 3, 2019 Time: 8:00 am - 5:00 pm