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Hard‐part microchemistry offers a powerful tool for inferring the environmental history and stock assignment of individual fishes. However, despite the applicability of this technique to a wide range of fisheries conservation and management issues, its use has been restricted to only a small fraction of North American species and inland waters. In this article, we provide freshwater fisheries professionals with an accessible review of methods and applications of hard‐part microchemistry techniques. Our objectives are to (1) summarize the science of hard‐part microchemistry; (2) provide guidelines for designing hard‐part microchemistry studies, including sample sizes, laboratory analyses, statistical techniques, and inferential limitations; and (3) identify conservation and management applications where these techniques may be particularly useful. We argue that strategic use of hard‐part microchemistry methods (specifically when they are used in concert with other indirect tracer techniques such as stable isotope chemistry and genetics) can advance fish management and conservation across all stages of fish life history.

SUMMARY The swimming abilities of fishes are of vital importance to their ecology,and studies on fish swimming have been the focus of research for over a century. Here we explore the relationship between swimming ability and external body morphology, using data on Ucrit swimming speeds of 100 species of pre-settlement juvenile coral reef fishes (at the transition between the larval and adult habitats), comprising 26 different families from 5 orders. The taxonomic diversity of this methodologically consistent dataset provides a unique opportunity to examine the relationship between form and function in fish swimming across a broad taxonomic range. Overall, we found that a predictive model incorporating total length(TL), the square of caudal peduncle depth factor(CPDF2) and aspect ratio (AR) can be used to accurately predict swimming performance of a wide range of fish families, and was able to explain 69% of the variability in swimming performance of these pre-settlement juvenile fishes. The model was also able to successfully predict the swimming speed of an out-group salmonid species (Oncorhynchus mykiss). There was no evidence that the model fit differed among taxonomic groups, despite the inclusion of five different orders of fishes,suggesting that body morphology sufficiently explains the bulk of differences in swimming performance. Furthermore, the model appears to work equally well for fishes from the Great Barrier Reef and the Caribbean, and for families with different adult habitat associations and swimming modes. It remains to be determined how well the model predicts the swimming abilities of temperate species as well as adults of these same species. This model provides an invaluable means of predicting swimming abilities of pre-settlement juvenile fishes that are unable to be reared in the laboratory, do not perform well in swimming flumes or are unable to be captured live in the field.

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Amphidromous fishes are important members of oceanic island freshwater communities. Although often depauperate, amphidromous fish assemblages on islands are largely composed of endemic species. Little is known about the effects of anthropogenic stressors on amphidromous fishes, and the consequences of climate-driven changes in water quality and quantity are particularly uncertain. Focusing on native fishes in Hawaii, we discuss the potential for climate change to intensify 3 major threats facing amphidromous fish: (1) loss of 'ridge-to-reef' migratory corridors via disruption of surface water connectivity, (2) in-stream habitat degradation and (3) exotic species introductions. Successfully addressing these and other threats to native fish in Hawaii will require approaches that balance conservation needs with use of water resources. Conservation initiatives should focus on 'scaling up' ongoing projects intended to demonstrate how stream protection and restoration, non-native species removal and reintroductions can benefit at-risk species. Research initiatives should focus on determining the ecological controls on recruitment under current and future climate conditions. KEY WORDS: Amphidromy · Climate change · Freshwater fishes · Hawaii · Ocean−stream connectivity Resale or republication not permitted without written consent of the publisher Contribution to the Theme Section 'Endangered river fish: threats and conservation options'

Summary Co‐introductions of non‐native parasites with non‐native hosts can be a major driver of disease emergence in native species, but the conditions that promote the establishment and spread of non‐native parasites remain poorly understood. Here, we characterise the infection of a native host species by a non‐native parasite relative to the distribution and density of the original non‐native host species and a suite of organismal and environmental factors that have been associated with parasitism, but not commonly considered within a single system. We examined the native Hawaiian goby Awaous stamineus across 23 catchments on five islands for infection by the non‐native nematode parasite Camallanus cotti. We used model selection to test whether parasite infection was associated with the genetic diversity, size and population density of native hosts, the distribution and density of non‐native hosts, land use and water quality. We found that the distribution of non‐native C. cotti parasites has become decoupled from the non‐native hosts that were primary vectors of introduction to the Hawaiian Islands. Although no single intrinsic or extrinsic factor was identified that best explains parasitism of A. stamineus by C. cotti, native host size, population density and water quality were consistently identified as influencing parasite intensity and prevalence. The introduction of non‐native species can indirectly influence native species through infection of co‐introduced parasites. Here, we show that the effects of ‘enemy addition’ can extend beyond the range of non‐native hosts through the independent spread of non‐native parasites. This suggests that control of non‐native hosts is not sufficient to halt the spread of introduced parasites. Designing importation regulations to prevent host–parasite co‐introductions can promote native species conservation, even in remote areas that may not seem susceptible to human influence.

Tropical cyclones drive coastal ecosystem dynamics, and their frequency, intensity, and spatial distribution are predicted to shift with climate change. Patterns of resistance and resilience were synthesized for 4138 ecosystem time series from n = 26 storms occurring between 1985 and 2018 in the Northern Hemisphere to predict how coastal ecosystems will respond to future disturbance regimes. Data were grouped by ecosystems (fresh water, salt water, terrestrial, and wetland) and response categories (biogeochemistry, hydrography, mobile biota, sedentary fauna, and vascular plants). We observed a repeated pattern of trade-offs between resistance and resilience across analyses. These patterns are likely the outcomes of evolutionary adaptation, they conform to disturbance theories, and they indicate that consistent rules may govern ecosystem susceptibility to tropical cyclones.

We assessed the prevalence of life history variation across four of the five native amphidromous Hawai'ian gobioids to determine whether some or all exhibit evidence of partial migration. Analysis of otolith Sr.: Ca concentrations affirmed that all are amphidromous and revealed evidence of partial migration in three of the four species. We found that 25% of Lentipes concolor (n = 8), 40% of Eleotris sandwicensis (n = 20) and 29% of Stenogobius hawaiiensis (n = 24) did not exhibit a migratory lifehistory. In contrast, all individuals of Sicyopterus stimpsoni (n = 55) included in the study went to sea as larvae. Lentipes concolor exhibited the shortest mean larval duration (LD) at 87 days, successively followed by E. sandwicensis (mean LD = 102 days), S. hawaiiensis (mean LD = 114 days) and S. stimpsoni (mean LD = 120 days). These findings offer a fresh perspective on migratory life histories that can help improve efforts to conserve and protect all of these and other at-risk amphidromous species that are subject to escalating anthropogenic pressures in both freshwater and marine environments.