ICES Journal of Marine Science: Journal du Conseil

Morales-Nin, Beatriz; Geffen, Audrey J.

doi: 10.1093/icesjms/fsv150pmid: N/A

AbstractFish otoliths have provided biologists with a treasure-house of valuable life history information across levels of biological organization from individuals to ecosystems. Otoliths have long been used to provide the age and growth estimates which are basic data that underpin scientific fisheries and fisheries ecology. The traditional use of calcified tissues (CS) has been augmented by new applications to address questions of population connectivity, migration, and trophic ecology. These tools have become increasingly important in meeting the demands for spatially explicit and ecosystem-level management tools. Analysis of CS is now extended to applications related to spatial use (essential habitats) and as a record of past and present environmental conditions. This special volume of the ICES Journal of Marine Science contains contributions from the 5th International Otolith Symposium (IOS 2014), an ICES Science Symposium held in October 2014, in Mallorca, Spain. IOS 2014 is a continuation of a series of symposia that started in 1993 to encourage the exchange of information and expertise and to promote the development of new techniques and applications for otolith-based analysis in ecology, management, and conservation. IOS 2014 was the largest meeting to date, with 329 participants from 45 countries. The aim of IOS 2014 was to explore the use of CS as tools to support management and define indicators at environmental, community, population, and individual levels. This international forum is the centre for the exchange of information about developments in the field. New techniques of analysis, statistical treatment, and indeed new areas of application are all presented in this forum. Regular attendees are often the prominent users of otolith analyses in their home institution, and many are active in ICES work. This is also a premier venue for interaction between ICES scientists and those working in other parts of the world. North America, Japan, Taiwan, and Australia are particularly active in advancing otolith techniques, and exchange of ideas and information is crucial to improving the science in the ICES community.

Díaz-Gil, Carlos; Palmer, Miquel; Catalán, Ignacio A.; Alós, Josep; Fuiman, Lee A.; García, Elena; Gil, María del Mar; Grau, Amalia; Kang, Andrew; Maneja, Rommel H.; Mohan, John A.; Morro, Bernat; Schaffler, Jason J.; Buttay, Lucie; Riera-Batle, Inmaculada;

Harbitz, Alf; Albert, Ole Thomas

doi: 10.1093/icesjms/fsv048pmid: N/A

AbstractThis paper focuses on artefacts that may corrupt stock discrimination by shape analysis of otolith contours, how one can examine if such artefacts are important, and how they can be avoided. The scope focuses on Fourier transforms of contour points, the linear Fisher discrimination technique, and success rates based on cross validation by the “leave one out at a time” technique. The “zero-score” technique is introduced as a tool to examine the importance of a possible artefact, based on the theoretical result that the probability of correct classification of any otolith from either of two identical groups is zero. If one of the identical groups is exposed to a possible influential factor, e.g. a different smoothing, a high classification rate will reveal that this factor is an important artefact. The concept of a “lasso contour” is introduced that drastically reduces the impact of smoothing and provides a non-concave shape that enables a one-dimensional representation of the contour without ambiguities. Results are illustrated by comparison between Greenland halibut (Reinhardtius hippoglossoides) otolith contours from southern Greenland and Northeast Arctic waters. The conclusion is that the probability of correct classification of locality based on the original contours is too optimistic (77–79%), while the scores based on lasso contours are insensitive to smoothing and still optimistically high (68–70%).

Williams, Ashley J.; Newman, Stephen J.; Wakefield, Corey B.; Bunel, Melanie; Halafihi, Tuikolongahau; Kaltavara, Jeremie; Nicol, Simon J.

doi: 10.1093/icesjms/fsv042pmid: N/A

AbstractDeepwater snappers (Family Lutjanidae) are important to artisanal and subsistence fisheries in Pacific Island countries. Most species of deepwater snapper are considered vulnerable to exploitation due to their extended longevity and low natural mortality rates. However, the sustainability of deepwater snapper fisheries in Pacific Island countries remains uncertain because there are limited resources available to collect the required data for comprehensive stock assessments. Reliable estimates of the age composition for exploited deepwater snapper populations are limited primarily because of the lack of skills and resources required for routine age estimation from sectioned otoliths. The development of alternative low-cost approaches to derive estimates of age for deepwater snappers is required. We evaluated the performance of using otolith morphometrics (weight, length, width, and thickness) to obtain estimates of age for the most important target species in these fisheries: Etelis carbunculus, E. marshi, E. coruscans, and Pristipomoides filamentosus. We compared age compositions and fishing mortality rates (F) derived from otolith morphometrics with those derived from counts of annual increments in otoliths. We then used the ratio of F to natural mortality (M) as a biological indicator to evaluate the potential effects on management responses by comparing estimates of F/M derived from otolith morphometrics with those derived from annual increment counts. Age compositions and estimates of F and F/M did not differ significantly between those derived from otolith morphometrics and those derived from annual increment counts for all species. These results demonstrate that management responses would likely be similar whether based on age estimates derived from sectioned otoliths, or predicted from otolith morphometrics. In the absence of sufficient resources to section otoliths for age estimation, we recommend that otolith morphometrics be used as a proxy for age in assessments of deepwater snapper fisheries in Pacific Island countries, and potentially for other similar data-limited fisheries.

Padilla, Andrew J.; Brown, Randy J.; Wooller, Matthew J.

doi: 10.1093/icesjms/fsv096pmid: N/A

AbstractA commercial fishery targeting the anadromous Bering cisco (Coregonus laurettae) is occurring in the Yukon River, Alaska, USA. All three of the known global spawning populations occur in Alaska. Managers believed that two of the three populations were being harvested in the fishery. To determine the likelihood of a mixed-stock fishery, we used 87Sr/86Sr values from the freshwater region of otoliths, from spawning adult Bering cisco of known origin (n = 82), to create a baseline. A 10-fold cross-validated, quadratic discriminant function analysis (DFA) of the three baseline population 87Sr/86Sr values (Yukon River, n = 27; South Fork Kuskokwim River [Kuskokwim River], n = 25; and Susitna River, n = 30) correctly reclassified 98.8% of the fish analysed. The baseline DFA model was then used to classify the 87Sr/86Sr values from a set of otoliths removed from commercially harvested Bering cisco (n = 139). Using a posterior probability threshold of 90%, we found that >97% of the commercial samples were classified as originating in the Yukon River. The remainder of the commercial samples were classified as originating in the Kuskokwim River (0.7%) or from the Susitna River (1.5%). The presence of 87Sr/86Sr values consistent with the Susitna River discovered in the Yukon River baseline (n = 1) and commercial samples (n = 2) suggested either multiple isotope signatures within the Yukon River population or straying among populations. Strontium isotope data provide an effective tool to monitor the movements and stock composition of Bering cisco.

Wells, R. J. David; Kinney, Michael J.; Kohin, Suzanne; Dewar, Heidi; Rooker, Jay R.; Snodgrass, Owyn E.

doi: 10.1093/icesjms/fsv051pmid: N/A

AbstractChemical signatures in otoliths and muscle tissue of albacore (Thunnus alalunga) from two regions of the North Pacific were characterized to examine population structure. Regions included northern (offshore northwest United States and Canada, >40°N) and southern (offshore southwest United States and Mexico, <40°N) areas where albacore have demonstrated region-specific differences in movement and size at age. Juvenile (ages 1–4 years) albacore were collected from each region through recreational and commercial fisheries over a 5-year period (2009–2013). Three different otolith chemistry assays were performed, including whole otoliths (proxy for lifetime signature), otolith edge (recent signature), and otolith core (nursery signature). Whole otolith δ13C and δ18O showed similar δ13C and enriched δ18O (∼0.5‰) values for juvenile albacore collected in the southern region; classification success to the two regions ranged from 78 to 91% during each year (similar age classes). Otolith edge δ13C and δ18O showed similar results as whole otoliths, but no regional differences were found for otolith core chemistry. Incorporation of trace element concentrations from whole otoliths improved discrimination between regions to 90–100% classification success during each year of the study, with significantly higher Ba:Ca, Mg:Ca, and Mn:Ca in albacore otoliths from the northern region. Albacore from the southern region also displayed enriched muscle δ13C (∼1.21‰) and δ15N (∼0.85‰) values relative to fish of the same size range from the northern region. Discrimination success between the two regions across all years using muscle δ13C and δ15N was 91%. Ultimately, results from this study suggest regional separation of albacore in the eastern North Pacific warranting region-specific vital rates in future modelling efforts.

Baumann, Hannes; Wells, R. J. D.; Rooker, Jay R.; Zhang, Saijin; Baumann, Zofia; Madigan, Daniel J.; Dewar, Heidi; Snodgrass, Owyn E.; Fisher, Nicholas S.

doi: 10.1093/icesjms/fsv062pmid: N/A

AbstractJuvenile Pacific bluefin tuna (PBT, Thunnus orientalis) are known to migrate from western Pacific spawning grounds to their eastern Pacific nursery and feeding grounds in the California Current Large Marine Ecosystem (CCLME), but the timing, durations, and fraction of the population that makes these migrations need to be better understood for improved management. To complement recent work focused on stable isotope and radiotracer approaches (“tracer toolbox”; Madigan et al., 2014) we explored the suitability of combining longitudinal analyses of otolith microstructure and trace elemental composition in age ∼1–2 PBT (n = 24, 66–76 cm curved fork length) for inferring the arrival of individuals in the CCLME. Element:Ca ratios in transverse otolith sections (9–12 rows, triplicate ablations from primordium to edge, ø50 μm) were quantified for eight elements: Li, Mg, Mn, Co, Cu, Zn, Sr, and Ba, which was followed by microstructure analysis to provide age estimates corresponding to each ablation spot. Age estimates from otoliths ranged from 328 to 498 d post-hatch. The combined elemental signatures of four elements (Ba, Mg, Co, Cu) showed a significant increase at the otolith edge in approximately half of the individuals (30–60 d before catch). Given the different oceanographic properties of oligotrophic open Pacific vs. high nutrient, upwelling CCLME waters, this signal is consistent with the entry of the fish into the CCLME, which was estimated to occur primarily in July after a transoceanic migration of ∼1.5–2.0 months. Our approach comprises a useful addition to the available tracer toolbox and can provide additional and complementary understanding of trans-Pacific migration patterns in PBT.

Minke-Martin, Vanessa; Brian Dempson, J.; Sheehan, Timothy F.; Power, Michael

doi: 10.1093/icesjms/fsv033pmid: N/A

AbstractOtolith-derived estimates of mean marine temperatures used by West Greenland 1SW Atlantic salmon (Salmo salar) of North American origin were determined for fish collected in 2009 and 2010. Otolith material corresponding to the second summer at sea was subsampled, via micro-milling, and analysed by mass spectrometry to produce stable oxygen isotope (δ18O) values from which temperature use estimates were obtained from a salmonid-based fractionation equation. Mean temperature estimates did not differ significantly by period (early vs. late summer), or capture year. The mean and variation estimates were also consistent with temperature use values previously published in the literature or derived from the limited number of data storage tags that have been retrieved for Atlantic salmon, with 80% of all individuals occupying temperatures in the 3.9–9.7°C range. Among-individual differences in temperature use did not correlate with measured otolith growth zone widths. Given the temporal, spatial and methodological variation associated with the derivation of marine temperature use estimates for Atlantic salmon, the data were interpreted to define a range of preferred temperatures within which among-individual differences in growth were driven by the interaction of feeding and temperature use, possibly as a result of the opportunistic feeding behaviour known to predominate among Atlantic salmon.

McBride, Richard S.

doi: 10.1093/icesjms/fsv047pmid: N/A

AbstractIn a typical age and growth study, multiple estimates of individual fish age are generated: by readers, methods, etc. These samples of paired data are evaluated with three complementary approaches: (i) tabulate or graph the data to illustrate patterns, (ii) calculate indices of precision to evaluate repeatability, and more recently, (iii) use tests of symmetry to evaluate bias. Herein, I simulated age data to evaluate the diagnostic power of these different approaches in terms of four types of accuracy: (i) no bias between known and estimated age, (ii) bias by adding 1 year to the estimated age, (iii) bias by subtracting 10% from the estimated age, and (iv) both biases together. Precision of estimated ages (standard deviation = 5, 10, and 15% of known age) was varied for each type of bias. Age-bias plots had difficulty detecting bias in ages classes with few (e.g. ≤5) individuals sampled. A Bland–Altman-bubble plot is introduced as an alternative to age-bias plots. In these simulations, the various indices of precision were either not diagnostic (i.e. per cent agreement) or redundant (average per cent error could be predicted from Chang's coefficient of variation). Evans and Hoenig's test and Bowker's test of symmetry performed well in most simulations, but each has specific weaknesses. Bowker's test was superior by having marginally fewer type I error rates; however, it had much worse type II error rates. McNemar's test offered no additional interpretative power in these simulations. All tests of symmetry had difficulty diagnosing bias when precision was low. These simulated results support continued use of all three approaches because they are complementary. Additional simulations would be helpful to confirm that these guidelines are relevant in other representative cases.