Live Bait Research Articles

Engaging bait retailers as part of the live bait pathway: bait retailer characteristics and aquatic invasive species prevention

In the Great Plains region, the live bait industry relies on approved species of cultured and wild-harvested baitfish. The release of baitfish by anglers is prohibited in most locations, but angler compliance with these regulations can be low. Bait retailers can increase compliance with regulations by communicating with anglers about aquatic invasive species (AIS) risk and through their business practices. We conducted 66 telephone surveys with bait retailers in southeastern South Dakota from June to July 2023 to (1) characterize bait retailer practices that may influence AIS risk and (2) determine the extent and willingness of bait retailers to display educational materials to reduce AIS risk. Fathead minnows (Pimephales promelas) were the most sold species (96% of respondents), and most bait came from wholesale retailers (74%). However, 24% of bait retailers also occasionally bought from local bait harvesters. Non-advertised species were observed at least once in shipments by 35% of bait retailers, but retailers only encountered species they did not intend to order in 1% of their inspections. Regular inspections for non-advertised species in baitfish shipments were conducted by 74% of retailers. Most inspections occurred at the time of receiving a baitfish shipment (36%) or daily (36%). Bait retailers were interested in displaying provided AIS educational materials (80%), including posters and pamphlets (59%), stickers (41%), bait bags (39%), and keychains/boat key floats (36%). Displaying educational materials at bait retail locations may increase angler knowledge of AIS and compliance with bait disposal regulations.

Unclear host taxonomy hinders parasite studies: An up-to-date checklist of the protozoan and metazoan parasites of Phoxinus minnows (Teleostei: Leuciscidae).

Phoxinus minnows are small freshwater fish found throughout Eurasia. The taxonomy of this genus is still under investigation, and new species are regularly described. They are frequently introduced outside their native range due to their use as live bait for angling, and such fish introductions can have diverse impacts on the recipient areas. Before the rise in interest regarding the diversity of this genus in the past 15 years, studies carried out on their biology and ecology reported their findings for the Eurasian minnow Phoxinus phoxinus Linnaeus, 1758, which was then considered ubiquitous. A parasites checklist for Phoxinus minnows has yet to be published, and the recent progress on the taxonomy of this genus has enabled us to propose a reassignment of parasite records to their proper host. The most thoroughly studied potential species were the North European species Phoxinus sp. 7 sensu Palandačić et al. 2017, Phoxinus isetensis, and P. phoxinus. We were able to highlight a gap in knowledge for numerous species that have received little-to-no attention in terms of parasitology. Systematic molecular identification of Phoxinus minnows should be conducted when studying their parasites, as a reliable identification of the host is vital in parasitology research. Future research will certainly reveal a species-specific composition of the parasitofauna occurring in Phoxinus, especially among widespread parasites such as Gyrodactylus and Diplostomum. Such specificities could even become tools for assessing the introduction routes of Phoxinus species.

Angler knowledge of live bait regulations and invasive species: insights for invasive species prevention

The prevention of aquatic invasive species is one of the most cost-effective management strategies for reducing negative ecological, economic, and social impacts to freshwater ecosystems. The release of leftover baitfish via the live bait trade has been identified as a high-risk pathway for introducing invasive species beyond physical barriers (e.g., mountains, dams). To assess differences in behavior surrounding live bait use and angler knowledge of invasive species, we conducted in-person angler surveys at waterbody access sites (i.e. boat ramps with available shore fishing and a shore fishing location with no boat ramp) along the Missouri River, above and below Gavins Point Dam (Yankton, South Dakota, USA). We were primarily interested in whether angler behavior and knowledge differed among fishing locations over the course of a year because of potential variation in risk. Gavins Point Dam is impervious to fish passage and prevents the spread of invasive silver carp Hypophthalmichthys molitrix and bighead carp H. nobilis (collectively known as bigheaded carp), but bigheaded carp could be transported above this dam by the use of live baitfish. Regardless of where respondents fished (above the dam/carp absent, below the dam/carp present, or both), 70% ± 11.12 of anglers used live baitfish and 57% ± 3.14 participated in ‘higher risk’ baitfish practices including release. Knowledge of bigheaded carp was limited, as only 2% ± 1.31 of respondents identified both bigheaded carp as invasive in an image collage, 51.82% ± 4.48 could not identify where invasive carp are present/absent, and 40% ± 3.34 of anglers had not received any information regarding bigheaded carp. These findings highlight limitations in angler knowledge, compliance, and identification of native and invasive species. Future implementable actions could include invasive species and baitfish release outreach via electronic media sources or additional signage that address these knowledge gaps.

Combined Use of Fatty Acid Profiles and Elemental Fingerprints to Trace the Geographic Origin of Live Baits for Sports Fishing: The Solitary Tube Worm (Diopatra neapolitana, Annelida, Onuphidae) as a Case Study.

Diopatra neapolitana Delle Chiaje, 1841 (Annelida, Onuphidae) is one of the most exploited polychaete species in European waters, particularly in Ria de Aveiro, a coastal lagoon in mainland Portugal, where the overexploitation of this resource has led to a generalized decline of local populations. In an attempt to reduce the impact of harvesting, several management actions were implemented, but illegal poaching still fuels a parallel economy that threatens the sustainable use of this marine resource. The present study evaluated the combination of fatty acid profiles and elemental fingerprints of the whole body and jaws, respectively, of D. neapolitana collected from four harvesting locations within Ria de Aveiro in order to determine if their geographic origin could be correctly assigned post-harvesting. Results showed that both fatty acid profiles and elemental fingerprints differ significantly among locations, discriminating the geographic origin with higher accuracy when combining these two natural barcodes than when employing each individually. The present work can, therefore, contribute to the implementation of an effective management plan for the sustainable use of this marine resource, making it possible to detect if D. neapolitana was sourced from no-take zones and if it was collected from the place of origin claimed by live bait traders.

Multiple introduction pathways of non-native Phoxinus minnows (Teleostei: Leuciscidae) in Corsica revealed by its hidden diversity and their parasites

The introduction of freshwater fish species is a leading cause of aquatic biodiversity erosion and can spread parasites to native populations. Hidden diversity evidenced by recent taxonomic revisions can add further complexity to the issue by rendering biological assessment data incomplete. The Eurasian minnows Phoxinus are one such example of cryptic diversity, with several described species being invasive. Current non-native fish populations in the small Mediterranean island of Corsica (France) are the result of successive waves of introductions, including several Phoxinus species. This study aims at determining which Phoxinus species were introduced to Corsica using the cytochrome oxidase subunit I barcoding marker, reconstructing their introduction routes and examining their parasite communities. The study found four species in Corsica: Phoxinus phoxinus and Phoxinus csikii mainly in the northernmost studied drainage basin and Phoxinus dragarum and Phoxinus septimaniae in the Tavignano drainage basin. P. phoxinus and P. csikii were most likely introduced through a live bait wholesaler while P. dragarum and P. septimaniae were probably introduced by recreational anglers bringing their bait from continental France. The molecular study of their Gyrodactylus (Platyhelminthes: Monogenea) parasites with the ITS marker allowed us to hypothesize inter-drainage basin secondary introduction routes for P. phoxinus and P. dragarum. In several sampling sites, Phoxinus minnows had black spot disease caused by encysted metacercariae of Digenea, likely Posthodiplostomum cuticola. These parasites were also found on the brown trout Salmo trutta in a locality where this patrimonial species co-occurs with Phoxinus minnows. Barcoding should be used in fish communities monitoring to help to accurately identify cryptic species.

The Effect of Short-Term Artificial Feed Domestication on the Expression of Oxidative-Stress-Related Genes and Antioxidant Capacity in the Liver and Gill Tissues of Mandarin Fish (Siniperca chuatsi).

To investigate whether Mandarin fish developed oxidative stress after being domesticated with artificial feed, we conducted a series of experiments. Oxidative stress is an important factor leading to diseases and aging in the body. The liver integrates functions such as digestion, metabolism, detoxification, coagulation, and immune regulation, while the gills are important respiratory organs that are sensitive to changes in the water environment. Therefore, we used the liver and gills of Mandarin fish as research materials. The aim of this study was to investigate the effects of short-term artificial feed domestication on the expression of oxidative stress genes and the changes in oxidative-stress-related enzyme activity in the liver and gills of Mandarin fish. We divided the Mandarin fish into two groups for treatment. The control group was fed with live bait continuously for 14 days, while the experimental group was fed with half artificial feed and half live bait from 0 to 7 days (T-7 d), followed by solely artificial feed from 7 to 14 days (T-14 d). The experimental results showed that there was no difference in the body weight, length, and standard growth rate of the Mandarin fish between the two groups of treatments; after two treatments, there were differences in the expression of genes related to oxidative stress in the gills (keap1, kappa, gsta, gstt1, gstk1, SOD, and CAT) and in the liver (GPx, keap1, kappa, gsta, gstt1, gr, and SOD). In the liver, GPx activity and the content of MDA were significantly upregulated after 7 days of domestication, while in the gills, SOD activity was significantly upregulated after 7 days of domestication and GPx activity was significantly downregulated after 14 days of domestication. These results suggest that artificial feed domestication is associated with oxidative stress. Moreover, these results provide experimental basic data for increasing the production of aquaculture feed for Mandarin fish.

Ant communities and their trophobionts shape the incidence of pests and diseases in Indonesia’s coffee agroforestry system

Abstract. Muhammad FN, Rizali A, Rahardjo BT. 2024. Ant communities and their trophobionts shape the incidence of pests and diseases in Indonesia’s coffee agroforestry system. Biodiversitas 25: 1127-1134. Ants play various roles in a coffee agroecosystem, and their presence may impact biological control in coffee plantations. Despite the pantropical economic importance of coffee, most research is focused on the Americas. This study investigates how ant communities and their trophobionts shape the incidences of pests and diseases in the Indonesian shade coffee agroecosystem. Three 30 m x 30 m plots consisting of a total of 256 coffee plants were observed from January to March 2022. Ant communities and their trophobiont were observed using three methods: visual, tuna bait, and live bait. The ants found were classified into dominant and non-dominant based on their nesting behavior and dominance in the bait trap. Pest damage and disease intensity observation were also conducted three times. Generalized linear models were used to test the relationships between ant, hemipteran, coffee berry borer, twig borer damage and leaf rust disease intensity. Twenty-one species of ants were found, and five of them were categorized as dominant ants. Ants correlate coffee pest damage and disease intensity, their hemipteran trophobionts, or both. Dolichoderus thoracicus ant positively correlated with all trophobiont hemipteran and negatively correlated with twig borer damage. Technomyrmex albipes positively correlated with aphids but negatively with flatids. Meanwhile, Tetraponera sp.1 ant only positively correlated with flatids. In trophobiont hemipteran group, all except aphids positively correlated with coffee pests and disease. Scale insect Coccus viridis positively correlated with coffee leaf rust and twig borer infestation intensity, while flatid presence even positively correlated with all coffee plant pest and disease intensity. Indirectly, ants may reduce coffee pests and diseases through hemipteran suppression. The results suggest that the interaction of ants and their trophobiont hemipteran can act as a biological control agent for coffee pests and diseases.

“Completely Free”: How a Subsumption of Labour and Nature Framework Explains the Surprising Expressions of “Freedom” by Immigrant Worm pickers in Ontario

AbstractCanadian nightcrawler (Lumbricus terrestris) worms, the most popular live bait for recreational freshwater anglers, are hand‐picked from Ontario dairy farmers’ fields by an immigrant labour force working in the middle of the night with limited equipment. Though no picker enjoys the arduous activity of picking worms, they do express feelings of “freedom” and “autonomy” in the job. Such expressions are surprising coming from mostly non‐English‐speaking immigrants, labouring with bent backs under dreary conditions producing profit for their employers in an unregulated industry. To understand these counterintuitive conceptions of freedom, I connect debates around “un/free labour” and “constrained agency” with the Marxist concepts of formal and real subsumption of labour and nature to reveal how the ecological conditions of commodity production shape capitalist control over labour. I argue worm‐picker agency should be understood by seeing how the subsumption of labour is related to the subsumption of nature.

Live‐bait industry as a pathway for movement of nonnative and invasive species: Implications for conservation of native Texas fishes

AbstractObjectiveLive‐bait species are widely used in recreational fishing throughout the United States. However, the use of invasive fish species as live bait has been identified as a common pathway for their introduction into aquatic ecosystems. We assessed the role that the live‐bait industry has in facilitating the introduction of nonnative and invasive species into Texas rivers. We focused on two invasive cyprinodontid species, the Sheepshead Minnow Cyprinodon variegatus and Gulf Killifish Fundulus grandis, which are believed to have been introduced into inland Texas rivers via bait‐bucket releases by anglers.MethodsWe conducted telephone and in‐person surveys of live‐bait shops in Texas on a seasonal basis (summer, fall, winter, spring) for 1 year. Locally owned bait shops and regional aquaculture facilities and hatcheries were included in the surveys.ResultSurveys did not reveal the presence of these invasive cyprinodontids in inland bait shops but did reveal the sale of nonnative Goldfish Carassius auratus and their black color morph, the black salty goldfish. Surveys conducted among inland and coastal live bait shops confirmed the sale of only one nonnative bait fish and six bait items native only to certain regions of Texas. Telephone surveys with aquaculture industry experts revealed that the aquaculture industry was also facilitating the movement of nonnative game and nongame fish species throughout the state.ConclusionGiven the potential for nonnative and invasive species to negatively affect recipient aquatic ecosystems, the continued distribution of such species within the aquaculture industry represents a potential threat in Texas. Our findings highlight the need for close monitoring of the live‐bait industry in the state to prevent further introductions into inland waters and reduce potential ecological risks to native fish populations and overall ecosystem functions and services.

Hidden diversity within Beauveria and Metarhizium – Comparing morphology, barcoding, multilocus phylogenies and whole-genome sequences

Accurately identifying entomopathogenic fungi is crucially important, but the current approach of analysing four genes might not provide sufficient resolution. In this study, we investigated the different resolution provided by multilocus phylogenies and approaches based on whole genome sequence data. Fungi were isolated from soil samples that were collected from five different vegetation types (dry sclerophyll forest, agricultural grassland, rainforest, suburban parkland, and sugar cane fields) and across four different suburban soil habitat types in southeast Queensland. Three different agricultural pests were used as live baits, cotton stainer bug, diamondback moth, and rust-red flour beetle. Whole-genome sequencing was conducted for all 83 isolates recovered, and the ITS2 region was extracted from the genome assemblies to make initial species identifications with the UNITE database. We also extracted tef1a 3′, tef1a 5’, rpb1 and rpb2 genes from the Metarhizium genomes and the bloc, tef1a and rpb1 genes from Beauveria genomes to construct multilocus phylogenies and obtain species identification. To investigate the genetic relationships across 14 isolates of Beauveria bassiana and (independently) across 43 isolates of Metarhizium based on whole-genome data, we genotyped single nucleotide polymorphism (SNP) markers and conducted principal components analysis on the whole-genome SNP data. The multilocus methods identified isolates to species more precisely than ITS2, except in the one unresolved clade in the Metarhizium phylogeny. The whole-genome approach identified more genetic clusters than the multilocus phylogenies identified species among the isolates, and the morphological results correlated with some of the genetic clusters, so they likely represent distinct species not detected by the other methods. The genetic clusters were not associated with vegetation type or bait insect species. This is the first comparison of the resolution of multilocus phylogenetics with that of whole-genome SNP data for these genera. We suggest how the genetic clusters identified here may be investigated further to determine whether they represent unrecognised species within these groups.

Opportunities for regional collaboration and prevention: Assessing the risk of the live bait trade as a pathway of invasive species

Anthropogenic introductions of invasive species via various trade and transport pathways have resulted in significant threats to native biodiversity, ecological services, and conservation programs. The live bait trade represents one anthropogenic pathway in which varying preventative actions may deter the introduction of aquatic invasive species. In this study, we collected 259 environmental DNA (eDNA) samples from 112 unique live bait retailers across the central United States to detect two high-priority invasive species in the ecologically and economically important Great Plains region. Additionally, we collected information on risk factors that may influence positive eDNA detections (presence of non-advertised fish species, presence of educational signage, and distance from established, high-priority, invasive populations) to evaluate current risk and preventative actions surrounding the live bait trade pathway. Out of the 100 initially assessed bait shops, 10 % tested positive for at least one invasive target species, 12 % had non-advertised species present within purchased baitfish, and 13 % displayed educational signage regarding invasive species. From a subset of repeated and new bait retailers, 11 % and 17 % tested positive, respectfully, and none had educational signage. We also found that bait retailers closer to recorded invasive species observations had a higher probability of having a positive eDNA detection, indicating that education and outreach should target invasion fronts. Our work highlights the opportunity and need for broad-scale approaches for regulations, education and outreach, and surveillance programs. Such collaborations are needed to evaluate inconsistencies in preventative actions among regions, successfully manage pathways of invasive species introductions, and better conserve natural resources.

Revealing the role of crab as bait in octopus fishery: An ecological and fishing approach to support management decisions

In southern Portugal, artisanal octopus fisheries play an important socioeconomic role. Live crab bait in traps was used up to 2010 and banned in 2012. Such regulation, based on co-management advice, was not established under a scientific fundament. As a result, a long-standing controversy ensued with some fishing associations claiming that live crab bait increased fishing effort and exploitation rates and therefore risked the octopus stock status, while other fishers denied all these alleged impacts. The issue has not been resolved so far due to lack of scientific studies. In this study, we resolve the controversy conducting experimental fishing to determine by-catch and octopus catch rates using live crab bait versus other types of baits based on fish and assess the stock status of octopus over-time with constant parameters (hypothesis of no effect of the use of live crab bait) versus time-varying parameters (hypothesis of raised exploitation rates and riskier stock status). Bycatch was very low regardless of bait type. Our experimental fishing trials showed that fish-based baits increase bycatch and octopus catch rates. Stock assessment models showed that exploitation rates and stock status do not worsen in years of use of crab bait. We conclude that the use of crab bait in octopus fishery does not lead to increased exploitation rate or risks for stock sustainability status. Other considerations involving fishing costs and fishing operations further highlight the advantages of lifting the ban on the use of live crab bait in the Algarve octopus fishery.

Present Status and Future Developmental Perspectives of Pole and Line Fishery in Sri Lanka

Present Status and Future Developmental Perspectives of Pole and Line Fishery in Sri Lanka

Mitochondrial phylogeny of fusilier fishes (family Caesionidae) from the Laccadive archipelago reveals a new species and two new records from the Central Indian Ocean.

Fusiliers of the family Caesionidae comprise a group of Indo-Pacific reef fishes important in the live bait and artisanal fisheries in many parts of its range, particularly in the Indian Ocean region. Using newly generated mitochondrial COI sequences of 10 species of caesionid fishes from the Laccadive archipelago, we carried out a molecular phylogenetic analysis, which has helped improve our understanding of the diversity, distribution, and systematics of this poorly known group of fishes. The two speciose genera within Caesionidae, Caesio and Pterocaesio, were revealed to be paraphyletic, and as a result, four names earlier considered as subgenera within Caesionidae (Flavicaesio, Odontonectes, Pisinnicaesio, and Squamosicaesio) were elevated to the status of distinct genera. We also discovered the presence of a new lineage in the Central Indian Ocean, sister to Caesio caerulaurea and Caesio xanthalytos, but distinct from both in several morphological characters and a genetic distance of between 2% and 3% in the mitochondrial COI gene. We describe this lineage as Caesio idreesi, a new species, with a distribution spanning the Laccadive Sea and the Bay of Bengal. Our genetic data also helped confirm the first confirmed records of two species, Pisinnicaesio digramma and Squamosicaesio randalli, from the Central Indian Ocean, and a new distribution record for C. xanthalytos in the Laccadive Sea. Combined, these results have helped bridge key biodiversity knowledge gaps of the family Caesionidae and form an excellent baseline for further investigations on their taxonomy, systematics, and life history.

Investigating possibilities in attracting invasive green anoles with live and artificial baits

Traps are often used as effective tools for eradicating invasive predators. Traps with baits are more effective than those without baits, and live baits are expected to be more effective than artificial ones. However, keeping live baits fresh is often difficult and labour-intensive; thus, artificial baits are to be desired. In this study, we verified the effectiveness of live and artificial baits with or without movement in attracting the invasive green anole Anolis carolinensis. We conducted behavioural experiments in a laboratory with four treatments (live flies, artificial flies without movement, artificial flies with movement and no bait). We placed one of the four bait treatments in a transparent square tube and observed whether a green anole entered the tube (i.e., was attracted) within 30 min. Bait effectiveness was evaluated by comparing the number of attracted and unattracted individuals to that of the control. Green anoles were attracted to live flies but not to artificial flies with or without movement. Our study confirmed that live baits are useful as attractants for green anoles. Artificial baits and those with movement were not attractive, probably because of their monotony. Artificial baits with more complex movements can possibly attract green anoles, and future studies investigating this possibility are needed.

Frequent Allergic Sensitization to Farmed Edible Insects in Exposed Employees

Exposure to insects used in pet food, scientific research, or live fish bait can cause an occupational allergy. The recent shift toward enhanced insect production for human consumption and animal feed will likely expose more employees. To investigate sensitization and symptoms in employees exposed to edible insects in Flanders. Fifteen insect-exposed employees were recruited and sensitization was explored by skin prick test, basophil activation test, and immunoblotting. Lung function, FeNO, histamine provocation, and sputum induction were studied. Airborne dust sampling was performed and proteins were studied by silver stain and immunoblotting. Sixty percent of employees self-reported upper respiratory tract symptoms related to insect exposure. Ten employees (71.4%) had a positive histamine provocation test concentration causing a 20% drop in FEV1 less than 8 mg/mL and four (26.7%) had FeNO levels above 25 ppb. Four employees (30.7%) had a positive skin prick test for at least one insect, and seven (58.3%) had a positive basophil activation test. In eight participants with insect sensitization, four (50%) had co-occurring house dust mite sensitization. Two participants had strong IgE binding to a 50-kDa migratory locust allergen, one to a 25-kDa mealworm allergen, and one to mealworm α-amylase. In one center, facility adjustment resulted in a substantial decrease in the inhalable dust fraction. Insect exposure leads to high levels of sensitization among employees. Most employees reported symptoms of the upper respiratory system, and two-thirds of employees had bronchial hyperreactivity. Prevention and health surveillance will be important in the developing insect-rearing industry.

Potential spread of invasive crayfish used as life bait by Indonesian anglers

ABSTRACT Fishing is part of human culture since ancient times to catch fish. The use of live bait by anglers is an important factor in the spread of invasive aquatic species. To analyze the habits of Indonesian anglers in using freshwater crayfish as live bait, an anonymous online questionnaire was spread via social media in Indonesia. The questionnaire included a series of closed and open-ended questions that investigated various socio-psychological parameters and types of bait used by Indonesian anglers. Redclaw crayfish Cherax quadricarinatus, which is non-indigenous in most of the Indonesian territory, was found to be used by 13% of anglers for this purpose there. These findings illustrate the need for focused management activities. Any potentially invasive non-native species imported into Indonesia, as well as those that are accidentally or deliberately released into the waters, should be regulated, so as not to cause environmental damage.

Operasi penangkapan dan penanganan hasil tangkapan pole and line KM Sari Usaha 09

The utilization of marine biological resources in an effort to increase the production of fishery products has always received serious attention from fishing stakeholders. One of the fishing gear used in exploiting fish resources is pole and line. This study aims to examine pole and line fishing operations and methods of handling the catch on board. This factorrs are important in increasing production with maintained fish quality. This research is descriptive in nature and data collection includes primary data obtained directly from the source or research object, and secondary data obtained indirectly from the research object. Fishing operations include preparation activities, especially ship documents, fishing gear, food supplies, fuel and ice blocks. The operation of pole and line fishing gear uses live bait as a determining factor for fishing success. The types of fish caught are skipjack tuna, yellow fin tuna, dolphinfish, and rainbow runner. The steps taken in the process of handling caught fish on board include preparing catch handling equipment, handling freshly caught fish, and handling fish in holds.

Eastern banded killifish (Fundulus diaphanus diaphanus) in Lake Michigan and connected watersheds: The invasion of a non-native subspecies

Biological invasions can produce severe ecological impacts at both large spatial scales between distantly related species and also smaller spatial scales between conspecifics. We investigated here a potential intraspecific invasion within Lake Michigan and adjacent waters. Banded killifish (Fundulus diaphanus) experienced population increases and spread into novel habitats over recent decades in this region, but managers and policy makers were uncertain if these fish were native western banded killifish (F. d. menona) or instead an invasion by non-native eastern banded killifish (F. d. diaphanus). We applied mitochondrial DNA (mtDNA) barcoding and population genetic analyses to investigate the identity of these fish. We found that new banded killifish populations were the eastern subspecies, including mtDNA haplotypes from the remote mid-Atlantic region, suggesting some introductions from anthropogenic pathways (e.g., live bait trade) rather than only spread from connected, downstream waters (e.g., Lake Erie). Further, population genetic analyses identified eastern banded killifish in our focal region as having low genetic diversity relative to their native range, and relative to western banded killifish populations. Lastly, we found non-native eastern banded killifish were associated with Lake Michigan and connected waters, rather than isolated kettle lakes, and primarily occurred at clearer sites potentially affected by dreissenid mussel invasions. More research is needed on the causes and consequences of eastern banded killifish invasions in Lake Michigan and adjacent waters, including an emphasis on their risk to the conservation of western banded killifish.

Mass synchronization of gonadal maturation in banded knifefish broodstock (Gymnotus cf. carapo)

The banded knifefish Gymnotus cf. carapo (Pisces, Gymnotidae), also known locally as tuvira, is a natural resource of great importance to the Pantanal biome that has been used as live bait in sport fishing. This study investigated the mass synchronization of gonadal development of banded knifefish in captivity by subjecting them to different water electrical conductivity at different time intervals (pre and post conductivity change) and also evaluated the use of ultrasound imaging to identify the sex and phases of ovarian recrudescence of the captive broodstock. Fish were exposed to three different combinations of time intervals (Group 1: 40 + 30 days; Group 2: 45 + 25 days; Group 3: 50 + 20 days) and water conductivity (high: 180 μS/cm, followed by low: 15 μS/cm conductivity, respectively). The control group was kept in low water conductivity throughout the 70-day trial. Based on the results, 93%, 94%, and 86% of mass gonadal maturation of Gymnotus cf. carapo could be achieved by keeping the fish in high water conductivity (180 μS/cm) for 40, 45, or 50 days, and subsequently in low conductivity (15 μS/cm). The sexing and maturation assessment of the fish using ultrasound imaging was fundamental for effectively evaluating the mass gonadal maturation protocol. The combined use of these techniques proved safe in reproductive studies with banded knifefish.