Otolith Microchemistry Analysis Research Articles

Life-history variation of two inland salmonids revealed through otolith microchemistry analysis

Increasingly, otolith microchemistry analysis is used as a tool to trace fish migrations, especially migrations of diadromous fishes. Yet, few studies have used otolith microchemistry to trace migrations in small inland watersheds, leaving major knowledge gaps in our understanding of inland fish spatial ecology. Here, we evaluate the use of tributary habitat for spawning and describe and compare fluvial brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) natal origin distribution, time spent in natal streams, and spawning site fidelity. 63% of rainbow trout and 57% of brown trout migrated after hatching. Brown trout showed greater variation in time spent in natal tributaries, suggesting that individuals are temporally distributing risk among offspring. By contrast, rainbow trout showed greater variation in natal origin, suggesting that individuals are spatially distributing risk among offspring. Our results indicate there is high inter- and intraspecific migration variation in inland salmonid populations, which may be linked to access to a mosaic of spawning and rearing habitat types.

Unravelinghabitat use of Coilia nasus from Qiantang River of China by otolith microchemistry

The habitat use and life history characteristics of the estuarine tapertail anchovy, Coilia nasus from Qiantang River were studied by examining the environmental signatures of Sr and Ca in otoliths using otolith microchemical analysis. The results indicate the C. nasus in the present study could be briefly divided into three types: Types 1/Type 2 of riverine origin and initial relative long-term/short-term freshwater residence, and Types 3 of estuarine origin and initial brackish early life history. The availability and fluctuation of certain levels of Sr:Ca ratios (i.e., Sr:Ca×1000) between salinity scale of 3.00 and 7.00 reveal that the C. nasus analyzed in this study spent much more time in brackish habitat of the river’s estuary. This study has established that the C. nasus of Qiantang River Estuary has a diverse and complex pattern of life history and habitat use which makes their life history and migration pattern vary from those of the Yangtze River.

Otolith microchemistry indicates regional phylopatry in the larval phase of an amphidromous fish (Gobiomorphus hubbsi)

ABSTRACTKnowledge of stock structure is key for the effective management of any fish species. Amphidromous fish, which live and spawn in freshwater but spend a pelagic larval period at sea, have typically been assumed to disperse widely during their larval phase, resulting in populations being sourced from a single unstructured larval pool. We used otolith microchemical analysis to examine the stock structure of bluegill bully (Gobiomorphus hubbsi), a declining amphidromous eleotrid endemic to New Zealand, along the west coast of South Island, New Zealand. Some drainages – even those in close proximity (c. 20 km) – were readily distinguishable based on otolith trace element concentrations, while little structure was evident between other geographically disparate locations. These results indicate that, at least in some cases, locally retained larvae, rather than a single unstructured larval pool, dominates recruitment. Management of bluegill bully and other amphidromous species must therefore consider the possibility of regionally distinct populations.

Investigation on shrimp feeding of <i>Coilia nasus</i> during its anadromous migration along the Yangtze River

刀鲚（Coilia nasus）是长江的名贵经济鱼类.虽然传统上认为其溯河生殖洄游全过程不会摄食，但该问题一直尚未完全弄清.作为有效解明这一问题的第一步，本研究在前期长江流域干流和湖泊刀鲚资源调查的基础上，先利用耳石微化学技术筛选出长江河口区、江苏江段、安徽江段和鄱阳湖水域溯河洄游型的刀鲚个体，再对其胃、肠容物的大型游泳动物（鱼、虾类）进行调查分析.结果发现，在河口区、江苏和安徽江段所有刀鲚个体胃充塞度为0级，均未发现摄食有游泳动物；而鄱阳湖水域刀鲚个体的胃充塞度达4~5级，均发现有摄食淡水虾类的日本沼虾（Macrobrachium nipponense）和秀丽白虾（Exopalaemon modestus）的情况.其中29%和71%的刀鲚胃中分别含有1只和2只虾.所有刀鲚个体肠内均未发现有内容物.鉴于鄱阳湖已被确定为溯河洄游型刀鲚的产卵场之一，结果表明长江刀鲚在经河口，通过长江江苏和安徽江段干流到达鄱阳湖产卵场的过程中应该不会摄食大型游泳动物；而进入鄱阳湖产卵场后会开始摄食日本沼虾和秀丽白虾.这种两阶段的现象可能反映出了刀鲚的一种在洄游通道上节约能量，以利长距离溯河；而在产卵场补充能量，以利于性腺最终成熟的生存策略.;Estuarine tapertail anchovy(Coilia nasus) is a valuable commercial fish in the Yangtze River. It is traditionally believed that C. nasus do not feed during their anadromous migration, but this issue is not yet fully clarified. As a pilot study on feeding of C. nasus during the whole process of anadromous migration, the present study investigated the nekton(e. g. shrimp, fish) in stomach and intestinal contents of C. nasus fish (confirmed as anadromous individuals by otolith microchemical analysis) previously collected in the Yangtze River's estuary, Chongming Island of Shanghai City, sections in Jiangsu and Anhui Provinces, and connected Lake Poyang in Jiangxi Province. The results showed that C. nasus from the river estuary and sections of Jiangsu and Anhui Provinces did not feed nekton and their stomach fullness indices were at 0 degree. In contrast, all C. nasus from Lake Poyang obviously fed nekton and their stomach fullness indices were at 4 to 5 degree. Furthermore, the nektons in stomach contents of the fish were all freshwater shrimps (Macrobrachium nipponense and Exopalaemon modestus), and one and two prawns were found in the stomach contents of 29% and 71% of the C. nasus fish, respectively. However, no nekton residual could be found in the intestinal contents of C. nasus studied. Since the Lake Poyang has been confirmed as a spawning site of anadromous C. nasus, the present study revealed a possible two-step-feeding process for the fish in the Yangtze River, namely, C. nasus may not feed (at least nekton) when moving upstream through the estuary and migratory channel in the sections of Jiangsu and Anhui Provinces, while they may start to feed shrimps of M. nipponense and E. modestus when entering the spawning site in the Lake Poyang. These phenomena may reflect a survival strategy of Yangtze C. nasus, i. e., the fish keeps fasting to save energy for its long distance anadromous movement, but starts to feed to supply energy for full gonad maturation and finish breeding.

Differences in the maturation level among life histories of the Japanese eel Anguilla japonica in the Nagata River, Japan

Abstract In order to understand the silver eel migration behavior of the Japanese eel Anguilla japonica, the life history of both the yellow stage (immature stage) and the silver stage (early maturing stage) was examined during the silver eel migration period, using otolith microchemical analysis of strontium (Sr) and calcium (Ca) concentrations. The mean Sr:Ca ratios in A. japonica from the elver mark to the otolith edge indicate eels of several general categories of migratory histories, including sea eels (average Sr:Ca ratios, ≥ 6.0 × 10-3), estuarine eels (average Sr:Ca ratios, 2.0 × 10-3 ≤ Sr:Ca < 6.0 × 10-3) and river eels (average Sr:Ca ratios, < 2.0 × 10-3), based on the criteria reported previously in A. japonica. A significant negative correlation was observed between the gonadosomatic index (GSI) and the mean Sr:Ca ratios during the growth phase after recruitment. Gonads of river eels were more developed compared to eels with other migratory histories. It thus appears that the maturation level for the silver eel migration to the open ocean varies depending on the life history.

Identifying the source population of fish re-colonizing an arid-land stream following wildfire-induced extirpation using otolith microchemistry

Movement is necessary for re-colonization of habitats following disturbance, but methods to estimate dispersal of small-bodied fishes are limited. We evaluated the efficacy of otolith microchemistry in identifying habitat origin of longfin dace Agosia chrysogaster in the Gila River, NM, USA. Additionally, we used this method to determine the source population of speckled dace Rhinichthys osculus that re-colonized a tributary reach following wildfire-induced extirpation. We determined otolith microchemical analysis was possible after finding elevated ambient water concentrations of Mg, Mn, and Sr in the disturbed tributary both before and after wildfire relative to other source streams. These water chemistry differences allowed us to test if speckled dace were derived from downstream populations, or from those potentially persisting within refugia in the fire-affected tributary. We found that otolith signatures consistently reflected water chemistry patterns for Mn and Sr, allowing us to classify individuals to known capture locations 86% (range = 74–100%) of the time. Otolith microchemistry techniques then revealed that 88% of speckled dace that re-colonized the fire-affected tributary reach were derived from refuge populations within the tributary. Our results indicated that otolith microchemistry could be an important tool for characterizing re-colonization dynamics of fish populations residing in chemically heterogeneous stream networks.

Lake and species specific patterns of non-diadromous recruitment in amphidromous fish: the importance of local recruitment and habitat requirements

Understanding migratory life histories is critical for the effective management and conservation of migratory species. However, amphidromous migrations (fish hatch in streams, immediately migrate to the sea for a feeding period and return to fresh water as juveniles) remain understudied owing to the difficulties of tracking tiny larval fish. Despite this, it has widely been assumed that amphidromous fish have open, resilient populations, with marine-rearing larvae dispersing widely during their pelagic phase. In the present study we tested the hypothesis that when an alternative freshwater pelagic habitat is available, non-diadromous recruitment will be the dominant process in sustaining amphidromous fish populations, with implications for their connectivity and resilience. Otolith microchemical analyses of five species (three Galaxias (Galaxiidae), two Gobiomorphus (Eleotridae)) from paired systems on the South Island of New Zealand indicated that when a suitable freshwater pelagic habitat existed downstream, non-diadromous recruitment was the primary population-sustaining process, typically contributing >90% of recruits. In addition, not all species recruited from all lakes, indicating the importance of the largely unstudied role of species-specific amphidromous larval requirements. The results of the present study emphasise the need to better understand the dynamics of individual populations of amphidromous fish, and highlight the importance of understanding species-specific early life history requirements to fully understand their distributions and management needs.

Using otolith microchemistry to differentiate between stocked and unstocked Australian bass (Percalates novemaculeata)

Understanding the contribution of stocking to fish populations is an essential part of any program to increase fish numbers and abundance. However, subsequent assessments that aim to quantify the success of fish stocking are rarely considered. Juvenile-sized (<200mm) Australian bass (Percalates novemaculeata), from the upper Snowy River, southern New South Wales (NSW), Australia (assumed to be stocked), wild mature-sized (>400mm) fish from estuarine areas of the Snowy River, juveniles (15–30mm) from a commercial Australian bass hatchery facility known to have supplied fish for past stockings in the Snowy River, and wild fish (>400mm) considered as controls from the Clarence River in northern NSW were used for otolith microchemical analysis. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to measure Sr:Ca and Ba:Ca ratios at the otolith core and across radial transects to verify natal origins of fish and more specifically, to confirm the origin of fish caught in the river that were assumed to have originated from a recent stocking program. Otolith core Sr:Ca ratios of juvenile fish collected from the upper Snowy River and hatchery fish were not significantly different suggesting they originated from the same source. Significant differences were found in core Sr:Ca and Ba:Ca between known origin hatchery fish and wild fish. Significantly higher Sr:Ca ratios were found at otolith cores compared to the edges in fish collected from the upper Snowy River, suggesting early life was spent in more saline conditions prior to stocking compared to wild fish. Otolith transect data showed a consistent decrease in Sr:Ca ratios and a simultaneous increase in Ba:Ca ratios at approximately 17–59mm from the core, corresponding with the size at which these fish were stocked. This study has demonstrated that otolith microchemistry can successfully distinguish stocked fish from wild recruits and reveals the timing of natural migrations or artificial translocations.

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.

Using Redd Attributes, Fry Density, and Otolith Microchemistry to Distinguish the Presence of Steelhead and Rainbow Trout in the Elwha River Dam Removal Project

AbstractThe removal of impassable dams can affect stream fish communities in many ways, including allowing previously separated anadromous and resident life history types to intermingle. Recolonization of steelheadOncorhynchus mykiss(anadromous Rainbow Trout) into areas that were previously occupied solely by resident conspecifics presents a challenge for monitoring because (1) staging or spawning adults may be difficult to directly observe; and (2) the offspring of the two life history forms are indistinguishable during early life. We evaluated the utility of using redd attributes, fry (age‐0) size, and fry density to distinguish the presence of steelhead and Rainbow Trout in the Elwha River, Washington. Redd area and substrate size differed between forms: steelhead redds were significantly larger and had a greater median substrate particle size than Rainbow Trout redds. Fry density was significantly higher in steelhead spawning reaches than in Rainbow Trout reaches during both survey years (2010 and 2011). Steelhead fry tended to be slightly larger than Rainbow Trout fry but not significantly so in either year. Additionally, otolith microchemical analyses indicated that all fry collected from newly colonized habitat were of steelhead maternal origin, and these fish were intermediate in size to the steelhead and Rainbow Trout fry collected prior to dam removal. Thus, fry size may not effectively differentiate parental origin despite the tendency of anadromous parents to be larger and to spawn earlier than residents. Redd attributes and fry density may be useful for evaluating the spatial distributions and relative abundances of steelhead and Rainbow Trout after dam removal. Our results have implications for other dam removal projects and other monitored species.Received April 13, 2015; accepted July 3, 2015

Beyond dichotomous life histories in partially migrating populations: cessation of anadromy in a long‐lived fish

Across animal taxa, migration allows individuals to exploit habitats and resources that predictably vary seasonally in suitability. Theory predicts that the "decision" to migrate or not is shaped by the relative fitness costs and benefits of exhibiting a given life history. Adoption of a migratory strategy is widely thought to reflect a dichotomous outcome; individuals are either resident or migratory, and continue to exhibit this life history until death. In fishes, anadromy and freshwater residency represents a well-studied life history dichotomy. Resident individuals may adopt a migratory life history later in life, but migratory individuals are not known to abandon this pattern. Here, we investigated the fitness benefits, as measured by body size, of residency and anadromy in a salmonid fish, Dolly Varden, Salvelinus malma, in Alaska, and reveal a novel life history: cessation of migration by older, larger individuals. Otolith microchemical analysis of Dolly Varden showed that while most fish migrated to sea at least once in their lives, lifelong resident fish exist in streams with close proximity to the ocean. Moreover, the probability of seaward migration in any year of life decreased annually after an individual's fourth year, and no fish migrated after their eighth year, while the oldest fish were captured in their 11th year. Migration conferred a size advantage in young fish, but the size benefits of marine foraging declined in older fish, at which time fish increasingly "retired from anadromy." Additionally, measurement of both natal otolith chemistry and the gonadosomatic index indicated a continued contribution to lifetime fitness, rather than senescence, in retired individuals. We suggest that the novel life history of reversion to residency by older fish is viable because foraging opportunities are subsidized by the predictable annual supply of energy-rich eggs and carcasses of spawning Pacific salmon.

Movement patterns of fish revealed by otolith microchemistry: a comparison of putative migratory and resident species

We examined movement patterns in two wide ranging species of freshwater fish, a putative resident species the slimy sculpin, Cottus cognatus, and a migratory species the Arctic grayling, Thymallus arcticus. We attempted to trace the extent and patterns of movement over the life history of individual fish using elemental signatures deposited in otoliths of fish that reflect distinctive freshwater chemistries. Patterns of movement were highly variable within both species of fish among the rivers examined. Patterns included movement among major river systems, use of smaller tributaries within a river, but also some individuals exhibited limited movement. Although the diversity of water chemistry signatures varied among watersheds, this was not reflected in a difference between the two species. There was a tendency for less variability in elemental signatures during the older life stages of the fish, particularly for sculpin. The life history information gained in this study demonstrates that both species make extensive movements within a watershed during their life history. Our otolith microchemistry analysis suggests excellent dispersal abilities, and reveals that, despite being referred to as migratory and resident, putative movements by many individuals from both species were extensive.

Diverse juvenile life‐history behaviours contribute to the spawning stock of an anadromous fish population

AbstractHabitat quality often varies substantially across space and time, producing a shifting mosaic of growth and mortality trade‐offs across watersheds. Traditional studies of juvenile habitat use have emphasised the evolution of single optimal strategies that maximise recruitment to adulthood and eventual fitness. However, linking the distribution of individual behaviours that contribute to recruitment at the population level has been elusive, particularly for highly fecund aquatic organisms. We examined juvenile habitat use within a population of sockeye salmon (Oncorhynchus nerka) that spawn in a watershed consisting of two interconnected lakes and a marine lagoon. Otolith microchemical analysis revealed that the productive headwater lake accounted for about half of juvenile growth for those individuals surviving to spawn in a single river in the upper watershed. However, 47% of adults had achieved more than half of their juvenile growth in the downstream less productive lake, and 3% of individuals migrated to the estuarine environment during their first summer and returned to freshwater to overwinter before migrating back to sea. These results describe a diversity of viable habitat‐use strategies by juvenile sockeye salmon that may buffer the population against poor conditions in any single rearing environment, reduce density‐dependent mortality and have implications for the designation of critical habitat for conservation purposes. A network of accessible alternative habitats providing trade‐offs in growth and survival may be important for long‐term viability of populations.

Evidence for an autumn downstream migration of Atlantic salmon Salmo salar (Linnaeus) and brown trout Salmo trutta (Linnaeus) parr to the Baltic Sea

In the eastern Baltic rivers, anadromous salmonid parr are known to smoltify and migrate to the sea from March until June, depending on latitude, climate and hydrological conditions. In this study, we present the first records of autumn descent of brown trout Salmo trutta and Atlantic salmon Salmo salar from the Baltic Sea Basin. Otolith microchemistry analyses revealed that these individuals hatched in freshwater and had migrated to the brackish water shortly prior to capture. The fish were collected in 2006, 2008, 2009 and 2013 from Eru Bay (surface salinity 4.5–6.5 ‰), Gulf of Finland. This relatively wide temporal range of observations indicates that the autumn descent of anadromous salmonids is not a random event. These results imply that autumn descent needs more consideration in the context of the effective stock management, assessment and restoration of Baltic salmonid populations and their habitats.

Suitability of otolith microchemistry for stock separation of Baltic cod

Microchemical otolith analyses have been shown to provide valuable information on the life history, dispersal and stock characteristics of teleost fish. In the present study, the suitability of this technique for identifying the origin and distribution of Atlantic cod Gadus morhua L. from the Baltic Sea was examined using laser ablation-ICPMS. The capacity to distinguish individuals from different Baltic Sea stocks and from the adjacent North Sea stock based on incoporation of stock-specific elemental fingerprints along otolith growth axes was investigated. It was further tested if different origins led to spawning-site specific element concentrations in otolith cores. The results indicate that microchemical analyses of Baltic cod otoliths are applicable for differentiating individuals of different stocks. Analyses of similarities including 12 element/calcium ratios resulted in significant differences between individuals from the eastern and the western Baltic Sea and between North Sea and Baltic Sea samples. Sr/Ca, Ba/Ca, Y/Ca, Mg/Ca, Zr/Ca and Mn/Ca ratios had the strongest discriminatory power. A further separation of individuals caught in 3 different spawning grounds of the eastern Baltic, however, was not possible. Elemental compositions from the core regions of otoliths from young of the year cod caught in eastern and western Baltic Sea spawning grounds showed significant differences in Sr/Ca, Ba/Ca and Mg/Ca concentrations. Analyses of similarities again showed significant differences between these areas for juveniles. This study demonstrates the potential of otolith microchemical analyses to provide important information about the stock structure and connectivity of G. morhua in the Baltic Sea.

Anadromous Migrants of Shirauo, Salangichthys microdon, in Lake Ogawara, as Determined by Otolith Microchemistry Analysis

Anadromous Migrants of Shirauo, Salangichthys microdon, in Lake Ogawara, as Determined by Otolith Microchemistry Analysis

Bayesian hierarchical mixture models for otolith microchemistry analysis

The field of fisheries research commonly uses classical statistical classification methods to estimate the proportion of fish that return to natal spawning grounds to spawn. With the advent of otolith microchemical analysis, researchers are able to extract information from fish ear stones (otoliths) about the chemical composition of water in which fish have spent distinct periods of their lives. Here we present a method of analysis set in the Bayesian statistical paradigm which enables explicit incorporation of habitat information into the analysis. The ecological system is seen as arising from a mixture of disparate fish populations and information from the biological relationships inherent in otolith formation is exploited through the hierarchical model structure. We present the model and motivation, demonstrate the validity of the model through simulation studies, and conclude with an analysis of a data set from Lake Erie.

Influence of host habitat on the occurrence of gill monogeneans Pseudodactylogyrus spp. on wild Japanese eels Anguilla japonica

With technological improvements in otolith microchemical analysis, the flexible use of habitat from coastal marine to fresh waters has been discovered in Japanese eels Anguilla japonica. We examined the occurrence of 3 congeneric gill monogeneans-Pseudodactylogyrus anguillae, P. bini, and P. kamegaii-on wild Japanese eels, in relation to the host's flexibility. From April 2008 to October 2009, 114 eels were collected from a brackish-water cove and 2 rivers flowing into the cove in Ehime Prefecture, western Japan. Based on otolith microchemical analysis, the eels were discriminated according to the following 4 types of habitat use: freshwater residents (Type I), individuals utilizing low-salinity habitats (Type II), downstream habitat-shifters (Type III), and cove residents (Type IV). P. anguillae occurred mainly on Type I and II eels, while P. bini was primarily found on Type I eels. In contrast, P. kamegaii occurred mainly on Type III and IV eels. Thus, we conclude that species composition and infection levels of Pseudodactylogyrus spp. clearly differed with habitat-use patterns of Japanese eels. Also, since P. anguillae was scarcely found on either Type III or IV eels, this study suggests that previous identifications of monogeneans collected from European brackish-water localities as P. anguillae may require verification.

Newcomers in the Baltic Sea: an attempt to trace the origins and whereabouts of thicklip grey mullet Chelon labrosus

In recent years, thicklip grey mullet Chelon labrosus has shown increasing expansion of its native habitats in the north-eastern Atlantic into northerly adjacent areas including the North Sea and the brackish Baltic Sea. Despite the regular annual and seasonal occurrence of C. labrosus in the western Baltic during the warm months, nothing is known of the origin or whereabouts of the mullet during the cold season. As different possible migration scenarios can be considered, we performed otolith microchemistry analyses on specimens from the western Baltic Sea to identify the origin of this nonindigenous species. Comparison with North Sea samples revealed common habitat preferences and underlined the highly euryhaline nature of C. labrosus in different recently occupied habitats. Occasional fluctuations of Sr/Ca ratio along the growth axis suggest periodical migration between waters of different salinities but did not reveal distinct migration pathways.

Segregation of SE Pacific and SW Atlantic southern blue whiting stocks: integrating evidence from complementary otolith microchemistry and parasite assemblage approaches

Southern blue whiting Micromesistius australis support one of the largest industrial fisheries in South America. Two main spawning/nursery grounds are known: one in the SW Atlantic Ocean (SWA), southwest from the Falkland (Malvinas) Islands; and other in the SE Pacific Ocean (SEP), south from the Taitao Peninsula. Juveniles originating from both grounds are believed to mix during migration and/or in feeding areas in the Scotia Sea. Previous efforts to distinguish stocks in this area have yielded contradictory results between genetics and otolith microchemical analyses. In the present work we revisited the null hypothesis of a single stock occurring in the broader SWA-SEP region by comparing and integrating results from different approaches: trace metals (Ca, Sr, Ba, Mg, Mn) and stable isotopes (δ13C, δ18O) in otolith cores, and parasite assemblage compositions in adults from SWA and SEP spawning grounds. We found significant differences in Sr:Ca, δ13C and δ18O mean ratios between spawning grounds. The best trace element discriminant model classified 83% of the samples. Each stable isotope discriminated >90% of the samples, while combining them into a bivariate discriminant model led to 100% classification success. Higher δ18O levels in the SWA samples agreed with lower mean temperature and higher ambient δ18O levels in that area. Parasite assemblage compositions also showed significant differences between grounds regarding the prevalence of Chondracanthus, Contracaecum, Hepatoxylon and Grillotia and the abundance of Diclidophora, Anisakis, Contracaecum, Hysterothylacium and Hepatoxylon. Parasite-based discriminant models supported 90–100% correct assignment of samples to capture location. Although preliminary due to limited sampling coverage, our results support the existence of at least two ecologically distinct sub-populations of southern blue whiting in South America. The joint use of otolith microchemistry and parasitological techniques showed to be a promising way to test hypotheses concerning ecological stocks in marine fishes.