Micropterus Research Articles

Characteristics of the black bass tournament fishery in eastern Lake Ontario and the St. Lawrence River

We describe as new species Micropterus pucpuggy Freeman & Freeman (Bartrams Bass), sp. nov., and Micropterus calliurus Freeman & Freeman (Altamaha Bass), sp. nov., which occur allopatrically in four river systems draining the Atlantic Slope of the southeastern United States. In recent decades, biologists and anglers have acknowledged the existence of these two distinctive taxa of black bass, both of which were previously considered synonymous with M. coosae Hubbs & Bailey (Redeye Bass). However, introgression with non-native congeners that have been widely introduced for sport-fishing (including M. henshalli Hubbs & Bailey and M. dolomieu Lacepde) has confounded formal description of M. pucpuggy and M.calliurus. We examined mitochondrial (mtDNA) and nuclear gene sequences of candidate type-specimens of M. pucpuggy and M. calliurus. We then used reduced-representation, short-read sequencing of candidate types along with specimens of six other Micropterus species to identify a series of non-introgressed individuals for each of the two new species. Micropterus pucpuggy and M. calliurus are each reciprocally monophyletic in both mitochondrial and RADseq phylogenies and are diagnosable from all other Micropterus species and from each other in chromatic fin coloration, body pigmentation, and other morphological attributes.

ABSTRACTThe black basses of the southeastern United States are an excellent study group for investigating the relative roles of habitat and biotic interactions for determining species co‐occurrence. This group is comprised of generalist species such as Largemouth Bass Micropterus nigricans, as well as specialist species such as those within the M. coosae complex. Bartram's Bass M. sp. cf. coosae is a provisional species of particular concern endemic to the upper Savannah River basin of Georgia, South Carolina and North Carolina, USA. Bartram's Bass and Largemouth Bass may occur in the same rivers, but do not necessarily co‐occur in the same micro‐ or mesohabitats. Recent surveys in numerous Savannah River tributaries where Bartram's Bass was previously known to have existed have either detected only Largemouth Bass or no black basses at all. The apparent loss of endemic Bartram's Bass and frequent replacement with cosmopolitan Largemouth Bass is concerning from a conservation perspective because it could indicate either (a) ongoing biotic homogenisation via habitat shifts, (b) habitat‐mediated asymmetric interspecific interactions resulting incompetitive exclusion, or (c) some combination of these processes. In this study, we assessed differences in landscape‐level factors and proximity to reservoirs on the occurrence and co‐occurrence of these species using a multispecies occupancy model developed for two or more potentially interacting species. This approach can be used to untangle the relative roles that biotic interactions or habitat covariates have on species distributions. The most compelling model evidence suggested that Bartram's Bass and Largemouth Bass were associated with land cover effects on instream habitat and provided less evidence that co‐occurrence was driven by interspecific interactions. Human land use change and impoundment of free‐flowing rivers have created new opportunities for Largemouth Bass to access upstream lotic habitats and are associated with the loss of lotic habitats and restricted the distribution of Bartram's Bass.

Simple Sequence Repeats (SSRs) and Single Nucleotide Polymorphisms (SNPs) offer distinct yet complementary insights into genetic diversity and population structure. This study compared whole-genome SSRs and SNPs to characterize Largemouth Black Bass (Micropterus salmoides) populations, a critical Chinese aquaculture species. We analyzed the selectively bred 'Zhejiang Black Bass No.1' F4 strain (ZL1f4) against two introduced cultured populations (Anhui: AL, Panzhihua: PL). High-throughput whole-genome resequencing yielded over one million high-quality SNP loci, and 28,250 (LobSTR) and 2,142 (SSRgenotyper) polymorphic SSRs, enabling robust comparative marker assessment. Results consistently demonstrated significantly reduced genetic diversity in selectively bred ZL1f4 (e.g., ZL1f4 average expected heterozygosity via LobSTR: 0.445 vs. AL: 0.536), reflecting artificial selection's genetic consequences. Both marker types revealed population differentiation, but SNPs consistently exhibited superior resolution (e.g., ZL1f4 vs. AL Fst: 0.1049 for SNPs vs. 0.0644 for LobSTR-SSR). Despite diversity differentiation, genetic structure analysis indicated retained shared ancestral components, suggesting selection influenced allele frequencies and heterozygosity, not fundamental genetic architecture. This research underscores SSR and SNP complementary strengths, advocating their integrated application for robust genetic characterization and informing sustainable aquaculture. Findings provide crucial data for effective genetic enhancement and long-term population management of Largemouth black bass, contributing to germplasm and aquatic biodiversity preservation.

Microsatellites (SSRs) are highly polymorphic DNA sequences widely used in genetic research, including parentage assignment. Traditional SSR analysis relies on capillary electrophoresis (CE), which is time-consuming and has limited capacity. Next-generation sequencing (NGS) offers a high-throughput and cost-effective alternative, but existing NGS-based SSR genotyping methods produce results that are incompatible with CE data, increasing the risk of Mendelian inheritance mismatches. This study presents an optimized, targeted, NGS-based approach for SSR genotyping that prioritizes consistency with CE-based results. We optimized SSRseq, a targeted NGS-based SSR genotyping method, by (1) using primer flanking sequences as anchors for BLAST (Basic Local Alignment Search Tool)-based read alignment to reference SSRs, enabling the utilization of both overlapping and nonoverlapping paired-end reads; (2) inferring motif repeat counts from aligned read lengths, tolerating imperfections within the microsatellite repeat array (MRA); and (3) dynamically adjusting motif definition when discrepancies arose between expected and observed MRAs. We evaluated our optimized SSRseq against the original SSRseq and CE using four 10-plex SSR panels for parentage assignment in Largemouth black bass (Micropterus salmoides). The optimized SSRseq substantially improved parentage assignment accuracy. Multiple combinations of two or more optimized SSRseq panels achieved an assignment rate of 1.000 and an accuracy rate of 0.950, whereas the original SSRseq's highest accuracy was 0.900, requiring all four panels. The optimized method also showed high concordance with CE genotyping at several tested loci. This optimized SSRseq approach provides a robust, efficient, and cost-effective tool, leveraging NGS for accurate SSR genotyping in parentage assignment and other genetic analyses while minimizing Mendelian inheritance mismatches.

Using angler-submitted records to interpret the spatial seasonality of a large predator (Black bass, Micropterus spp.)

Black bass (Micropterus spp.) are the most important warmwater game fishes in the United States. They have high socioeconomic and recreational value and support an important aquaculture industry. Since 2008, fisheries managers have been reporting the observation of hyperpigmented melanistic lesions (HPMLs) on smallmouth bass (M. dolomieu) in different ecoregions of the United States. Similar HPMLs have been observed in largemouth bass (M. nigricans) since the 1980’s. Here, we report a close association between novel adomaviruses and the hallmark blotchy clinical presentation of hyperpigmented lesions on the skin smallmouth and largemouth black bass and provide evidence that satisfies Rivers’ postulates. The two adomaviruses are structurally and phylogenetically similar but share only 68.0% identity at aligned nucleotide sites and each has been found in only one host species to date. The manifestation of this skin disease appears to be seasonal in both species, primarily affects adults and is of unknown health consequence. Although the significance of infection to fish health remains unclear, understanding the disease ecology of these can inform biosecurity and the interjurisdictional movement of individuals. Moreover, as hyperpigmentation in other fish species is often idiopathic, our findings reframe perspectives for future investigations into this clinical presentation in other species.

ABSTRACT Objective To inform the conservation and management of the popular sport fish comprising the Redeye Bass Micropterus coosae complex, our objective was to estimate growth parameters of Redeye Bass complex species (REB) from all four native watersheds in the Mobile River basin, Alabama, where they occur. Methods We used single-nucleotide polymorphism genotyping to confirm the genetic purity of fish that were used to estimate mean total length at age across all four REB by utilizing von Bertalanffy growth curves and catch curves that were fitted to estimate survival/mortality rates. Results We collected a total of 322 genetically pure REB specimens via hook-and-line angling from 27 different streams in the Black Warrior (N = 47 fish), Coosa (N = 126), Cahaba (N = 52), and Tallapoosa (N = 97) River drainages. Growth analysis indicated that members of the Redeye Bass complex are the slowest growing of the black basses Micropterus spp., with asymptotic length parameter estimates ranging from 257 to 308 mm. We predicted that REB from these drainages would attain a length of 254 mm after 6.9 years (Tallapoosa River drainage) to 10.3 years (Black Warrior River drainage). Catch-curve analysis indicated that the total instantaneous mortality rate did not differ among drainages, and the estimate of 0.38 year−1 was within the range of expected background natural mortality, which suggests that fishing mortality is likely low in these systems. Conclusions Very little is currently known about basic life history characteristics of endemic black bass species, such as the Redeye Bass complex. Knowledge of species-specific growth rates and fishing mortality should better inform the conservation and management of these unique riverine species by providing data for length and bag limit considerations and by establishing baseline data to continue the monitoring and evaluation of growth parameters.

ABSTRACT Objective Intersexual variation within fish species can be observed through morphological, physiological, and behavioral differences. Although this variation can have important implications for the ecology and management of many fish species, challenges associated with the methods to determine sex have been a limitation for research in this area. This study evaluated the feasibility of portable ultrasonography as a noninvasive tool to determine sex for two monomorphic black bass species, the Largemouth Bass Micropterus nigricans and Smallmouth Bass M. dolomieu. Methods Sex was estimated for wild black bass (n = 123) by using portable ultrasonography and was verified by laboratory dissection to assess accuracy. Our investigation also included a case study involving age-3 tank-raised Smallmouth Bass that were exposed to nonnatural photoperiod and temperature conditions. Results Ultrasonography proved effective for sexing black bass, achieving an accuracy of 92.7%. Mature ovaries were readily identifiable through sonograms, whereas mature testes in males were more challenging to detect. The technique also showed potential for accurately sexing tank-raised Smallmouth Bass. Conclusions Portable ultrasound is a rapid, accurate, and noninvasive tool for the sex identification of black bass, supporting its integration into field and laboratory studies. The methods described in this study should be evaluated in other monomorphic species and may contribute to the effective management of fish populations.

ABSTRACT Objective Angler harvest of Smallmouth Bass Micropterus dolomieu is thought to generally have followed a similar pattern as Largemouth Bass Micropterus nigricans, decreasing since the 1980s through the rise in voluntary catch and release. However, Smallmouth Bass can be long lived and slow growing, and occupy different types of systems, and angler harvest may be higher in some regions, suggesting that harvest could alter populations. Yet, little contemporary Smallmouth Bass harvest information is available in lotic systems in the northern Midwest. Our objectives were to assess angler size-selective harvest, the number of Smallmouth Bass caught and harvested, and the effect of harvest on Smallmouth Bass survival. Methods We tagged 2,165 Smallmouth Bass from May 23 to September 17, 2019, and from May 19 to September 28, 2021, in three bays of Lake Oahe, South Dakota; estimated weekly exploitation; and assessed potential angler size-selective harvest using angler tag returns. We used Cormack–Jolly–Seber models to test if harvest mortality was compensatory or additive. Results We found that weekly Smallmouth Bass exploitation ranged from 0% to 11.9%, with the highest harvest occurring during late May and early June while generally decreasing through late September. Mean annual Smallmouth Bass exploitation per bay was as low as 13.5% (12.3–14.9%) in Spring Creek during 2021 and as high as 19.4% (17.7–21.4%) in Okobojo Bay during 2021. Anglers harvested larger Smallmouth Bass (median total length = 375 mm) and released smaller Smallmouth Bass (median total length = 338 mm). Smallmouth Bass weekly apparent survival per bay ranged from 0.427 to 0.999 and declined with increasing water temperatures and exploitation, suggesting that harvest mortality is additive. Conclusions Our findings support our hypotheses that anglers harvest larger individuals than those they release, exploitation is higher than other black bass exploitation estimates, and harvest mortality was additive, indicating that Smallmouth Bass angler harvest has the potential to alter populations and needs to be considered when making management decisions.

The Zimapan hydropower plant built in 1995 was the first project to take advantage of Mexico's City wastewater for electric power generation. This tropical reservoir receives pollutants that affect water quality from municipal, agricultural, and industrial wastewater through the Tula and San Juan rivers. The study considered the changes in the physicochemical parameters (surface to 20 m depth) for May (wet warm), November (wet cold-after rains), and February (dry cold) in seven dam sites: two lotic, two transitional, and three lentic sites. Mean values ranges were temperature 20.71-24.38 °C, 1.59-7.56 mg/l dissolved oxygen, Secchi disk transparency 2.26-3.98 m, pH 7.12-8.40, electrical conductivity 48-1334 µS/cm, total nitrogen 14.20-30.74 mg/l, total phosphorus 10.45-15.83 mg/l, and dissolved organic carbon 9.11-20.63 mg/l. In November, all the reservoir surface water was hypoxic due to increased dissolved organic carbon by river input. Even though dissolved oxygen has a seasonal variation, this reservoir has a sustainable fishery of tilapia and black bass (~400 tons/y). The dam is meromictic and hypereutrophic, with seasonal water quality variations with no significant spatial variations. Water quality variation observed in this study can be useful to Mexican decision-makers on water and fisheries management, prevent massive fish kills, and be a support guide for commercial and sport fishers.

Impoundment construction has resulted in the alternation and loss of fluvial habitats, threatening the persistence of many native fishes. Compounding this threat, non-native species stocked into impoundments often invade interconnected fluvial habitats, where they may negatively affect native species. Black basses (genus Micropterus) are popular sportfishes with divergent ecologies: some taxa are tolerant of impoundments and widely stocked to create fishing opportunities, whereas others are endemic fluvial specialists that are threatened by introgression with non-native congeneric taxa. We investigated whether impoundments facilitate non-native invasion and introgression in two case study systems: Lake Lanier, Georgia, and Lake Tenkiller, Oklahoma. In both case studies, native fluvial taxa inhabited upstream tributaries and a non-native was established within the downstream impoundment. Results from longitudinal surveys of upstream tributaries provided clear evidence that non-natives invaded upstream from impoundments, and in some cases, extensive introgression with native taxa also occurred. Variation in spatial trends of invasion and directionalities of introgression across case studies provided insights into eco-evolutionary drivers. Within the riverscapes studied, proximity to impoundment appeared to influence invasion and introgression dynamics, and in one case, stream size was also influential. Introgression rates also varied markedly across the species pairs studied-from very little introgression to the onset of hybrid swarming-illustrating the importance of underlying eco-evolutionary mechanisms such as habitat alteration, propagule pressure, and reproductive isolation. Our results underscore the need to consider the upstream influences of impoundments, and the non-natives that invade from them, to create more holistic riverscape conservation plans for fluvial fishes, including native black basses.

Advancing black bass management and conservation to benefit fish populations, fisheries, and people

Florida bass, Micropterus salmoides , an economically important sport fish species, has great potential for indoor recirculation aquaculture systems (RAS), but knowledge about optimal dietary requirements during the early life history stages remains unresolved. Thus, the objective of this study was to determine a first‐feeding protocol for Florida bass indoor RAS culture. Four dietary treatments were tested: treatment 1 received rotifers with enriched Artemia , treatment 2 received rotifers with nonenriched Artemia , treatment 3 received only enriched Artemia , while treatment 4 received nonenriched Artemia . At 5 days posthatch (DPH), all treatments received a microdiet. Fish were sampled in regular intervals for total length (TL), body area (BA), myotome height (MH), jaw length (JL), eye diameter (ED), oil droplet area (ODA), and yolk area (YA). Condition index (CI), yolk utilization efficiency (YUE), and yolk utilization rate (YUR) were calculated. Wet weight, tank biomass, and survival were also recorded at 25 DPH. Results showed that Artemia enrichment did not influence any of the morphometric traits. Adding rotifers or enriched artemia did not significantly impact weight, final biomass, or survival at 25 DPH for Florida bass. Larvae fed rotifers exhibited a significant increase in morphometric development (TL, BA, MH, JL, ED, and CI) and were more efficient and faster at converting yolk reserves to body size. We conclude that a dietary regimen including rotifers allows Florida bass larvae to transition to exogenous energy sources faster and increase development. The present study improves understanding of black bass dietary requirements during critical early life history stages to increase hatchery efficiency.

ABSTRACTRegional factors correlated with recruitment of black bass (largemouth bass; Micropterus nigricans and smallmouth bass; Micropterus dolomieu), two important fishes, are rarely studied, despite the importance of recruitment variation in influencing fish populations. We sought to identify factors that drove variation in age‐0 and age‐1 black bass abundance. Age‐0 or age‐1 black bass catch per unit effort (CPUE) in reservoirs in Kansas and Illinois, USA, was positively correlated with local short‐term (i.e., mean April precipitation) environmental variables. In contrast, age‐0 or age‐1 black bass CPUE was generally negatively correlated with long‐term environmental variables and river regulation metrics (i.e., reservoir elevation) in the Mississippi and Missouri river reservoirs. Our findings highlight that consideration of spatiotemporal scale is important when managing black bass populations.

Abstract Water diversions that support agricultural and municipal use result in fish mortality through entrainment and impingement. Additionally, this infrastructure may attract both predators and prey fishes, thereby increasing predation rates and prey mortality near these anthropogenic contact points. The Sacramento–San Joaquin Delta (the Delta) in California's Central Valley is a tidal freshwater ecosystem that exports large volumes of water for municipal and agricultural use while at the same time providing valuable migratory and rearing habitat for imperilled fishes. Emigrating juvenile salmonids experience high mortality in the Delta, with predation by non‐native fishes contributing substantially. Therefore, this study had three main objectives. First, we determined if small water diversions aggregated piscivorous fishes like other similar structures in freshwater ecosystems. Second, we determined how small diversions may influence juvenile salmon predation risk in conjunction with other known predation risk factors (e.g. predator abundance, temperature and depth). Third, we assessed the predator assemblage, abundance and distribution to determine the likely predator composition in objectives one and two. Throughout the spring of 2021, we used ARIS (adaptive resolution imaging sonar; Sound Metrics) sonars to compare piscivore abundance at 30 water diversions in the north Delta to shorelines adjacent to diversions that did not contain these structures. We used predation event recorders (PERs) to assess the predation risk juvenile salmonids were exposed to, with linear distance (m) from diversions, and other predation risk factors in the north Delta. Finally, we used a boat electrofishing survey to determine the piscivore assemblage and compare spatial trends in black bass (Micropterus spp.) CPUE and relative abundance throughout these waterways. Piscivore abundance was greater near small water diversions than at adjacent shorelines and the predation risk of juvenile salmonids increased with diversion proximity. Additionally, predation risk increased with increasing piscivore abundance and decreasing water depth. The north Delta predator assemblage was dominated by black basses (Micropterus spp.), which likely drove the negative relationship of predation risk with water depth, given habitat requirements of these species. Furthermore, increasing smallmouth (Micropterus dolomieu) and spotted bass (Micropterus punctulatus) abundance in our northern study sites may have weakened temperature effects on predation, given metabolic requirements of these species. Our work demonstrated that small water diversions are likely to increase mortality of endangered salmonids, and that the north Delta predator assemblage was different than recorded by previous work in this system, changing predation risk factors. Although more work is needed to determine the population level impacts of diversions, the ubiquitous distribution of these structures warrants management solutions to reduce mortality from this source. These results indicate that in addition to entrainment and impingement, water diversions may increase mortality of small‐bodied fishes by attracting predators and elevating predation risk. Given the continual human demand for freshwater, predator–prey interactions should be considered along with entrainment and impingement when assessing intake infrastructure mitigation, especially when diversions co‐occur along migratory routes and essential habitat of imperilled fishes.

Simple SummaryA new species of Micropterus (Black Basses) is described from Lake Erie. This species was historically thought to be the Largemouth Bass, Micropterus nigricans. It is distinguished from previously described Micropterus spp. by morphological characters.This previously undescribed species of Micropterus is described from collections in Lake Erie. The species was first recognized by the tri-colored tail of juveniles. This tri-colored tail, the presence of bold parallel lines ventral to the lateral band, and scales in the inter-radial membranes of the dorsal fin distinguish it from Micropterus nigricans. The large mouth that extends past the eye distinguishes it from Micropterus punctulatus.

Abstract Benefits to wildlife communities stemming from the protection of a single species have been documented in terrestrial and marine systems but remain understudied within the context of freshwater‐protected areas (FPAs). We used five long‐standing (>80 years) FPAs in three lakes in eastern Ontario, Canada, which were initially established to protect native black bass (Micropterus spp.) from angling exploitation, to assess whether this protection affected wildlife communities found in the riparian areas of these FPAs. From May to July 2021, we used baited remote camera traps and visual surveys to assess species diversity within and outside of FPAs. We recorded 61 species spanning mammalian, avian and herpetofauna taxa, with the two assessment methods identifying unique sets of species (23% overlap). Camera traps showed that animals were more active in riparian areas during the day (62% of detections) than at night. FPAs had a variable but overall positive influence on riparian wildlife biodiversity, hosting more bird, mammal, amphibian and reptile species than non‐protected areas and having higher species richness. FPAs differed from other sites in the lakes by having higher habitat complexity, less human infrastructure and less human use, which potentially contributed to these differences. This study raises awareness that even small FPAs can have legacy, umbrella‐type benefits that extend beyond fishes to the wildlife that use the adjacent riparian areas.

Recreational angling of nesting largemouth bass (Micropterus nigricans) and smallmouth bass (M. dolomieu) can greatly increase nest abandonment, and in the northern clines of their range, decrease recruitment. This is the case in eastern Ontario, where high levels of non-compliance and difficult to enforce regulations have impacted black bass (Micropterus spp.) conservation and management. Effective January 1, 2024 until December 31st, 2025, novel and experimental fishing sanctuaries were imposed on portions of Charleston Lake and Opinicon Lake that prohibit recreational fishing of all types from April 15th to the Friday before the first Saturday in July (encompassing the full bass reproductive season). As part of the formal process to institute these experimental regulations, public comments were collected on the Environmental Registry of Ontario. We examined those comments and identified supportive and non-supportive themes related to these experimental regulations. While a majority of stakeholders were in support of the new regulations, we also noted sub-themes that may hinder regulation acceptance. Those sub-themes include: a perceived lack of enforcement negating the potential benefits of the sanctuaries, under-estimation of the extent of non-compliance with existing regulations such that new regulations are unnecessary, misunderstanding and misinformation, as well as distrust of government and the academic research community. Understanding and addressing these stakeholder perspectives will help researchers studying the new sanctuary areas and managers understand any lack of compliance while informing future decisions about bass management in eastern Ontario and beyond.

Abstract Objective Suwannee Bass Micropterus notius are a unique black bass that are endemic to riverine systems in Georgia and Florida, USA. Despite their “near threatened” status by the International Union for Conservation of Nature's Red List, Suwannee Bass are a popular sport fish that can be harvested throughout their range under a single harvest regulation with all black basses (genus Micropterus). However, a single harvest regulation may have disproportion effects on Suwannee Bass because of their rarity, limited distribution, and sex-specific growth patterns. Methods Boat electrofishing was used to collect Suwannee Bass and Largemouth Bass M. nigricans from both the Withlacoochee and Ochlockonee rivers to assess population demographics and angler exploitation. Common fisheries assessment metrics were calculated and annual exploitation rate was estimated from high reward (US$100) tags under simulated variability in tag loss and angler reporting rates. Result We observed different relative abundance and size structure among river systems. Electrofishing catch per unit effort of Suwannee Bass was higher in the Withlacoochee River (6.89 fish/h) than the Ochlockonee River (2.01 fish/h). Length-frequency histograms suggested a wide breadth of lengths and presumed ages except for a lack of stock size Suwannee Bass in the Ochlockonee River. Eight percent of monetary reward tags were returned from anglers, yielding an overall exploitation estimate of 3.2%. Conclusion Annual angler exploitation rates of Suwannee Bass and Largemouth Bass were low (<9.1%) in the Withlacoochee and Ochlockonee rivers of Georgia. Low exploitation coupled with a wide breadth of lengths and ages suggest these populations are currently not at risk of overexploitation.