Attraction of preSpawning male shortnose sturgeon Acipenser brevirostrum to the odor of preSpawning females
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Journal of Ichthyology↗
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Validation of a molecular sex marker in three sturgeons from eastern North America
Despite the importance of sex-specific information for sturgeon conservation and management, sex identification has been a major challenge outside of mature adults on spawning grounds. Recent work identified a sex-specific locus ( AllWSex2 ) that appears to be broadly conserved across many Acipenserids, but the assay was not validated for all species within the family. We tested the AllWSex2 marker in three sturgeon taxa (shortnose sturgeon Acipenser brevirostrum , Gulf sturgeon A. oxyrhinchus desotoi , and Atlantic sturgeon A. oxyrhinchus oxyrhinchus ) from the Atlantic and Gulf of Mexico Coasts of North America to validate its use for sex identification. Our results indicate AllWSex2 is conserved in all three taxa, presenting a new opportunity to derive sex-specific information from tissue samples, which are routinely collected from these taxa. We found high concordance (range: 97–100%) between genotypic and phenotypic/histological methods, suggesting the assay is broadly effective. However, the small amount of discordance between the methods (< 3%) suggests further refinement may be possible.
Journal of Applied Ichthyology↗
Overview of biology and aquaculture of Amur sturgeon (Acipenser schrenckii) in China
Amur sturgeon, Acipenser schrenckii is a large riverine species (max. 3 m length and 190 kg weight) native to the Amur River. In the middle Amur River, males first spawn at 7-8 years of age and females at 9-10 years. Due to overfishing and habitat alteration, the abundance of wild stocks has rapidly declined in recent years. Using wild adults, artificial spawning began in the 1950s in China, and since the early 1990s Amur sturgeon has become the most popular sturgeon for aquaculture. The species is adaptive to many conditions of artificial culture, including traditional Chinese fish culture ponds, lakes, reservoirs, and cages. It will grow well on many types of food, and 1-year-old fish reared on commercial diets weigh 900-1200 g. Based on the examination of females reared for broodstock, first full sexual maturity is expected at 5-6 years of age.
Journal of Applied Ichthyology↗
Comparison of mitochondrial DNA control region sequence and microsatellite DNA analyses in estimating population structure and gene flow rates in Atlantic sturgeon Acipenser oxyrinchus
Atlantic sturgeon Acipenser oxyrinchus is large, long-lived, and anadromous with subspecies distributed along the Atlantic (A. oxyrinchus oxyrinchus) and Gulf of Mexico (A. o. desotoi) coasts of North America. Although it is not certain if extirpation of some population units has occurred, because of anthropogenic influences abundances of all populations are low compared with historical levels. Informed management of A. oxyrinchus demands a detailed knowledge of its population structure, levels of genetic diversity, and likelihood to home to natal rivers. We compared the use of mitochondrial DNA (mtDNA) control region sequence and microsatellite nuclear DNA (nDNA) analyses in identifying the stock structure and homing fidelity of Atlantic and Gulf coast populations of A. oxyrinchus. The approaches were concordant in that they revealed moderate to high levels of genetic diversity and suggested that populations of Atlantic sturgeon are highly structured. At least six genetically distinct management units were detected using the two approaches among the rivers surveyed. Mitochondrial DNA sequences revealed a significant cline in haplotype diversity along the Atlantic coast with monomorphism observed in Canadian populations. High levels of nDNA diversity were also observed among populations along the Atlantic coast, including the two Canadian populations, probably resulting from the more rapid rate of mutational and evolutionary change at microsatellite loci. Estimates of gene flow among populations were similar between both approaches with the exception that because of mtDNA monomorphism in Canadian populations, gene flow estimates between them were unobtainable. Analyses of both genomes provided high resolution and confidence in characterizing the population structure of Atlantic sturgeon. Microsatellite analysis was particularly informative in delineating population structure in rivers that were recently glaciated and may prove diagnostic in rivers that are geographically proximal along the south Atlantic coast of the US.
Journal of Applied Ichthyology↗
Potential for restoration of the Roanoke River population of Atlantic sturgeon
The Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) was historically abundant within Albemarie Sound and the Roanoke River in North Carolina, but declined dramatically in the late 1800s in response to intensive fishing. Recent evidence suggests that the population may be recovering, following a statewide prohibition on harvest in 1991. A recruitment index generally increased from 1992 through 2001. Estuarine habitat for juveniles appears to be suitable, resulting in mean growth rates for age 1 fish ranging from 0.59 to 0.81 mm day-1. A restoration goal of 7000-21 000 subadult and adult Atlantic sturgeon was developed for the Roanoke River, based on historical landings records. Bycatch mortality because of commercial gill-netting in Albermarle Sound could affect recovery. Telemetry and netting data indicate that juvenile Atlantic sturgeon in the sound are most abundant in shallow nearshore areas where commercial gill-netting is concentrated. However, immediate mortality rates from survey and commercial gill-netting in Albemarle Sound were only 0-2%. Additional field studies are needed to refine estimates of immediate- and longer-term mortality associated with gill-net bycatch.
Journal of Applied Ichthyology↗
Known lake sturgeon ( Acipenser fulvescens ) spawning habitat in the channel between lakes Huron and Erie in the Laurentian Great Lakes
Bottom substrates and overlying water at three sites where lake sturgeon were reported by others to spawn in the 160-km channel between lakes Huron and Erie were surveyed by boat just before or after the exact time of spawning in 2001 to determine the kinds of substrates present and differences in water quality at the sites. Substrates, examined and photographed using a high-resolution, underwater, video camera, were beds of either rounded cobble (10-40 cm in diameter) and coarse gravel (2-8 cm in diameter) of glacial origin or coal cinders (0.5-12 cm in diameter) of human origin, >1/4 ha in area and >0.3 m in thickness. Water quality, defined as percent of surface light reaching the bottom (range: 0.05-8.7%), Secchi disc depth (range: 2.5-6.5 m), and water current velocity (range: 0.35-0.98 m s-1), differed more than 3-fold between the three sites. Although water depth at these sites (range: 9-12 m) was greater than in many rivers elsewhere used by lake sturgeon, the water current velocities at these sites were in the range in which lake sturgeon were reported to deposit eggs in two small Canadian rivers (0.1-1.1 m s-1).
Journal of Applied Ichthyology↗
Movement and habitat use of green sturgeon Acipenser medirostris in the Rogue River, Oregon, USA
Green sturgeon (Acipenser medirostris) movement patterns and habitat use within the Rogue River, Oregon were evaluated using radio telemetry. Nineteen specimens ranging from 154 to 225 cm total length were caught by gill netting and tagged with radio transmitters during May-July 2000. One tagged green sturgeon was verified as a female near spawning condition. Individual green sturgeons spent more than 6 months in fresh water and traveled as far as river kilometer (rkm) 39.5. Green sturgeon preferred specific holding sites within the Rogue River during summer and autumn months. These sites were typically deep (> 5 m) low-gradient reaches or off-channel coves. Home ranges within holding sites were restricted. All tagged individuals emigrated from the system to the sea during the autumn and winter, when water temperatures dropped below 10??C and flows increased. This species is extremely vulnerable to habitat alterations and overfishing because it spawns in only a few North American rivers and individuals reside within extremely small areas for extended periods of time.
Journal of Applied Ichthyology↗
Migration and habitats of diadromous Danube River sturgeons in Romania: 1998-2000
Upstream migrant adults of stellate sturgeon, Acipenser stellatus (10 in 1998, 43 in 1999) and Russian sturgeon, A. gueldenstaedtii (three in 1999) were captured at river km (rkm) 58-137, mostly in the spring, and tagged with acoustic tags offering a reward for return. The overharvest was revealed by tag returns (38% in 1998, 28% in 1999) and by harvest within 26 days (and before reaching spawning grounds) of the six stellate sturgeon tracked upstream. A drop-back of > 50% of the tagged sturgeon, some to the Black Sea, shows a high sensitivity to interruption of migration and capture/handling/holding. Harvesting and dropback prevented tracking of sturgeon to spawning sites. Gillnetting and tracking of stellate sturgeon showed that the autumn migration ended in early October (river temperature 16??C) and identified a likely wintering area at river km (rkm) 75-76 (St George Branch). Thus, fishery harvesting after early October captures wintering fish, not migrants. Rare shoreline cliffs in the lower river likely create the only rocky habitat for sturgeon spawning. A survey for potential spawning habitats found five sites with rocky substrate and moderate water velocity, all ???rkm 258. Drift netting caught early life-stages of 17 fish species and one sturgeon, a beluga, Huso huso, larva likely spawned at ???rkm 258. All diadromous Danube sturgeons likely spawn at ???rkm 258.
Journal of Applied Ichthyology↗
Understanding sturgeon life history: Enigmas, myths, and insights from scientific studies
No abstract available.
Journal of Applied Ichthyology↗
Use of electronarcosis to immobilize juvenile lake and shortnose sturgeons for handling and the effects on their behavior
Low voltage constant direct current was used to immobilize juvenile lake (Acipenser fulvescens) and shortnose sturgeons (A. brevirostrum). There was no significant difference in time/ the lake or shortnose sturgeons required to exhibit positive rheotaxis between fish immobilized with electricity and control fish (two-way ANOVA, P = 0.11). Fish immobilized with 80 mg L-1 tricaine took a significantly longer time to orient than control fish or fish immobilized with electricity for 5 or 30 min (one-way ANOVA, P = 0.003). Electronarcosis, which produces effects like a chemical anesthetic, is a useful technique for immobilizing juvenile sturgeons for handling. Fish can swim upright as soon as the electricity is turned off, recovery time is shorter than with chemical anesthetics, and the cost of equipment is < 400 USD.
Journal of Applied Ichthyology↗
The representative research animal: Why rainbow trout (Salmo gairdneri Rich.)?
In laboratory research, the rainbow trout has become a counterpart to the white rat, because that fish is an adaptable species available in much of the developed world and stocks from egg through adult are available throughout the year. Moreover, many strains are recognized, and their propagation and laboratory maintenance are not particularly demanding. Also, knowledge of rainbow trout nutrition, husbandry, diseases, immune responses, toxicology, and carcinogenesis exceeds that of any other salmonid or coldwater teleost. The rainbow trout is the logical surrogate species in many studies of other salmonids.
Journal of Applied Ichthyology↗
Mechanisms and function of school formation in subyearling American shad (Alosa sapidissima)
Summary The behavioural repertoire of subyearling American shad ( Alosa sapidissima ) was studied in the laboratory to examine pathways leading to Aggregation and School formation at various group sizes (3–100 fish per 500-liter tank). Three hypotheses were tested: (1) schooling is the dominant behavioural activity of subyearling American shad, (2) development and maintenance of cohesive social behaviour is affected b group size, and (3) survival is a function of group size. Seventeen discrete behaviour patterns were observed. In relation to group size, the amount of time spent Schooling varied directly whereas Following and Aggregating varied inversely. The number of bouts of Parallel orient, Parallel swim, and Pivot also varied inversely with group size. A conceptual model was developed and tested to show how normal schooling behaviour is achieved in small or fragmented groups through intermediary modal action patterns. Sequence analysis showed behavioural diversity to diminish with group size, thereby increasing group cohesion and uniformity of response to stimuli. Probability of survival, determined from weekly mortality in experimental tanks, increased significantly with group size (0.87–0.98 for 3–100 fish). It is hypothesized that survival improves with an increase in the proportion of time spent Schooling, which may increase feeding efficiency, reduce stress, or reduce metabolic expenditures.
Journal of Applied Ichthyology↗
Molecular approaches to fish vaccines
For more than 50 years, researchers have tested a variety of killed, attenuated, and subunit preparations for control offish diseases. The earliest fish vaccines used killed preparations containing whole bacteria, viruses, or parasites and today, several bacterins have become commercially successful with more expected as improved delivery systems and adjuvants are realized. Live, attenuated vaccines have been developed by serial passage of a pathogen in culture or by using naturally occurring mutants and cross-reacting strains. These generally offer excellent protection and are cost-effective, but concerns about residual virulence or their effects on other aquatic species make them difficult candidates for licensing. In recent years, the tools of molecular biology have been applied to construction of a variety of recombinant, engineered, or subunit vaccines for fish. Among the approaches to be discussed are: attenuated strains of viruses and bacteria created by deletion of specific genes associated with virulence, in vitro synthesis of protective antigens from genes cloned into E. coli or baculovirus expression systems, chemical synthesis of peptides that represent protective epitopes, and direct immunization with DNA coding for protective antigens. Preparations representing each of these approaches have been tested in laboratory or field trials with various results and such vaccines promise to be safe and relatively inexpensive if they are able to provide protection when delivered by immersion. A significant advantage of genetically engineered vaccines is the ability to construct multivalent preparations that can protect fish against several pathogens or different strains of the same pathogen. While many of these novel vaccine strategies have been effective at stimulating specific immunity in the laboratory, more work is needed to develop better delivery systems and to overcome potential regulatory concerns.
Journal of Applied Ichthyology↗
Spawning by lake sturgeon ( Acipenser fulvescens ) in the Detroit River
Overfishing and habitat destruction in the early 1900s devastated lake sturgeon ( Acipenser fulvescens ) populations in the Great Lakes. Although a comprehensive restoration strategy for this species was recently drafted by the Michigan Department of Natural Resources, a lack of current data on Great Lakes sturgeon stocks has hindered rehabilitation efforts. Historically, the Detroit River supported one of the largest lake sturgeon populations in the Great Lakes; however, little is known about the current population or its habitat use. The main objective of this study was to determine if lake sturgeon spawns in the Detroit River. As part of a larger study, baited setlines were used to capture lake sturgeon in the Detroit River in the spring and summer of 2000 and 2001. In each year of the study, ultrasonic transmitters were surgically implanted in 10 adult fish to track their movements, evaluate habitat use and identify possible spawning sites. Using telemetry and egg mats to verify spawning activity, one spawning site was located and verified in the Detroit River. Spawning was verified by recovering sturgeon eggs deposited on egg collection mats anchored at the site. Telemetry data suggested that several other possible spawning sites also may exist, however, spawning activity was not verified at these sites.
Journal of Applied Ichthyology↗
Length-weight relationship and a relative condition factor equation for lake sturgeon (Acipenser fulvescens) from the St Clair River system (Michigan, USA)
Several USA state, federal, and Canadian agencies study lake sturgeon (Acipenser fulvescens) within the St Clair River and Lake St Clair, collectively referred to hereafter as the St Clair River (SCR) system. Previously, there has been no set standard for determining condition for SCR system lake sturgeon. Condition measures the variation from the expected weight for length as an indicator of fatness, general well-being, gonad development, etc. The aim of this project was to determine the length weight relationship of lake sturgeon caught from the SCR system, from which a relative condition factor (Kn) equation could be derived. Total length (TL, mm) and weight (W, kg) were measured for 1074 lake sturgeon (101 males and 16 females were identifiable) collected by setline and bottom trawl from the SCR system in May-September, 1997-2002. Analysis of covariance found no difference in the length-weight relationship between sampling gear or sex. Least-squares regression of log10W ?? log10TL produced the overall equation logW = 3.365logTL - 9.320. Using the exponential form of the slope and y-intercept, relative condition factor for lake sturgeon from the SCR system can be calculated as Kn - W/[(4.786 ?? 10-10)(TL3.365)]. Equations for males and females were also developed. Overall, body condition was significantly correlated with both age and girth; no significant difference in Kn by sex was found. In general, the SCR lake sturgeon population was near the upper ends of growth and condition ranges listed in the literature, comparable with those populations that are at similar latitudes. Although condition factors should be interpreted with caution, proper use of a standard equation provides a non-lethal measure of overall fish health that can be used by biologists and managers in ongoing efforts to restore lake sturgeon throughout the Great Lakes. ?? 2005 Blackwell Verlag, Berlin.
Journal of Applied Ichthyology↗
Lake sturgeon population characteristics in Rainy Lake, Minnesota and Ontario
Rainy Lake contains a native population of lake sturgeon Acipenser fulvescens that has been largely unstudied. The aims of this study were to document the population characteristics of lake sturgeon in Rainy Lake and to relate environmental factors to year-class strength for this population. Gill-netting efforts throughout the study resulted in the capture of 322 lake sturgeon, including 50 recaptures. Lake sturgeon in Rainy Lake was relatively plump and fast growing compared with a 32-population summary. Population samples were dominated by lake sturgeon between 110 and 150 cm total length. Age–structure analysis of the samples indicated few younger (<10 years) lake sturgeon, but the smallest gill net mesh size used for sampling was 102 mm (bar measure) and would not retain small sturgeon. Few lake sturgeon older than age 50 years were captured, and maximum age of sampled fish was 59 years. Few correlations existed between lake sturgeon year-class indices and both annual and monthly climate variables, except that mean June air temperature was positively correlated with year-class strength. Analysis of Rainy Lake water elevation and resulting lake sturgeon year-class strength indices across years yielded consistent but weak negative correlations between late April and early June, when spawning of lake sturgeon occurs. The baseline data collected in this study should allow Rainy Lake biologists to establish more specific research questions in the future.
Rainy Lake↗
Lake sturgeon spawning on artificial habitat in the St Lawrence River
In 1996, lake sturgeon ( Acipenser fulvescens ) spawning was documented for the third consecutive year on an artificially placed gravel bed in the St Lawrence River. Two distinct spawning periods were observed in 1996. Spawning initially commenced on 17 June, when water temperature reached 15°C. A second spawning event was documented from 28 June to 1 July (16°C). Sturgeon egg densities were monitored in three transects on egg trays, on the gravel surface, and within interstitial spaces in the gravel. Counts of developing eggs in the gravel bed during both spawning periods were used to estimate a total of 275 000 eggs on the study area (0.075 ha). Average egg density was highest in the transect with the highest water velocities. Lake sturgeon fry were first observed in the gravel on 24 June (15.5°C), and first emergence from the gravel was documented on 28 June. Hatching following the second spawning event commenced on 3 July. Based on assessment of average embryo viability (61.6%) and egg-to-emergent fry survival (17.6%) an estimate of about 171 000 sturgeon eggs hatched, producing over 49 000 emergent fry. Current velocity, substrate particle size, depth of substrate, and maintenance of sediment-free interstitial spaces are important considerations in planning future spawning habitat enhancement projects.
Journal of Applied Ichthyology↗
Growth rates of young-of-year shovelnose sturgeon in the Upper Missouri River
Information on growth during the larval and young-of-year life stages in natural river environments is generally lacking for most sturgeon species. In this study, methods for estimating ages and quantifying growth were developed for field-sampled larval and young-of-year shovelnose sturgeon Scaphirhynchus platorynchus in the upper Missouri River. First, growth was assessed by partitioning samples of young-of-year shovelnose sturgeon into cohorts, and regressing weekly increases in cohort mean length on sampling date. This method quantified relative growth because ages of the cohorts were unknown. Cohort increases in mean length among sampling dates were positively related (P < 0.05, r 2 > 0.59 for all cohorts) to sampling date, and yielded growth rate estimates of 0.80–2.95 mm day −1 (2003) and 0.44–2.28 mm day −1 (2004). Highest growth rates occurred in the largest (and earliest spawned) cohorts. Second, a method was developed to estimate cohort hatch dates, thus age on date of sampling could be determined. This method included quantification of post-hatch length increases as a function of water temperature (growth capacity; mm per thermal unit, mm TU −1 ), and summation of mean daily water temperatures to achieve the required number of thermal units that corresponded to post-hatch lengths of shovelnose sturgeon on sampling dates. For six of seven cohorts of shovelnose sturgeon analyzed, linear growth models ( r 2 ≥ 0.65, P < 0.0001) or Gompertz growth models ( r 2 ≥ 0.83, P < 0.0001) quantified length-at-age from hatch through 55 days post-hatch (98–100 mm). Comparisons of length-at-age derived from the growth models indicated that length-at-age was greater for the earlier-hatched cohorts than later-hatched cohorts. Estimated hatch dates for different cohorts were corroborated based on the dates that newly-hatched larval shovelnose sturgeon were sampled in the drift. These results provide the first quantification of growth dynamics for field-sampled age-0 shovelnose sturgeon in a natural river environment, and provide an accurate method for estimating age of wild-caught individuals. Methods of age determination used in this study have applications to sturgeons in other regions, but require additional testing and validation.
North Dakota↗