Explore the vast range of titles available.

To secure traceability along supply chains of foodstuffs, the spatiotemporal variability of trace elements’ fingerprints (TEF) in fish otoliths provides a powerful tool to determine and discriminate the origin. Spatiotemporal variability of TEF was examined in a commercially important seafood, Japanese eel (Anguilla japonica), by means of laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS). Six elemental ratios (Na:Ca, Mg:Ca, P:Ca, K:Ca, Sr:Ca, and Ba:Ca) were determined in the otoliths of specimens originating from four aquaculture farms to examine the spatial variability and from one wild habitat over three years to examine the temporal variation. Significant temporal variation was found in Mg:Ca and Sr:Ca ratios; however, discriminant function analysis showed a lower temporal variation (50%) for the three years. Spatial variations were significant in Sr:Ca and Ba:Ca ratios, and discriminant function analysis showed high (80%) spatial variation among the four farms. Otolith TEF in the Japanese eel showed specific spatial variation among aquaculture farms but intangible temporal variation, suggesting the otolith TEF reflect each aquaculture environment. The present study shows that otolith TEF can be a reliable tool to discriminate the geographic origin of the Japanese eel.

Most studies that infer geographic distributions of fish using otolith microchemistry assume that environmental factors (e.g. temperature, salinity) outweigh intrinsic effects (e.g. size, condition); however, this assumption has not been rigorously tested, particularly in marine fish. Here, we report the results of a long-term experimental study of European plaice Pleuronectes platessa L. and explore relationships between blood plasma and ambient water chemistry over a 12 mo reproductive cycle. Overall, blood plasma was found to be highly regulated, with few elements exhibiting strong, if any, correlation with ambient concentrations. This sets a first order limit on the sensitivity of otolith chemistry to fluctuations in ambient seawater chemistry. The observed temporal, ontogenetic and sex-specific variations in blood plasma elemental concentrations indicated significant physiological influences on elemental uptake and processing mechanisms. Physiological variables exerted relatively strong influences on the uptake and regulation of the softer, more thiophilic elements (Mn, Cu, Zn, Se and Pb), as well as Sr and Ca. By contrast, seasonal and sex-related variations were relatively minor among the hard acid metal ions (Li⁺, Mg2⁺, K⁺, Rb⁺, Ba2+). Overall, plasma elemental concentrations covaried most strongly and consistently with plasma protein concentrations. For this exclusively marine species, seasonal changes in physiology governed intra-annual variations in blood chemistry and, by implication, also regulate ion availability to the otolith. Based on these observations, we recommend that sex and age should be controlled for in future experimental designs using otolith microchemistry to infer stock structure or migration patterns.

Otolith morphological and microchemical analyses are relatively new scientific research methods used in fish stock evaluation and management. However, in Tunisia, only morphological methods have been used. The objective of this study was the Sarpa salpa stock discrimination of Djerba and Kerkennah by the otoliths morphological and microchemical analysis, while carrying out a fluctuating asymmetry analysis and a stock comparison of males and females for each population. The results revealed significant differences between the Djerba and Kerkennah populations, significant differences between the stocks of males and females in each population, and a highly significant fluctuating asymmetry for both populations. The results of the otolith morphological analysis were similar to those of the microchemical analysis. This result proves that both morphological and microchemical analyses are powerful tools for fish stock discrimination.

Black Carp (Mylopharyngodon piceus) was imported to the USA to control aquaculture pond snails. This species has escaped captivity and occurs in parts of the Mississippi River, several tributaries, and floodplain lakes, which is concerning due to potential competition with native fishes and predation on native mussels, many of which are imperiled. However, Black Carp captures have primarily been incidental by commercial fishers, and evidence of reproduction in the wild is limited. The objectives of this study were to assess relative abundance of aquaculture-origin and wild Black Carp using ploidy and otolith stable isotope analysis, identify spatial extent of natural reproduction using otolith microchemistry, assess age distributions of wild and aquaculture-source Black Carp to infer years in which natural reproduction occurred and timing of aquaculture escapement or introductions, and estimate size and age at maturation to assess whether recruitment to adulthood has occurred. Results revealed that Black Carp are established in parts of the Mississippi River basin based on findings that: (1) non-captive Black Carp primarily consist of fertile, naturally-reproduced fish, (2) reproduction has occurred in several rivers, (3) multiple year classes of wild fish are present, and (4) wild fish have recruited to adulthood. Multiple introductions or escapements of aquaculture-source fish into the wild, including both fertile and functionally sterile individuals, were also inferred. Individual growth appears to be rapid, although considerable variation was observed among fish. Additional study is suggested to refine understanding of where and when Black Carp reproduction is occurring in the Mississippi River basin.

Yellowstone cutthroat trout inhabiting Yellowstone Lake have declined substantially over the past 25 years as a result of predation by invasive lake trout, the presence of whirling disease, and periods of persistent drought. We used otolith microchemistry to assess whether cutthroat trout recruitment patterns have changed in response to these environmental stressors. Though water chemistry variation among the 22 sampled spawning tributaries was low, we identified 9 distinct spawning stream clusters. Random forest models were developed for assessing relative recruitment, yielding a high classification accuracy of 84.4% for known-origin cutthroat trout fry otoliths and 79.0% for simulated otolith signatures based on water chemistry. Proportion of recruitment varied significantly between pre- and post-stressor samples (X 2  = 15.40, P  = 0.03). The majority of pre- (0.84) and post-stressor (0.77) recruitment occurred in the same three stream clusters, but there was a notable decrease in recruitment in streams with high whirling disease prevalence, and a notable increase from the tributary cluster without whirling disease and with low lake trout predation risk. Conservation efforts should be focused on protecting important spawning tributaries and improving cutthroat trout recruitment in spawning streams that in the past likely contributed much greater numbers of fish.

Otoliths are calcified structures and the information contained within their chemistry or shape can be used to infer life history events, migration patterns, and stock structure of a fish population. Understanding how otolith chemistry is affected by temperature, salinity, interactive effects of abiotic factors, ontogeny, physiology, etc. is essential for the reconstruction of the environment that affected the fish. Otolith shape is also affected by environmental conditions in addition to the genotype. The applications of otolith chemistry and shape for stock discrimination have increased in recent years because of the advancements in analytical methods and the related software. The stock identification methods sometimes provide variable results but if we use complementary approach the information generated could be more reliable which can be used to prepare effective management and conservation strategies. It appears warranted to generate more information on the factors influencing otolith chemistry and shape especially when two or more factors exert synergetic influence. Therefore, the objectives of this review paper were to provide comprehensive information on various factors influencing the otolith chemistry and shape, and the utility of otolith chemistry and shape for fish stock discrimination with an emphasis towards the research areas needing additional studies.

Yellowfin tuna Thunnus albacares is a highly exploited species in the Indian Ocean. Yet, its stock structure is still not well understood, hindering assessment of the stock at a suitable spatial scale for management. Here, young-of-the-year (<4 mo) yellowfin tuna otoliths were collected in 2018 and 2019, from 4 major nursery areas in the Indian Ocean: Madagascar, Seychelles-Somalia, Maldives and Sumatra. First, direct age estimates were made in a subset of otoliths by visually counting microincrements to identify the portion of the otolith corresponding to the larval stage. We then developed 2-dimensional maps of trace element concentrations to examine spatial distribution of elements across otolith transverse sections. Different distribution patterns were observed among the elements analysed; Li, Sr and Ba were enriched in the portion of the otolith representing early life, whereas Mn and Mg concentrations were heterogeneous across growth bands. Last, we analysed inter-annual and regional variation in otolith chemical composition using both trace elements (Li, Mg, Sr, Ba and Mn) and stable isotopes (δ13C and δ18O). Significant regional variation in otolith chemical signatures was detected among nurseries, except between Madagascar and Seychelles-Somalia. Otolith δ13C and δ18O were important drivers of differentiation between western (Madagascar and Seychelles-Somalia), Maldives and Sumatra nurseries, whereas the elemental signatures were cohort specific. Overall nursery assignment accuracies were 69−71%. The present study demonstrates that baseline chemical signatures in the otoliths of yellowfin tuna are regionally distinct and can be used as a natural tag to investigate the nursery origin of older individuals in the Indian Ocean.

Dams on rivers are known to facilitate the colonisation and spread of aquatic alien and native invasive species, but the actual mechanisms involved are poorly understood. Since the construction of the Solina Dam on the upper San River system in Poland, European perch (Perca fluviatilis) have expanded their distribution into the headwaters of this river system, becoming a native invader. In this study, we assessed the spread of perch in detail over time upstream of the Solina Reservoir, and used otolith trace element microchemistry to determine the spawning and larval rearing locations of perch in the catchment upstream of the dam. Extensive sampling over several years across the catchment upstream of the Solina Reservoir confirmed the widespread occurrence of perch into the headwaters of the tributary river systems, with smaller size classes dominating locations closer to the Solina Reservoir. Despite perch being widely distributed upstream of the Solina Reservoir, otolith microchemical analysis indicated the populations from various reservoir tributaries mostly shared the same spawning and larval rearing habitat, most likely the Solina Reservoir. Our results suggest that reservoirs can facilitate the colonisation of river systems by providing a critical habitat element that would be otherwise missing from riverine landscapes, i.e., an extensive and productive pelagic larval rearing environment. This research shows that the impacts of large dams can extend many kilometers upstream from the river reaches directly affected by the resulting impoundment.

Nonindigenous lake trout (Salvelinus namaycush) expansion in Yellowstone Lake has led to a large decline in the native Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) population. We assessed whether otolith microchemistry could be used to identify subbasin natal origins and long-term use by lake trout as a potential tool for optimizing removal efforts. 87Sr:86Sr and Sr:Ca ratios in otolith cores were used to assess natal origins and 87Sr:86Sr ratios in otolith transects were used to assess movement patterns. Water chemistry was similar throughout the lake, ranging from 0.70634 to 0.70642 and 3.94 to 4.38 mmol/mol for 87Sr:86Sr and Sr:Ca ratios, respectively. Lake trout otoliths also showed little variation in 87Sr:86Sr and Sr:Ca ratios of the natal region and 87Sr:86Sr across otolith transects. Thus, we found that microchemical differences among Sr isotope and Sr:Ca elemental ratios in otoliths were insufficient to detect the natal origin or extensive within-lake movement that has been established from telemetry investigations. Detailed analysis of other elements or isotopes in hard-part microchemistry, in combination with other tools for detecting movement, may improve detection of natal origin and life history movement among fishes within freshwater lentic systems.

Yellow Perch (Perca flavescens) inhabit both nearshore and coastal wetland habitats of the Laurentian Great Lakes throughout their lifetime and are known to exhibit different movement life histories. However, uncertainty persists in the spatial extent of this variation and in the duration of habitat use. To explore these uncertainties, we used a multi-metric approach that included water and otolith microchemistry and tissue stable isotope ratios (δ13C, δ15N). The ratio of manganese to calcium in otoliths was used to identify transitional movements between nearshore Lake Ontario and wetland habitats while carbon and nitrogen tissue isotope ratios revealed variable duration of wetland inhabitance. Our research suggests that the multi-metric approach was useful for addressing questions that could not be answered by one method alone. Our results demonstrate individual differences in duration of coastal wetland habitat residence among Yellow Perch, which may influence their susceptibility to recreational harvest. As Yellow Perch are an important species of consideration for management agencies such as the Great Lakes Fishery Commission, exposing such diversity is important when considering the potential for differential contributions of individuals with variable movement life histories to overall population stability and resilience over time.