Validating estuarine movements from otoliths for an imperiled fish

BackgroundCaptive breeding programs are one of the many tools used by conservation practitioners as a means of conserving, supporting, and supplementing populations of imperilled species. Captive breeding programs exist around the globe for freshwater mussels and fishes, but the availability of evidence exploring the effectiveness of these programs has not yet been explored using systematic map criteria. This systematic map aims to identify, collate and describe the evidence that exists on the effectiveness of captive breeding programs, for the purpose of achieving conservation targets for imperilled freshwater fishes and mussels in the wild. The outputs of this systematic map will help to inform conservation managers and policy makers who are responsible for protecting imperilled freshwater species by identifying existing information and highlighting key information gaps for captive breeding programs operating in temperate regions.MethodsThis systematic map will search for, compile, and map existing literature on the effectiveness of captive breeding programs for the conservation of imperilled freshwater fishes and mussels. The systematic map will search using five bibliographic databases, two public search engines, and 19 specialist websites and will include both primary and grey literature. All studies that discuss details related to captive breeding programs for the conservation of imperilled freshwater fishes and/or mussels in temperate regions will be included in the map. The systematic map will produce a narrative report describing the evidence, including knowledge gaps evidence clusters, and a MS-Excel searchable database of articles and extracted metadata.

Underwater observation is a widely used fish-sampling method, but capture efficiencies of this method are often unknown. For accuracy, survey counts require correction by measuring capture efficiencies of sampling protocols. Capture efficiencies for underwater observation were calculated for three small imperiled fishes—Etheostoma sitikuense (Citico Darter), Noturus flavipinnis (Yellowfin Madtom), and Noturus baileyi (Smoky Madtom)—using modified mark-recapture methods. Fishes were tagged with visual implant elastomer tags, released at sites within Abrams Creek in the Great Smoky Mountains National Park, and then recaptured. Efficiencies were calculated by comparing numbers of released individuals to recaptures. In the propagation facility, tag retention was 100 percent, and no post-tagging mortality was observed. Capture efficiency (CE = 0.12) was low for all species and potentially influenced by predation upon marked fish, emigration of fish from sites, or difficulty in sampling some habitats. Thus, population sizes may be larger than observed due to low capture efficiencies. Our results highlight challenges to estimating capture efficiencies for imperiled fishes when using underwater observational methods.

There is an extensive literature establishing, validating, and quantifying a wide range of responses of fishes to fasting. Our study complements this work by comparing fed and unfed treatments of hatchery-raised Delta Smelt (Hypomesus transpacificus)—an imperiled fish that is endemic to the San Francisco Estuary and its tributaries in California, USA—across a diverse suite of endpoints over a two-month time series. The experiment was conducted at 15.9°C, and individuals were sampled at 12 time points as starvation became increasingly severe. We found that hepatosomatic index and condition factor were relatively sensitive to starvation, becoming significantly depressed at Day 4 and 7, respectively. Histological analysis of liver showed elevated cytoplasmic inclusion bodies at Day 7, followed by increased glycogen depletion, single cell necrosis, and hydropic vacuolar degeneration at Day 14, 21, and 28, respectively. Of four antioxidants measured, glutathione decreased at Day 4, superoxide dismutase increased at Day 14, catalase increased at Day 56, and glutathione peroxidase was not affected by starvation. The net result was a ~2-fold increase in lipid peroxidation (malondialdehyde) in fasted fish that was highly inconsistent through time. RNA to DNA ratio and triglycerides in muscle were relatively insensitive to starvation, only consistently decreasing with fasting after mortality began increasing in the ‘No Feeding’ treatment, at Day 21. Together, these results suggest that Delta Smelt mobilize hepatic energy stores far more rapidly than lipids in muscle when subjected to fasting, leading to rapid atrophy of liver and the development of cytoplasmic inclusion bodies—possibly autophagosomes—in hepatocytes.

Wild at heart: Programs to diminish negative ecological and evolutionary effects of conservation hatcheries

– The ashy darter, Etheostoma cinereum, is an imperiled fish within the Cumberland and Tennessee drainages of the southeast United States. An understanding of habitat associations and the relationship of habitat use across multiple spatial scales are critical elements in its conservation. Our objectives were to quantify habitat associations at the stream reach and microhabitat scales for adult and juvenile darters, and to understand the linkage between the two scales based on gradients of habitat use. We focused our efforts within the Rockcastle River, Kentucky (Cumberland River drainage), because the watershed was known to contain a relatively large ashy darter population. Three hundred twenty‐two individuals were collected from 21 reaches. The species was restricted to the mainstem of the river and the lower reaches of the larger tributaries. The distribution and abundance of adult and juvenile darters differed significantly at each spatial scale, and both groups demonstrated non‐random use of the available habitat. Gradients of stream size and substrate size were identified as important factors. A threshold of environmental quality was determined based on the habitat use patterns among the two scales. Habitat use between the two scales was independent within the threshold, indicating that the specific quality of the microhabitats did not necessarily matter within a stream reach. However, beyond the threshold, a decrease of at least 48% in adult and juvenile darter abundance was seen, indicating that a sufficient network of suitable microhabitats is needed to support a good population of darters within a stream reach.

Metal pollution from mining is a threat to lotic fishes, although legislation that requires improved water quality and provides funding for remediation has been enacted to combat this stressor. The Spring River in southeastern Kansas historically received inputs of cadmium, copper, lead, and zinc that reduced the prevalence of several sensitive and imperiled fishes. Long-term reductions in these toxic metals have occurred since the 1990's because of management activities, but presently it is unknown how riffle fish communities responded to improved water quality. As such, the objective of our research was to quantify changes in riffle fish community structure between 1993-1995 and 2019-2021 using a before-after-control-impact (BACI) study design. Responses were quantified with univariate analyses to examine the interactive effects of time period (i.e., historical versus contemporary), pollution tolerance classification (i.e., intolerant, moderately-intolerant, moderately-tolerant, and tolerant), and site position (i.e., above versus below the most severe historical metal pollution inputs) on relative abundance, occupancy, and species richness of riffle fishes. We used multivariate analyses to examine temporal changes in community structure above and below pollution inputs. Our findings indicated that intolerant fish species relative abundance increased between the historical and contemporary time periods throughout the Spring River. Occupancy of all fishes increased over time in the formerly metal contaminated portion of the Spring River, becoming similar to values in the reference reach. Changes in species richness depended on site position and pollution tolerance, as temporal increases of intolerant and moderately intolerant species richness were most pronounced in the lower Spring River below historical metal pollution inputs. Multivariate analyses revealed a significant interaction between time period and site position, as there was a shift in community structure over time in the lower reach that was less pronounced in the upper reach. Most of the intolerant species that increased in prevalence are of high conservation priority, thus our research suggested that legislation enacted to improve water quality produced a ripple effect that stimulated the recovery of imperiled fish species.

The construction of dams on large rivers has negative impacts on native species. Environmental flows have been proposed as a tool to mitigate these impacts, but in order for these strategies to be effective they must account for disparate temperature and flow needs of different species. We applied a multi‐objective approach to identify trade‐offs in dam release discharge and temperature for imperiled fishes with contrasting habitat requirements, while simultaneously meeting the needs of human water users. Using the Sacramento River (California, USA) as a case study, our model suggests that current management aimed at providing high discharge for downstream water users and cold water for endangered winter‐run Chinook salmon (Oncorhynchus tshawytscha) has detrimental impacts on threatened green sturgeon (Acipenser medirostris), which require warm water for juvenile growth. We developed an optimal dam release scenario that can be used to meet the needs of salmon, sturgeon and human water users. Our results show that dam releases can be managed to successfully achieve these multiple objectives in all but the most severe drought years. Synthesis and applications. This study shows that managing dam releases to meet the needs of a single species can have detrimental effects on other native species with different flow and temperature requirements. We applied a multi‐objective approach to balance environmental requirements of multiple species with the needs of human water users. Our findings can be used to guide management of Shasta Dam and our approach can be applied to achieve multi‐object management goals in other impounded rivers.

Efficacy of depletion models for estimating abundance of endangered fishes in streams

<em>Abstract</em>—Habitat restoration in streams is critical to recovery of imperiled fishes. In the Pacific Northwest of North America, stream habitat restoration has focused primarily on anadromous salmonids <em>Oncorhynchus </em>spp. listed under the Endangered Species Act. Substantial restoration efforts have focused on the Oregon Coast evolutionary significant unit of Coho Salmon <em>O. kisutch</em>. However, many of these efforts have been local in scale (i.e., particular reaches within relatively small streams, high up in watersheds) and do not address habitat-forming processes at the watershed scale. Other anadromous species such as Chum Salmon <em>O. keta </em>and Pacific Lamprey <em>Entosphenus tridentatus </em>that co-occur in these watersheds are rarely targeted in habitat restoration yet are thought to benefit from restoration efforts for Coho Salmon. However, Chum Salmon and Pacific Lamprey tend to occur lower in watersheds than Coho Salmon, inhabit freshwater for different periods of time, and are therefore challenged by different limiting factors. As a result, benefits from restoration efforts for Coho Salmon may not be fully realized by Chum Salmon and Pacific Lamprey. Mounting evidence suggests that process-based restoration may yield substantial biological dividends for anadromous fishes. Although process-based restoration is still an area of active research, it does possess a stronger and more holistic conceptual foundation than restoration strategies aimed at creating particular channel forms. Process-based restoration addresses the geological, physical, chemical, climatic, and ecological processes that interact to form habitat mosaics to which anadromous fishes have adapted. Understanding and working within these processes throughout entire watersheds and downstream into the estuary has the potential to benefit multiple anadromous fishes and substantially improve the ecological functions of watersheds. We explore the range of habitat relationships expressed among three imperiled anadromous fishes—Coho Salmon, Chum Salmon, and Pacific Lamprey—and present case studies to illustrate the importance of implementing process-based restoration to address limiting factors in their freshwater habitats. We conclude by suggesting three main strategies to address restoration challenges and limitations: forming multidisciplinary collaborations of restoration practitioners, investing in education and outreach to build larger and more diverse constituencies, and developing spatial and organizational tools to expand restoration efforts to the watershed scale.

Phenotype management: a new approach to habitat restoration

Recent collections of the Asian fish tapeworm Bothriocephalus acheilognathi in the Rio Grande have raised concern about the potential impacts on Rio Grande endemic and imperiled fishes. The objectives of this study were to determine distribution and definitive hosts of the Asian fish tapeworm within the Rio Grande drainage and to quantify occurrences and abundances. In total, 1,992 fish spanning 11 families were collected and examined for Asian fish tapeworms in the Rio Grande and the Pecos and Devils rivers. The parasite was collected from red shiners Cyprinella lutrensis, Tamaulipas shiners Notropis braytoni, sand shiners N. stramineus, river carpsuckers Carpiodes carpio, plains killifish Fundulus zebrinus, western mosquitofish Gambusia affinis, blue suckers Cycleptus elongatus, blacktail shiners Cyprinella venusta, proserpine shiners Cyprinella proserpina, and Manantial roundnose minnow Dionda argentosa, with the latter four species being new host records. Monthly collections of red shiners from Big Bend National Park exhibited prevalence levels above 15% in January-March and December and below 10% during April-June and October. With over 50% of the Rio Grande icthyofauna in Texas considered imperiled, the occurrence and pathological effects of the Asian fish tapeworm in combination with reduced water quantity and quality and increased habitat fragmentation are of concern for these taxa.

Freshwater ecosystems are among the most threatened environments on our planet. Disturbances across the terrestrial landscape accrue within freshwater ecosystems and, combined with global stressors such as climate change and invasive species, create a complex situation for recovering imperilled fishes. Given the drastic global decline of freshwater fishes, similarly extreme efforts are needed for their conservation and recovery — repatriation represents one such opportunity. Species repatriation describes the act of releasing a species in areas where extirpation has occurred. Paradoxically, a long history of fish introductions for recreational purposes exists, yet examples of repatriation for imperilled fishes are relatively rare compared with terrestrial species. Stemming from the restoration and species introduction literature, we identify five ecological themes to consider when evaluating repatriation potential of freshwater fishes and suggest that repatriation represents the “drastic” approach needed to achieve meaningful conservation milestones.

Life-history variation is the raw material of adaptation, and understanding its genetic and environmental underpinnings is key to designing effective conservation strategies. We used large-scale genetic pedigree reconstruction of anadromous steelhead trout (Oncorhynchus mykiss) from the Russian River, CA, USA, to elucidate sex-specific patterns of life-history traits and their heritability. SNP data from adults returning from sea over a 14-year period were used to identify 13,474 parent-offspring trios. These pedigrees were used to determine age structure, size distributions and family sizes for these fish, as well as to estimate the heritability of two key life-history traits, spawn date and age at maturity (first reproduction). Spawn date was highly heritable (h2 = 0.73) and had a cross-sex genetic correlation near unity. We provide the first estimate of heritability for age at maturity in ocean-going fish from this species and found it to be highly heritable (h2 from 0.29 to 0.62, depending on sex and method), with a much lower genetic correlation across sexes. We also evaluated genotypes at a migration-associated inversion polymorphism and found sex-specific correlations with age at maturity. The significant heritability of these two key reproductive traits in these imperiled fish, and their patterns of inheritance in the two sexes, is consistent with predictions of both natural and sexually antagonistic selection (sexes experience opposing selection pressures). This emphasizes the importance of anthropogenic factors, including hatchery practices and ecosystem modifications, in shaping the fitness of this species, thus providing important guidance for management and conservation efforts.

What is an endangered species worth? Threshold costs for protecting imperilled fishes in Canada

Stream drying, especially in the western United States, is becoming more common as the climate warms and precipitation patterns become less predictable; consequently, fisheries managers need to prioritize conservation efforts where water (and fish) will persist in the future. Yellow Creek in the upper Bear River watershed (Utah and Wyoming) contains one of the largest remaining populations of Northern Leatherside Chub Lepidomeda copei, an imperiled fish. Lower reaches are drying during summer months, partly due to water withdrawals, thus reducing Northern Leatherside Chub populations and relegating the remaining fish to isolated pools until the water returns. This study used an unmanned aerial vehicle to capture high-resolution and spatially explicit imagery over 19 km of Yellow Creek in a few weeks during late August when the water is the most limiting to the fish. Through imagery and subsequent GIS analysis, we identified 405 previously unknown potential refuge-pool habitats for Northern Leatherside Chub and determined their location, size, and spatial distribution, thereby helping managers prioritize stream reaches for native fish conservation and restoration. While the cost of unmanned aerial vehicle flights was estimated to be 2.5 times that of on-the-ground surveys in 2016, unmanned aerial vehicle technology continues to become more cost effective and, unlike traditional surveys, provides high-resolution and spatially referenced data.