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Documented distribution of Gulf Sturgeon in North America, determined from acoustic and archival telemetry projects. The orange asterisks mark the easternmost and westernmost locations of confirmed detections of acoustic-tagged Gulf Sturgeon. Gulf Sturgeon spawn in coastal rivers including the eight shown on this map. Spawning and non-spawning Gulf Sturgeon typically remain in coastal rivers until fall and occupy estuarine and nearshore marine waters during winter. Yellow triangles indicate winter concentration areas for Gulf Sturgeon from two or more river systems. The 100 m isobath is shown as the light blue areas near the coast. doi:10.1371/journal.pone.0071552.g002 

Documented distribution of Gulf Sturgeon in North America, determined from acoustic and archival telemetry projects. The orange asterisks mark the easternmost and westernmost locations of confirmed detections of acoustic-tagged Gulf Sturgeon. Gulf Sturgeon spawn in coastal rivers including the eight shown on this map. Spawning and non-spawning Gulf Sturgeon typically remain in coastal rivers until fall and occupy estuarine and nearshore marine waters during winter. Yellow triangles indicate winter concentration areas for Gulf Sturgeon from two or more river systems. The 100 m isobath is shown as the light blue areas near the coast. doi:10.1371/journal.pone.0071552.g002 

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Worldwide, sturgeons (Acipenseridae) are among the most endangered fishes due to habitat degradation, overfishing, and inherent life history characteristics (long life span, late maturation, and infrequent spawning). As most sturgeons are anadromous, a considerable portion of their life history occurs in estuarine and marine environments where they...

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Context 1
... hydrograph of a sturgeon-bearing river). In some areas, introduction of non-native sturgeons and hybridization between species (e.g. Scaphirhynchus) due to habitat alteration and/or unintentional release from aquaculture (e.g. in Europe) makes understanding the movement and life history of introduced sturgeons or hybrid populations an important conservation consideration [12], [13]. Knowledge about movement and the spatial distribution of populations can also improve population assessments and help in specifying suitable management or recovery plans. Population assessments are still lacking for most species and are often hindered by an insufficient understanding of spatial distribution. Sturgeon species and/or populations with an anadromous life-history strategy may require assessment models that account for the seasonal movement patterns of different life-history stages exploited by fisheries [14], [15]. Tagging data can be incorporated into spatially explicit models to allow more accurate estimation of fishing mortality rates experienced by different age classes where fishing intensity varies by area [14], [16]. Insufficient data for parameterisation of models for migratory species with complex life histories can lead to large uncertainties in resource assessment and the likely effects of alternative management actions. The lack of data for key parameters of population dynamics has been identified as a contributor to the depleted and endangered status of many sturgeon populations throughout their range [17], [18]. Below, we present recent studies of the Gulf and Green Sturgeon to show how the information gained from these representative studies has been used to direct subsequent activities toward species conservation and the protection of key habitats. 1.2.1. Gulf Sturgeon. The anadromous Gulf Sturgeon, Acipenser oxyrinchus desotoi , a subspecies of the Atlantic Sturgeon, Acipenser oxyrinchus , occurs in most Gulf of Mexico river systems from the mouth of the Mississippi River to the west coast of Florida (Figure 2). Both mature and immature Gulf Sturgeon undergo freshwater migrations, typically entering coastal rivers in March or April and outmigrating to the ocean in September or October [19]. The cool-water period of estuarine or marine residency is critical for growth and reproduction, as Gulf Sturgeon do not feed during their freshwater residency. Early information about Gulf Sturgeon distribution and migration came primarily from commercial fishing [20]. Fishing operations in individual rivers were mostly short-lived (due to overharvest and subsequent fishery closures, as is typical for many in-river sturgeon fisheries), but the catches did provide some insights into the timing and extent of migration. More detailed information came from surveys in the 1980s conducted in response to declining catches and the species’ listing by the state of Florida as ‘‘threatened’’ [21], [22]. Marking with conventional tags mostly showed the range and extent of migration (e.g. recaptures of tagged fish by anglers below a dam or by commercial shrimp trawlers in Gulf of Mexico waters), whereas the first use of electronic tags (and manual/mobile tracking) provided insights about holding, staging, and spawning areas [22]; the use of radio tags in this study allowed the authors to characterize occupied riverine habitats in the Apalachicola River and to relate the timing of upstream and downstream migrations to environmental cues. Radio transmitters worked well for manual tracking of Gulf Sturgeon over long distances in rivers, but these transmitters cannot be detected in brackish or marine water. In the late 1980s a telemetry study was conducted wherein Gulf Sturgeon were tagged with both radio and sonic tags [23]. This was also the first Gulf Sturgeon study to use stationary receivers to detect and log passage events (in this case, to detect sonic tags as fish moved through barrier island passes [23]). The listing of Gulf Sturgeon in 1991 as a threatened species under the U. S. Endangered Species Act provided a further boost to research activity. For example, radio tracking studies in the Choctawhatchee River were initiated to identify potential spawn- ing sites, with confirmation through the use of artificial substrates to collect the adhesive eggs of Gulf Sturgeon [24]. Deployment of artificial substrates in a grid design provided fine-scale information about spawning habitat in the Suwannee River [25]. Marine habitat studies using sonic tags (and more recently, archival temperature-logging and pop-up archival tags) showed that Gulf Sturgeon sometimes moved long distances along the shoreline and primarily used shallow nearshore areas [26–29]. The fish occupying these marine habitats were often from multiple river systems; for example, [27] reported that Gulf Sturgeon from the Yellow, Choctawhatchee, and Apalachicola rivers were located within a 25-km stretch of coastline (eastern winter concentration area shown on Figure 2). The co-occurrence of Gulf Sturgeon from the Pearl and Pascagoula rivers has been documented [29] in the concentration area off Mississippi (western area shown on Figure 2). Thus, marine and estuarine threats and management efforts may affect more than one population. Genetic studies have also aided in understanding Gulf Sturgeon migration patterns. For example, it has been shown that within a basin, genetic structure exists at least at the drainage level and possibly at the level of tributary rivers within the basin [30]. The genetic analyses were helpful in interpreting telemetry results since some fish were tagged outside their natal drainage and others were captured or detected in multiple drainages. These research results formed the basis for the Gulf Sturgeon recovery plan and led to the designation of critical habitats. These important habitats included upper-basin spawning sites with limestone bluffs and outcroppings, estuarine and marine feeding sites with preferred substrates and benthic fauna, and summer resting areas. Genetic results showed strong natal river fidelity, so critical habitat was defined in each of the seven river systems containing currently reproducing populations (Pearl, Pascagoula, Escambia, Yellow/Blackwater, Choctawhatchee, Apalachicola, and Suwannee). This resulted in designation of nearly 2,800 river km as critical habitat for conservation of the species. 1.2.2. Green Sturgeon. In contrast to the relatively well- studied Gulf Sturgeon, the North American Green Sturgeon was little studied until 2002, when the US National Marine Fisheries Service received a petition to list it under the US Endangered Species Act. A severe lack of demographic and basic life-history information hampered the subsequent status review [31]. A particularly troubling unknown was the population origin(s) of Green Sturgeon that form dense aggregations in certain estuaries during summer months. Green Sturgeon were known to use just three rivers for spawning (the Sacramento and Klamath rivers in California, and the Rogue River in Oregon), and to spend much of their lives in marine waters between Alaska and Baja California (Figure 3). The purpose of the summertime estuarine aggregations was unknown, as was the proportion of Green Sturgeon exhibiting this aggregation behaviour. Green Sturgeon in these aggregations are vulnerable to capture in gillnet fisheries that target White Sturgeon and Pacific salmon species, and face environmental threats from activities associated with shellfish aquaculture and industrial activities in the estuaries where they aggregate. The recent development of new telemetric tagging systems made it feasible to rapidly close some of these information gaps. Initial work focused on Green Sturgeon in the Rogue River, using radio and acoustic tags to learn that Green Sturgeon migrate into rivers in the early spring for spawning in up-river areas, and then hold in deep pools over the summer prior to emigration in the fall when flows rise with the onset of the rainy season [32]. Tagged sturgeon returned to the river to spawn every two to four years [33]. Rogue River fish were also tagged with pop-off archival tags (PAT), which revealed that they remain in fairly shallow water (50–80 m) when in the coastal ocean, and showed that they migrate north to the west coast of Vancouver Island in the fall [34]. A broader study using acoustic tags showed that Green Sturgeon make extensive seasonal migrations among spawning areas, over-summering in various estuaries and bays, and overwintering areas in the coastal ocean, with many individuals using areas around northern Vancouver Island [35], [36]. Further PAT work, using longer tag deployments, also showed this seasonal migration pattern, and fairly constrained depth and temperature distributions during the winter. Acoustic tags also revealed extensive use of and movement among non-natal estuaries. Green Sturgeon from different populations mixed together in common estuaries, but at different rates. Natal estuaries were used almost exclusively by fish from the associated natal river [36]. Green Sturgeon were also shown to have diverse patterns of migration within and among populations. Within the Sacramento River, acoustic tags revealed that a seasonal water diversion dam was a serious impediment to the spawning migration of Green Sturgeon [37]. Habitat data associated with tag detections was used to gain further insight into freshwater [38] and fine 2 [39] and coarse- scale [40] marine habitat preferences and seasonal patterns of distribution. Captive rearing of Green Sturgeon is providing important information on salinity tolerance and the timing for successful transition to marine waters, as well as optimal temperature for egg hatching, embryogenesis, and larval and juvenile survival [41–46]. In summary, the application of electronic tag technology to study Green Sturgeon revealed novel, reliable, and useful/relevant information ...
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... and/or unintentional release from aquaculture (e.g. in Europe) makes understanding the movement and life history of introduced sturgeons or hybrid populations an important conservation consideration [12], [13]. Knowledge about movement and the spatial distribution of populations can also improve population assessments and help in specifying suitable management or recovery plans. Population assessments are still lacking for most species and are often hindered by an insufficient understanding of spatial distribution. Sturgeon species and/or populations with an anadromous life-history strategy may require assessment models that account for the seasonal movement patterns of different life-history stages exploited by fisheries [14], [15]. Tagging data can be incorporated into spatially explicit models to allow more accurate estimation of fishing mortality rates experienced by different age classes where fishing intensity varies by area [14], [16]. Insufficient data for parameterisation of models for migratory species with complex life histories can lead to large uncertainties in resource assessment and the likely effects of alternative management actions. The lack of data for key parameters of population dynamics has been identified as a contributor to the depleted and endangered status of many sturgeon populations throughout their range [17], [18]. Below, we present recent studies of the Gulf and Green Sturgeon to show how the information gained from these representative studies has been used to direct subsequent activities toward species conservation and the protection of key habitats. 1.2.1. Gulf Sturgeon. The anadromous Gulf Sturgeon, Acipenser oxyrinchus desotoi , a subspecies of the Atlantic Sturgeon, Acipenser oxyrinchus , occurs in most Gulf of Mexico river systems from the mouth of the Mississippi River to the west coast of Florida (Figure 2). Both mature and immature Gulf Sturgeon undergo freshwater migrations, typically entering coastal rivers in March or April and outmigrating to the ocean in September or October [19]. The cool-water period of estuarine or marine residency is critical for growth and reproduction, as Gulf Sturgeon do not feed during their freshwater residency. Early information about Gulf Sturgeon distribution and migration came primarily from commercial fishing [20]. Fishing operations in individual rivers were mostly short-lived (due to overharvest and subsequent fishery closures, as is typical for many in-river sturgeon fisheries), but the catches did provide some insights into the timing and extent of migration. More detailed information came from surveys in the 1980s conducted in response to declining catches and the species’ listing by the state of Florida as ‘‘threatened’’ [21], [22]. Marking with conventional tags mostly showed the range and extent of migration (e.g. recaptures of tagged fish by anglers below a dam or by commercial shrimp trawlers in Gulf of Mexico waters), whereas the first use of electronic tags (and manual/mobile tracking) provided insights about holding, staging, and spawning areas [22]; the use of radio tags in this study allowed the authors to characterize occupied riverine habitats in the Apalachicola River and to relate the timing of upstream and downstream migrations to environmental cues. Radio transmitters worked well for manual tracking of Gulf Sturgeon over long distances in rivers, but these transmitters cannot be detected in brackish or marine water. In the late 1980s a telemetry study was conducted wherein Gulf Sturgeon were tagged with both radio and sonic tags [23]. This was also the first Gulf Sturgeon study to use stationary receivers to detect and log passage events (in this case, to detect sonic tags as fish moved through barrier island passes [23]). The listing of Gulf Sturgeon in 1991 as a threatened species under the U. S. Endangered Species Act provided a further boost to research activity. For example, radio tracking studies in the Choctawhatchee River were initiated to identify potential spawn- ing sites, with confirmation through the use of artificial substrates to collect the adhesive eggs of Gulf Sturgeon [24]. Deployment of artificial substrates in a grid design provided fine-scale information about spawning habitat in the Suwannee River [25]. Marine habitat studies using sonic tags (and more recently, archival temperature-logging and pop-up archival tags) showed that Gulf Sturgeon sometimes moved long distances along the shoreline and primarily used shallow nearshore areas [26–29]. The fish occupying these marine habitats were often from multiple river systems; for example, [27] reported that Gulf Sturgeon from the Yellow, Choctawhatchee, and Apalachicola rivers were located within a 25-km stretch of coastline (eastern winter concentration area shown on Figure 2). The co-occurrence of Gulf Sturgeon from the Pearl and Pascagoula rivers has been documented [29] in the concentration area off Mississippi (western area shown on Figure 2). Thus, marine and estuarine threats and management efforts may affect more than one population. Genetic studies have also aided in understanding Gulf Sturgeon migration patterns. For example, it has been shown that within a basin, genetic structure exists at least at the drainage level and possibly at the level of tributary rivers within the basin [30]. The genetic analyses were helpful in interpreting telemetry results since some fish were tagged outside their natal drainage and others were captured or detected in multiple drainages. These research results formed the basis for the Gulf Sturgeon recovery plan and led to the designation of critical habitats. These important habitats included upper-basin spawning sites with limestone bluffs and outcroppings, estuarine and marine feeding sites with preferred substrates and benthic fauna, and summer resting areas. Genetic results showed strong natal river fidelity, so critical habitat was defined in each of the seven river systems containing currently reproducing populations (Pearl, Pascagoula, Escambia, Yellow/Blackwater, Choctawhatchee, Apalachicola, and Suwannee). This resulted in designation of nearly 2,800 river km as critical habitat for conservation of the species. 1.2.2. Green Sturgeon. In contrast to the relatively well- studied Gulf Sturgeon, the North American Green Sturgeon was little studied until 2002, when the US National Marine Fisheries Service received a petition to list it under the US Endangered Species Act. A severe lack of demographic and basic life-history information hampered the subsequent status review [31]. A particularly troubling unknown was the population origin(s) of Green Sturgeon that form dense aggregations in certain estuaries during summer months. Green Sturgeon were known to use just three rivers for spawning (the Sacramento and Klamath rivers in California, and the Rogue River in Oregon), and to spend much of their lives in marine waters between Alaska and Baja California (Figure 3). The purpose of the summertime estuarine aggregations was unknown, as was the proportion of Green Sturgeon exhibiting this aggregation behaviour. Green Sturgeon in these aggregations are vulnerable to capture in gillnet fisheries that target White Sturgeon and Pacific salmon species, and face environmental threats from activities associated with shellfish aquaculture and industrial activities in the estuaries where they aggregate. The recent development of new telemetric tagging systems made it feasible to rapidly close some of these information gaps. Initial work focused on Green Sturgeon in the Rogue River, using radio and acoustic tags to learn that Green Sturgeon migrate into rivers in the early spring for spawning in up-river areas, and then hold in deep pools over the summer prior to emigration in the fall when flows rise with the onset of the rainy season [32]. Tagged sturgeon returned to the river to spawn every two to four years [33]. Rogue River fish were also tagged with pop-off archival tags (PAT), which revealed that they remain in fairly shallow water (50–80 m) when in the coastal ocean, and showed that they migrate north to the west coast of Vancouver Island in the fall [34]. A broader study using acoustic tags showed that Green Sturgeon make extensive seasonal migrations among spawning areas, over-summering in various estuaries and bays, and overwintering areas in the coastal ocean, with many individuals using areas around northern Vancouver Island [35], [36]. Further PAT work, using longer tag deployments, also showed this seasonal migration pattern, and fairly constrained depth and temperature distributions during the winter. Acoustic tags also revealed extensive use of and movement among non-natal estuaries. Green Sturgeon from different populations mixed together in common estuaries, but at different rates. Natal estuaries were used almost exclusively by fish from the associated natal river [36]. Green Sturgeon were also shown to have diverse patterns of migration within and among populations. Within the Sacramento River, acoustic tags revealed that a seasonal water diversion dam was a serious impediment to the spawning migration of Green Sturgeon [37]. Habitat data associated with tag detections was used to gain further insight into freshwater [38] and fine 2 [39] and coarse- scale [40] marine habitat preferences and seasonal patterns of distribution. Captive rearing of Green Sturgeon is providing important information on salinity tolerance and the timing for successful transition to marine waters, as well as optimal temperature for egg hatching, embryogenesis, and larval and juvenile survival [41–46]. In summary, the application of electronic tag technology to study Green Sturgeon revealed novel, reliable, and useful/relevant information regarding marine migrations and habitat use, spawning locations and periodicity, and both marine and freshwater life history attributes. While tagging revealed clear overall ...
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... and abundance, particularly for oceanic and nearshore phases of their life history. Almost all of the sturgeons that enter into saltwater have been understudied with respect to where they go and why (Table 1) and many endangered species have received relatively little scientific attention and study [9]. Researching these information gaps is extremely important for conservation of habitats and distinct populations. Here, we explore these issues while providing case studies and tools for examining movement and distribution of these ancient fishes. Sturgeons may move from one location or habitat type to another to feed, reproduce, or overwinter. River movement can be complex and include multi-step migrations [10] and include movement between and among rivers suggesting a meta-popula- tion structure [11]. Within a species, populations can differ on the timing of migrations into river systems, time spent within the river (holding), and the distance (upstream) from the marine environment where spawning occurs. Directed migrations from overwintering locations to feeding habitats, in some cases timed to intercept specific, localized prey species, may be a population- based behaviour; other populations of the same species may exhibit an entirely different food-related migration pattern based on the abundance/timing of localized prey. Protecting the genetic heritage and diversity of a species requires an understanding of these complexities at both the species and population levels, and an understanding of specific life-stage habitat requirements. Species and populations subject to harvest typically benefit from well-managed harvest regimes that incorporate respective migration information. There may be sex-specific differences in the timing of movements (often males arrive at the spawning grounds before females) so harvest/interception regimes may need to be sensitive to this in order to maintain the male:female sex-ratio balance within the population. Preserving the evolutionary potential of a species and its ability to respond to environmental change requires understanding the number of distinct populations within a species. Natal homing fidelity is thought to be strong and thus in many cases rivers, or sections of a watershed between natural barriers, often define populations. On the other hand, metapopulations may also exist [11]. If individual populations differ in terms of abundance and reproductive capacity, researchers and fishery managers may want to minimize mortality of individuals from certain river systems while they are in marine environments. Movement studies can provide the necessary information at both population and species levels and can provide the basis for protective schemes under national and international legislation. Characterizing environmental parameters that correlate with behaviour is further useful in evaluating the potential impact of habitat alteration (e.g. changes to the annual hydrograph of a sturgeon-bearing river). In some areas, introduction of non-native sturgeons and hybridization between species (e.g. Scaphirhynchus) due to habitat alteration and/or unintentional release from aquaculture (e.g. in Europe) makes understanding the movement and life history of introduced sturgeons or hybrid populations an important conservation consideration [12], [13]. Knowledge about movement and the spatial distribution of populations can also improve population assessments and help in specifying suitable management or recovery plans. Population assessments are still lacking for most species and are often hindered by an insufficient understanding of spatial distribution. Sturgeon species and/or populations with an anadromous life-history strategy may require assessment models that account for the seasonal movement patterns of different life-history stages exploited by fisheries [14], [15]. Tagging data can be incorporated into spatially explicit models to allow more accurate estimation of fishing mortality rates experienced by different age classes where fishing intensity varies by area [14], [16]. Insufficient data for parameterisation of models for migratory species with complex life histories can lead to large uncertainties in resource assessment and the likely effects of alternative management actions. The lack of data for key parameters of population dynamics has been identified as a contributor to the depleted and endangered status of many sturgeon populations throughout their range [17], [18]. Below, we present recent studies of the Gulf and Green Sturgeon to show how the information gained from these representative studies has been used to direct subsequent activities toward species conservation and the protection of key habitats. 1.2.1. Gulf Sturgeon. The anadromous Gulf Sturgeon, Acipenser oxyrinchus desotoi , a subspecies of the Atlantic Sturgeon, Acipenser oxyrinchus , occurs in most Gulf of Mexico river systems from the mouth of the Mississippi River to the west coast of Florida (Figure 2). Both mature and immature Gulf Sturgeon undergo freshwater migrations, typically entering coastal rivers in March or April and outmigrating to the ocean in September or October [19]. The cool-water period of estuarine or marine residency is critical for growth and reproduction, as Gulf Sturgeon do not feed during their freshwater residency. Early information about Gulf Sturgeon distribution and migration came primarily from commercial fishing [20]. Fishing operations in individual rivers were mostly short-lived (due to overharvest and subsequent fishery closures, as is typical for many in-river sturgeon fisheries), but the catches did provide some insights into the timing and extent of migration. More detailed information came from surveys in the 1980s conducted in response to declining catches and the species’ listing by the state of Florida as ‘‘threatened’’ [21], [22]. Marking with conventional tags mostly showed the range and extent of migration (e.g. recaptures of tagged fish by anglers below a dam or by commercial shrimp trawlers in Gulf of Mexico waters), whereas the first use of electronic tags (and manual/mobile tracking) provided insights about holding, staging, and spawning areas [22]; the use of radio tags in this study allowed the authors to characterize occupied riverine habitats in the Apalachicola River and to relate the timing of upstream and downstream migrations to environmental cues. Radio transmitters worked well for manual tracking of Gulf Sturgeon over long distances in rivers, but these transmitters cannot be detected in brackish or marine water. In the late 1980s a telemetry study was conducted wherein Gulf Sturgeon were tagged with both radio and sonic tags [23]. This was also the first Gulf Sturgeon study to use stationary receivers to detect and log passage events (in this case, to detect sonic tags as fish moved through barrier island passes [23]). The listing of Gulf Sturgeon in 1991 as a threatened species under the U. S. Endangered Species Act provided a further boost to research activity. For example, radio tracking studies in the Choctawhatchee River were initiated to identify potential spawn- ing sites, with confirmation through the use of artificial substrates to collect the adhesive eggs of Gulf Sturgeon [24]. Deployment of artificial substrates in a grid design provided fine-scale information about spawning habitat in the Suwannee River [25]. Marine habitat studies using sonic tags (and more recently, archival temperature-logging and pop-up archival tags) showed that Gulf Sturgeon sometimes moved long distances along the shoreline and primarily used shallow nearshore areas [26–29]. The fish occupying these marine habitats were often from multiple river systems; for example, [27] reported that Gulf Sturgeon from the Yellow, Choctawhatchee, and Apalachicola rivers were located within a 25-km stretch of coastline (eastern winter concentration area shown on Figure 2). The co-occurrence of Gulf Sturgeon from the Pearl and Pascagoula rivers has been documented [29] in the concentration area off Mississippi (western area shown on Figure 2). Thus, marine and estuarine threats and management efforts may affect more than one population. Genetic studies have also aided in understanding Gulf Sturgeon migration patterns. For example, it has been shown that within a basin, genetic structure exists at least at the drainage level and possibly at the level of tributary rivers within the basin [30]. The genetic analyses were helpful in interpreting telemetry results since some fish were tagged outside their natal drainage and others were captured or detected in multiple drainages. These research results formed the basis for the Gulf Sturgeon recovery plan and led to the designation of critical habitats. These important habitats included upper-basin spawning sites with limestone bluffs and outcroppings, estuarine and marine feeding sites with preferred substrates and benthic fauna, and summer resting areas. Genetic results showed strong natal river fidelity, so critical habitat was defined in each of the seven river systems containing currently reproducing populations (Pearl, Pascagoula, Escambia, Yellow/Blackwater, Choctawhatchee, Apalachicola, and Suwannee). This resulted in designation of nearly 2,800 river km as critical habitat for conservation of the species. 1.2.2. Green Sturgeon. In contrast to the relatively well- studied Gulf Sturgeon, the North American Green Sturgeon was little studied until 2002, when the US National Marine Fisheries Service received a petition to list it under the US Endangered Species Act. A severe lack of demographic and basic life-history information hampered the subsequent status review [31]. A particularly troubling unknown was the population origin(s) of Green Sturgeon that form dense aggregations in certain estuaries during summer months. Green Sturgeon were known to use just three rivers for spawning (the Sacramento and Klamath rivers ...

Citations

... Migratory fish management is often limited by a lack of information about how environmental variability and management actions intersect with natural complexity in habitat use, movements, and population status of a species (Nelson et al., 2013). This knowledge gap is largely due to the difficulty in reconstructing spatial distributions and habitat associations throughout individuals' lifespans, especially for long-lived species that make large migrations between habitats (Grande et al., 2009;Blechschmidt et al., 2020). ...
... Sturgeons (Acipenseridae) are ancient chondrostean fishes that inhabit aquatic environments throughout the Northern Hemisphere (Birstein et al., 1997;Nelson et al., 2013). Individuals may live over 100 years, mature as late as age 20-25, and reproduce infrequently (Billard and Lecointre, 2001). ...
... While White Sturgeon have experienced marked declines over the past century, they continue to support an important recreational fishery throughout the west coast of North America (Moyle et al., 2015;National Marine Fisheries Service [NMFS], 2015). Thus, identifying key environmental stressors and how they intersect spatially or temporally with sturgeon life histories remains a key priority for resource managers (Nelson et al., 2013). ...
Article
Full-text available
Understanding life-history diversity in a population is imperative to developing effective fisheries management and conservation practices, particularly in degraded environments with high environmental variability. Here, we examined variation in habitat use and migration patterns of White Sturgeon (Acipenser transmontanus), a long-lived migratory fish that is native to the San Francisco Estuary, CA, United States. Annual increment profiles were combined with respective geochemical (87Sr/86Sr) profiles in sturgeon fin rays to reconstruct annual salinity chronologies for 112 individuals from 5 to 30 years old. Results indicated a complex and diverse amphidromous life history across individuals, characterized largely by estuarine residence, a general ontogenetic trend toward higher-salinity brackish habitats, and high variability in habitat use across all age groups. Hierarchical clustering based on fin ray geochemistry during the first 10 years of life, prior to sexual maturation, indicated at least four distinct migratory phenotypes which differed largely in the timing and duration of juvenile to subadult movements between fresh- and brackish-water habitats. This study provides information regarding habitat use and migration in sub-adult fish that was previously lacking. Different migratory phenotypes vary in exposure to stressors across time and space and populations. Understanding White Sturgeon habitat distributions through space and time at different life stages can help identify areas where habitat restoration would be most effective and develop management actions to reduce stressors associated with specific areas where White Sturgeon are present.
... Finally, tagging studies can be useful to engage the public in research and raise awareness about the conservation status of a species (Nelson et al., 2013). Fish population monitoring and assessment programs in which people capture fish, report the presence of tags, apply tags to untagged fish, and collect basic information (e.g., fish length, location, date of capture) have proved to be successful (e.g., Comité ZIP du lac Saint-Pierre, 2008;Fortin et al., 1993). ...
... Acoustic telemetry (Bangley et al., 2020) and archival tags, like pop-up satellite archival tags, would provide a more complete picture of seasonal movement, migration patterns, and habitat selection (Erickson et al., 2011;Rothermel et al., 2020;Taylor et al., 2016). Because many of these advanced techniques require expensive equipment and specialized training, collaborative research involving multiple organizations and a variety of tagging techniques is likely the best approach for future studies on sturgeon movement at multiple temporal and spatial scales (Nelson et al., 2013). ...
Article
Movement of Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) and lake sturgeon (A. fulvescens) in the St. Lawrence Estuary (Québec, Canada) are not fully understood. To assess the movement extent of both species, a mark–recapture study was conducted in collaboration with commercial fishermen operating in the St. Lawrence Estuary. Between 1981 and 2015, 3,367 Atlantic sturgeon (fork length 21.8–199.5 cm) and 3,180 lake sturgeon (fork length 17.8–190.8 cm) were tagged and released. Of these, 673 Atlantic sturgeon and 42 lake sturgeon were recaptured. The maximum distances traveled between capture and recapture locations were 1,307 km for Atlantic sturgeon (8 years after initial capture) and 252 km for lake sturgeon (less than 1 year after initial capture). Statistical analyses identified differences in the dispersal distance of both species as revealed by a first component characterized by individuals with short dispersal distances (98% and <35 km for Atlantic sturgeon; 58% and <1 km for lake sturgeon) and a second component characterized by individuals with longer dispersal distances (2% and >600 km for Atlantic sturgeon; 42% and >190 km for lake sturgeon). We suggest that the short dispersal distances detected in the vast majority of Atlantic sturgeon recaptures likely reflect strong site fidelity, highlighting the importance of the St. Lawrence Estuary as a preferred habitat for juveniles and subadults. Although recaptures were low for lake sturgeon because this species is only marginally targeted by commercial fishermen in the St. Lawrence Estuary, our results also showed that this species uses estuarine habitats and that half of the population seems to exhibit strong site fidelity (67% of individuals were recaptured within 2 km).
... Genetic information can help determine connectivity between individuals and populations, and provides critical information about life cycles and life histories, movement patterns, sex-specific contributions and reproductive systems at the individual, species and community levels (Broquet & Petit, 2009;Fraser, Lippe, & Bernatchez, 2004;Nelson et al., 2013;Rooker et al., 2007). Genetic approaches used in the LMB to study population structure have shown that closely related species can exhibit very different population structures, suggesting differences in migration patterns. ...
Article
Full-text available
Despite their economic and ecological importance, migratory fishes of the Lower Mekong Basin (LMB) remain understudied, which hampers effective management to sustain valuable fisheries and address serious threats such as habitat degradation, development and overharvest. From a list of potential knowledge needs, a group of fisheries professionals most frequently identified six top priorities for managing migratory fishes in Cambodia: (1) population abundances and trends, (2) life cycles and life history, (3) migration timing and triggers, (4) migration routes and distances, (5) locations of key habitats and spawning areas, and (6) environmental and habitat requirements. These needs are discussed along with nine relevant methodologies for addressing them, including fisheries-dependent and fisheries-independent sampling, reproductive techniques and captive studies, otolith and genetic analysis tools, and tagging and imaging techniques. A suggested research framework is also presented to inform adaptive management of migratory fishes. While emphasis is given to Cambodia, the analysis is also applicable to other LMB countries, given that migratory fishes occur throughout the basin and migrate across borders. It is suggested that a robust research and monitoring agenda is required to prioritise knowledge needs and select appropriate methodologies to answer questions vital to inform sustainable migratory fish management in Cambodia.
... Worldwide there are approximately two dozen species of sturgeon; many exhibit a migratory life history that involves periodic long-distance movements in large river systems (Nelson et al., 2013). ...
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Dams can impede access to habitats that are required for the completion of life history phases of many migratory fish species, including anadromous sturgeons. Various forms of fish passage have been developed to permit migratory fishes to move above dams, but many dams still lack such structures. Translocation of ripe, mature fish above dams has been used as a first step to determine the efficacy of potential fish passage systems. The anadromous Gulf sturgeon, Acipenser oxyrinchus desotoi, inhabits the Gulf of Mexico and coastal rivers from Florida to Louisiana, and requires upriver spawning habitats to complete its life cycle. Historic overfishing and other anthropogenic threats, including dam construction, led to species declines and subsequent listing as threatened under the Endangered Species Act. In the Apalachicola River, FL, the 1957 completion of Jim Woodruff Lock and Dam (JWLD) created Lake Seminole and blocked Gulf Sturgeon from accessing 78% of historic riverine habitat—including potential spawning habitat—in the Apalachicola‐Chattahoochee‐Flint River Basin. The objective of this pilot study was to determine the efficacy of passage around JWLD through the trap‐and‐transport of 10 male Gulf sturgeon from the Apalachicola River to the reservoir above the dam. Through the use of acoustic telemetry, we were able to assess the ability of these fish to navigate Lake Seminole, access potentially suitable spawning habitat in the Flint and River, and complete their seasonal outmigration to the Gulf of Mexico. In this study, 2 translocated sturgeon moved 69 km upstream into potential spawning habitat in the Flint River, but 6 fish fell back through the lock/spill gates at JWLD within days of translocation. Four sturgeon appeared to remain trapped in the reservoir, and their long‐term survival was deemed unlikely. Given our low sample size, and examination of male fish only, we cannot conclude that a trap‐and‐transport program would ultimately fail to restore spawning above JWLD, but our findings suggest that the risk of adult mortality is nontrivial. Alternatively, we suggest future studies examine the population level trade‐offs associated with translocation of adults or consider alternatives such as a head‐start program to rear and release juvenile sturgeon above JWLD to study viability of their passage in addition to effects on overall recruitment in the population.
... Previous California White Sturgeon studies have used electronic tag, video, and rotary screw trap monitoring, and disc tag recapture in recreational fishery creel surveys to infer migratory patterns and spatial distributions (Nelson et al. 2013;Faukner and Jackson 2014;Klimley et al. 2015;Jackson et al. 2016;Mytton et al. 2018;Miller et al. 2020). Although this research has provided key insights, many questions remain about this species' life history diversity, habitat use, migratory patterns, and potential exposure to environmental contaminants. ...
... Previous California White Sturgeon studies have used electronic tag, video, and rotary screw trap monitoring, and disc tag recapture in recreational fishery creel surveys to infer migratory patterns and spatial distributions (Nelson et al. 2013;Faukner and Jackson 2014;Klimley et al. 2015;Jackson et al. 2016;Mytton et al. 2018;Miller et al. 2020). Although this research has provided key insights, many questions remain about this species' life history diversity, habitat use, migratory patterns, and potential exposure to environmental contaminants. ...
... Although this research has provided key insights, many questions remain about this species' life history diversity, habitat use, migratory patterns, and potential exposure to environmental contaminants. There are currently no long-term monitoring efforts for early White Sturgeon life stages in the SFE and its tributaries, and the spatially and temporally limited monitoring studies that have been conducted to date have uncertain application for understanding early life stage habitat use in long-lived species (Stevens and Miller 1970;Nelson et al. 2013). ...
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White Sturgeon (Acipenser transmontanus) are a long-lived, slow-growing, and late-reproducing anadromous fish common in estuaries and coastal habitats along the North American West Coast. These life history characteristics make populations vulnerable to human impacts and a challenge to study and manage. Previous studies in the San Francisco Estuary, California have provided insights into rearing habitats and migratory patterns but are limited in spatial and temporal scope. Fin ray geochemical analysis can provide a non-lethal approach to reconstruct migratory patterns and environmental conditions experienced throughout an individual fish’s lifespan. However, it is not known how soon post hatch age-0 White Sturgeon fin rays begin to calcify, reducing confidence in early life history temporal resolution using geochemical approaches. We used osteological (clear and stain) and geochemical techniques (laser-ablation-ICP-MS) to describe calcification initiation and completion, and element incorporation in the leading fin ray of known-age White Sturgeon reared at constant water temperature (18.6 °C) from 1 to 76 days post hatch (dph). We found that fin rays begin calcifying as early as ~20 dph (~27 mm total length) and are >95% calcified by ~72 dph (~70 mm total length). Consequently, the first ~20 dph are not likely to be recorded in the fin ray. Observed element (Li, Mg, Cu, Zn, Rb, Sr, Ba, Pb, U) incorporation patterns suggest that fin rays can provide a powerful tool to study White Sturgeon early movement and migratory patterns, habitat use, and environmental exposure.
... However, developing guidelines to conserve behavioral diversity is difficult because variation at the individual level is infrequently studied despite recognition that habitat use of mobile species is unlikely to fit a generalist pattern (Fodrie et al. 2015, Dwyer et al. 2019. For wide-ranging and long-lived species, the need to observe movements of individuals at biologically relevant spatial and temporal scales increases this difficulty even further (Nelson et al. 2013). Conservation programs that monitor and quantify variable habitat use among individuals can yield data to formulate management goals to conserve or even enhance population diversity and ultimately promote the long-term persistence of populations. ...
... Sturgeon (order Acipenseriformes) habitat use has been identified as among the least well known for fishes of conservation concern due to their long life spans, intermittent reproductive cycles, and large-scale movements between open-water habitats and spawning rivers (Nelson et al. 2013). Presumed fidelity to rivers where spawning occurs has resulted in sturgeon being classified for management purposes into population segments delineated by spawning rivers (e.g., Adams et al. 2007, Lindley et al. 2008. ...
... However, less is known about sturgeon habitat use outside spawning periods during which time they are thought to be widely distributed and individuals from different populations may overlap spatially (Erickson and Hightower 2007, Huff et al. 2012, Wirgin et al. 2015. Studies of sturgeon habitat use have largely focused on the 16 species with marine phases, but the nine freshwater species face similar conservation challenges as those using marine habitats (Gessner et al. 2013, Nelson et al. 2013. ...
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Understanding the spatial ecology of sturgeon (Acipenseridae) has proven to be a challenge due to the life history characteristics of these fish, especially their long life span, intermittent spawning, and long‐distance migrations. Within the Huron‐Erie Corridor (HEC) of the Laurentian Great Lakes, habitat use of 247 lake sturgeon (Acipenser fulvescens) was monitored over a three‐year period (2015–2017) with acoustic transmitters. Extensive spatial coverage of receivers throughout the St. Clair River, Lake St. Clair, and Detroit River between Lake Huron and Lake Erie (~150 km) allowed for continuous monitoring of the movements of acoustic‐tagged individuals. Sequence analysis of individual detection histories was used to describe lake sturgeon habitat use and to determine (1) whether distinct habitat‐use patterns occurred within the HEC; (2) whether the range of habitats occupied varied across seasons among sturgeon grouped by common patterns; and (3) whether variation identified was related to tagging sites in the two rivers or sex. Lake sturgeon were active throughout the HEC, but five distinct habitat‐use patterns were identified. River residents were not broadly distributed across entire rivers, but rather associated with particular segments (middle Detroit River, St. Clair River delta). Variations in habitat‐use sequences were in part related to three river tagging sites, but not sex, and did not produce groups with sequences that reflected all five habitat‐use patterns derived from cluster analysis. Lake sturgeon distribution was reduced to fewer habitat segments during winter and expanded to the maximum extent during the spring and summer. Conservation planning that incorporates behavioral diversity of habitat use is relatively rare due to a lack of observations on movements of individuals at biologically relevant spatial and temporal scales, but using telemetry and sequence analysis methods may promote the success of conservation and restoration efforts.
... According to the IUCN Red List of Threatened Species, only two out of 25 species in the family Acipenseridae have the status of least concern. Whereas 16 species are critically endangered, two are considered DOI: 10.3750/AIEP/02557 endangered, three species are vulnerable, and two species are considered near threatened (Nelson et al. 2013). ...
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Background. Recent genetic analyses of fish remains, obtained from archaeological sites, revealed that more than 2000 years ago the Baltic Sea was inhabited by sturgeons closely related to the Atlantic sturgeon, Acipenser oxyrinchus Mitchill, 1815. As some wildlife populations of the Atlantic sturgeon are still present in Canadian rivers, we decided to use those fish to restore the extinct Baltic population. Materials and methods. Fin clips of 50 A. oxyrinchus were collected from fry representing two hatcheries. At the hatchery No. 1 sturgeons were reared from fertilized eggs received from the Acadian Sturgeon and Caviar Inc., Canada. At the hatchery No. 2, larvae provided by the Regional Research Institute for Agriculture and Fisheries (Germany) were reared for several months until they were released into rivers. The molecular data of 22 and 28 specimens from hatcheries No. 1 and No. 2, respectively, were compared with homological D-loop sequences and some microsatellite loci derived from two museum specimens of sturgeons from the Tadas Ivanauskas Museum of Zoology, Kaunas, Lithuania. Signs of possible introgressive hybridization between Acipenser sturio Linnaeus, 1758 and A. oxyrinchus in two museum specimens were checked by comparison of alleles at loci AoxD161, AoxD188, AoxD297, AoxD242, and AoxC30. A possible affinity of between sturgeons released in Lithuanian rivers in 2015 and samples representing hatcheries No. 1 and No. 2 was estimated based on multi-locus genotyping data using the Structure software, version 2.3.4. Results. The same D-loop haplotype H1 characteristic for the museum specimens (MK637525 and MK637526) was also found as the only haplotype distributed among sturgeons reared in hatcheries and used for population re-establishment. A possible hybridisation between A. sturio and A. oxyrinchus was not confirmed for two museum specimens studied. The first results of genetic application undertaken in Lithuania also revealed the possibility to discriminate the individuals obtained from different hatcheries based on the set of 13 microsatellite loci Aox45, AoxD54, AoxD161, AoxD297, AoxD188, AoxD234, AoxD242, AoxC45, AoxC30, AoxD241, AoxD64, AoxD186, and Ls-68. The analysis of A. oxyrinchus specimens representing F1 generation of parental individuals reared in two separate hatcheries in Canada and Germany revealed significant differences in the allele composition and high probabilities for individuals released into the natural environment to be assigned to the hatchery of their origin. Conclusion. The results of the molecular analysis will be useful for identification of age, pedigree, and for initiating genetic monitoring of the restored population of the Atlantic sturgeon in the Baltic Sea.
... Early in the 20 th century, sturgeon research focused on fisheries, biology and taxonomy, but recent studies have focused on aquaculture and conservation because of the worldwide decline in sturgeon populations (Billard and Lecointre, 2000). There have been extensive literature surveys and reviews on sturgeon (Ludwig, 2006;Jaric and Gessner, 2012;LeBreton et al., 2006;Nelson et al., 2013). Slow growth and maturation, as well as extended spawning periodicity (i.e. ...
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The rapid decline in sturgeon populations is largely a result of human activities, especially the proliferation of hydraulic structures and lack of fish passage systems effective for sturgeon. This review highlights: (1) the importance of sturgeon conservation; (2) the need for data on swimming performance, including capability, metabolism and kinematics; (3) the relevance and limitations of swimming performance data in designing fish passage systems; (4) the need for experiments to develop sturgeon fishways that better reflect natural conditions. A proper understanding of swimming performance is crucial for designing effective fish passage systems. Although swimming performance and fish passage have been investigated for decades, knowledge and results have been limited by biological, methodological and analytical restrictions. To continue advancing passage effectiveness, continued research is necessary on sturgeon swimming performance and its interface with complex fishway hydraulics.
... Sturgeons are highly valuable species because of the increasing demand for their roe, caviar. The sturgeon fishery was historically the most important fishery in the Caspian Sea, but unfortunately sturgeon populations have drastically declined over the past two decades and have now been classified as "critically endangered" by the International Union for Conservation of Nature [4].Persian sturgeon (Acipenser persicus), acommercially valuable and critically endangered fish species has been suffering considerable declines in wild populations [5].Rapid loss of this species over the last century has been associated with increasing anthropogenic pressures notably over-fishing, illegal fishing, habitat loss, pollution as well as inherent life history characteristics (long life span, late maturation, and infrequent spawning) [6,7,8]. ...
... Lacroix and McCurdy, 1996). These tags transmit signals that are detected by fixed or shipboard receivers (Nelson et al., 2013). Thorstad et al. (2004) and Økland et al. (2006) tracked Atlantic salmon smolts carrying acoustic tags while also measuring ocean currents, and combined the two types of measurements to calculate the smolts' swimming speeds and directions. ...
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This study examines the effect of environmental conditions and swimming behaviors on the movement of Atlantic salmon (Salmo salar) post-smolts (juveniles) in the Gulf of St. Lawrence (GSL) using an individual-based model (IBM). The IBM uses time-varying and three-dimensional currents and hydrogra- phy produced by an ocean circulation model combined with a numerical particle-tracking scheme where swimming behaviors can be specified. Various experiments are run using this IBM with the aim of gaining insight into the observed movements of post-smolts documented in a past field study. In that study, a post-smolt released from the Saint-Jean River on the north shore of the GSL in June 2010 was found to exit the GSL through the Strait of Belle Isle (SBI) to the northeast of the release area. Two other post- smolts, released later in June 2010, were detected near Anticosti Island (AI) to the southwest of the release area. The numerical results suggest that, for both the post-smolt(s) that moved to the SBI and towards AI, the ambient near-surface circulation patterns favored their movements. In the case of movement towards AI, the travel times simulated using the simulated circulation pattern and a variety of swimming behaviors agree well with observations. For movement towards the SBI, an efficient swimming strategy is necessary in addition to a favorable circulation pattern in order for simulated travel times to be similar to observations. This study suggests two successful strategies for movement towards the SBI: (a) swimming with currents in favorable directions and against currents in unfavorable directions, and (b) swimming towards a series of target locations that define a migration route. The possibility that Atlantic salmon post-smolts originating from rivers on the north shore of the GSL may sometimes be confined to the GSL instead of migrating to the open ocean is consistent with past observational studies.