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Wie viel ist genug? Wie viele Sklaven halten Sie? Wie wir lieben Wie wirklich ist die Wirklichkeit? Wikinomics Will It Fly? Log in to Blinkist. Log in Log in. You don't have an account? For example, a preliminary study by Sulikowski et al. The preliminary results suggested that these sharks did not make long distance migrations over the deployment period, but rather moved in an easterly direction towards offshore waters. Diel vertical movement patterns suggested that the sharks were highly active during both the day and night, spending a portion of time off-bottom and likely out of reach of the trawl survey nets.
The information from Sulikowski et al.
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These observations could, in part, start to explain some of the anomalies in the SSB estimates. Tag and release activities were conducted in federal waters and no specific agency permissions were required. The X-Tags weighed 40 g in air, measured mm in body length, mm in antenna length, and 32 mm in maximum diameter. These individuals were all caught off the University of New England's 7. An effort was made to deploy tags on an equal number of male and female spiny dogfish in each region.
While the dogfish used were not weighed individually, adult dogfish range in weight from 7. Sulikowski, pers. The X-Tags were affixed to each spiny dogfish by attaching a tether to the second dorsal fin spine. The entire attachment was encased in a 7. After 30 min, spiny dogfish deemed suitable for use in the study i. Temperature and depth data were recorded at 2-min intervals and were available at that resolution for tags which were physically recovered. For tags that were not physically recovered, lower resolution compressed data were recovered via satellite transmissions.
The data compression i. Resolution of data can be available at min increments for tag deployments up to four months , min increments four—eight month deployments or min increments eight—twelve month deployments. The X-Tag data compression programming for transmitted data also has limits on the rate of temperature and depth changes it can record.
Limits of X-Tag recorded depths are constrained to a change in descent between recordings of Changes in depth that exceeded these limits accounted for on average 0. Temperature records were not affected by delta-limited values. These limitations do not extend to data stored on the tag for those physically recovered. The X-Tags were also programmed with a constant depth sensor in the event the tag records a constant depth within 3 m for six days that tag would detach and start reporting to the satellite.
Thus, if the animal dies and sinks to the bottom or the tag detaches and floats at the surface for more than six days, the tag begins to transmit the archived data. Additionally, prior to attachment, X-Tags were tested for pop-up mechanism and satellite transmission, as according the manufacturer's instructions. Once these data were received, they were processed through a stepwise set of filters and analyses.
The preliminary estimated geolocations were fitted with a state space extended Kalman filter model kftrack in analyzepsat 3. In the event that the tag detached early, pop-up date was determined by signs of detachment in the temperature and depth data i. The most probable track was then bathymetrically corrected btrack in analyzepsat 3.
The bathymetric correction is particularly useful for estimating tracks based on limited light levels, few latitude estimates, and increased time at depths deeper than m, which occurred for the majority of tagged spiny dogfish. An additional sea-surface temperature filter ukfsst in analyzepsat 3. The geolocations resulting from the bathymetric correction were considered the most probable geolocations and were the positions used in all subsequent analysis. The bathymetrically corrected geolocation points were used to examine magnitude and direction of movements as well as habitat use.
To do so, the direction and magnitude between individual points were measured for each individual in both regions.
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The calculations were then summarized as circular histograms for each season and separated by region. The bathymetrically corrected points were also used to calculate kernel utilization distributions. These UDs were produced for each individual and binned groups, including the whole tag group inclusive of all sharks from both tagging sites , separate northern released tags only 19 successful northern tags , and southern released tags only 15 successful southern tags.
To look for possible migratory patterns, UDs were also calculated by season for both the northern and southern groups. Geolocation points results from bathymetric correction with CIs were compared to recreated maps of temporally appropriate NEFSC spring and autumn bottom-trawl survey sampling stations. These surveys begin off NC and work northward to the GOM following a stratified random design within different geographic strata  — .
These interpolations were then visually compared to tag geolocations to determine if any association of movement patterns or distribution existed seasonally for seasons in which the surveys occurred, spring and autumn and monthly for months in which the surveys occurred, which varied in both seasons from to  — .
Exact start and stop dates of the biannual surveys were used with exact geolocation timestamps to avoid under- or over-estimation. Areas of overlap between survey stations and geolocations including CIs were identified to determine the percentage of geolocations located within the temporally corresponding survey locations, as previously described, using only the stations and geolocations with the same timestamp.
Instances where the tag and trawl depth ranges overlapped were considered to be likely available to be captured. Depth and temperature data were evaluated on an individual and binned groupings basis, following the same scheme as the horizontal data. Overall differences between northern and southern temperature and depth data were tested for statistical significance using a t-test in SigmaPlot Systat Software, San Jose, CA. Seasonal temperature and depth and diel depth differences between the two groups were tested for statistical significance using a two-way Analysis of Variance ANOVA.
Days that did not have a full daily record 96 recordings at 15 min intervals, 48 recordings at 30 min intervals, or 24 recordings of 60 min intervals of temperature and depth were excluded when analyzing diel movement patterns. Diel depth was evaluated for the northern and southern groups overall, as well as seasonal differences between the groups. Diel depth patterns were assessed by calculating the difference between the depth at time of day and the daily mean depth for each individual spiny dogfish, then averaged by time of day for the two groups.
In addition, three tags from each deployment site were also physically recovered and returned for high-resolution data extraction. The geolocation points used in the subsequent analysis all represent daily locations, although the interval between points was variable between individuals depending on light levels collected by the tag. The smallest interval between geolocation points was one day, and the largest interval was 29 days.
The estimated daily geolocations Figure 1A and majority of known pop-up locations Figure 2A from the northern spiny dogfish revealed trends in movement patterns that appeared to be regionally centered.
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Conversely, the estimated daily geolocations Figure 1B and known pop-up locations Figure 2B for the southern spiny dogfish were more dispersed from the deployment site than the northern spiny dogfish, but do not extend into the GOM. Similar to the northern satellite tags, one southern spiny dogfish ID deviated from the group majority of geolocations. Two representative tracks one from each tagging group are shown in Figure 3 from individuals that retained their tags for days. When month specific geolocations for mature females in both regions were mapped, the majority of the geolocations were close to respective deployment sites either in the GOM or off NC with little overlap between the groups along the mid-coast Figure 4.
Seasonal circular histograms of individual movement by region suggests little to no distinct seasonal pattern in the northern geolocations, but stronger seasonal directionality for the majority of movement in the southern geolocations Figure 5. The southern individuals show strong northeastward spring and northwestward summer movement of greater magnitude than the northern individual movements for the same seasons eastward and northwestward majority movement respectively.
Autumn and winter movement for the southern spiny dogfish was not as strong in magnitude, however the majority of movement does suggest a southwestward autumn and northeastward winter movement tendency. While the northern autumn westward and southeastward and winter southeastward movements are of lesser magnitude compared to the southern spiny dogfish, the summary of data still suggest strong movements within the northern region.
Tag deployment sites are marked in the Gulf of Maine northern tags and off the coast of North Carolina southern tags. Each point represents one tag pop-up point. The numbers inside of the triangles represent the month in which the tag popped. The green circle represents the point of deployment for both the northern A and southern B tags.
The red points are the geolocations used to calculate the UDs. The black points are the geolocations used to calculate the UDs. Colors of points represent different months throughout the year.
Colors of points represent different months of proposed parturition. Northern UDs remained inshore east of the continental shelf break throughout all four seasons, expanding slightly more towards offshore west of the continental shelf break in autumn and winter. Utilization distributions for the southern group remained inshore in winter and spring and expanded further offshore than the northern group in summer and autumn. Plotting the NEFSC bottom-trawl survey stations with the temporally corresponding geolocations with CIs suggested spatial overlap horizontal availability to the surveys between the tagged sharks and the seasonal survey.
Results indicate only Seasonal vertical availability from the points that were horizontally available , to trawl depths yielded Monthly total availability fluctuated from 0— Autumn was the only season that showed spatial overlap between the northern group and southern group C. Analysis of vertical movement patterns indicated both the northern and southern spiny dogfish actively utilized a large portion of the water column. Differences in depth ranges for the two groups were observed with the northern group occupying waters from the surface 0 m to depths of The northern group primarily resided at an overall mean depth of Comparing the differences between hourly diel depths and mean daily depths suggests different diel patterns between the two groups, as the northern spiny dogfish displayed a more drastic change in depths from night and day than the southern spiny dogfish Figure 8.
The northern tags show a larger change in mean diel depths than the southern tags. Error bars represent standard error. The mean depths for the northern group ranged from Similarly, mean seasonal depths for the southern group were also different, though they were less variable than the northern group. Southern sharks utilized deeper depths during summer Analyses of temperature data revealed that although spiny dogfish tagged in the northern group exhibited a large range in temperature 2.
Similarly, the sharks from the southern group also exhibited a large overall temperature range 5. The northern sharks appeared to oscillate from the warmest temperatures in summer 9. More pronounced than the northern spiny dogfish, the southern sharks displayed a similar pattern with warmest temperatures in autumn Comparisons of temperatures obtained from satellite tagged spiny dogfish to spatiotemporally corresponding bottom temperatures obtained from NEFSC bottom-trawl data suggested divergent results.
Interpolated bottom temperatures gathered from the autumn surveys bottom temperatures 9. However, given the error around the estimated point geolocations, the general trends observed between the two tagging groups are intended to be indicative of only conservative, broad-scale movement patterns, as reported in other PSAT studies  , . When general movement patterns from the two groups were further modeled using aggregate geolocations and UDs these data provided a better overall sample-wide understanding than using individual track analyses. For instance, two-thirds of the geolocation points in each group were non-overlapping with geolocations from the opposing group , indicating an apparent separation in the northern and southern groups within the spiny dogfish's known centralized range.
Additionally, the two groups also had divergent movement patterns from one another, with the northern spiny dogfish staying more localized and less synchronous within the group, while the southern spiny dogfish were more widespread with more distinct synchronous oscillatory patterns. Despite the large, acknowledged error associated with these geolocation techniques  ,  , the present data suggests there were differences in overall movement between the two groups. The findings presented herein support previous movement patterns from satellite tagged spiny dogfish which observed restricted movement patterns in sharks tagged within the GOM  and previous TRAC Status Report findings, suggesting overall segregated spatial structuring between the northern and southern extents of their known range .
While other reports from bottom trawl surveys  —  and conventional tagging studies  ,  suggest broad-scale movement patterns and aggregations of spiny dogfish in the GOM during autumn and along the shelf off NC during spring, these findings were not supported by the data herein. This could possibly be explained by relatively low sample size compared to the U.
Due to the timing of the northern tagging events, we cannot rule out the possibility that some of the sharks tagged had already completely migrated north and thus stayed relatively close to the tagging site. The lack of variation in spatiotemporal events could also affect the apparent deficiency of northward movement if migrating individuals had already moved into the northern most extent of the seasonal migration pattern.
For example, if spiny dogfish had already left the tagging site area in the north i. A notable observation in the study was the segregation of the northern and southern groups of spiny dogfish. The same behavior has also been observed in salmon sharks  and spiny dogfish Squalus acanthias in the Pacific Ocean .
This resident and migrant behavior within a population has been observed in white sharks in Hawaii  and brown trout Salmo trutta in Norway . For instance, the bulk movement in autumn and winter northern group and summer and autumn southern group suggested divergence in aggregate geolocation, and convergence of geolocations for both groups overlapping in autumn. These separations within each group could indicate the parting of a breeding stock migratory individuals from both north and south , that congregate near Cape Cod in autumn, and a non-breeding stock resident individuals from each group that stays closer to respective deployment sites.
This same complex pattern of breeding and non-breeding stocks was observed in white sharks around Guadalupe Island, Mexico where a proposed two year migration pattern based off an month gestation was driven by a mating route year 1 and a non-mating route year 2 . The same population of white sharks in Mexico also exhibited analogous patterns of a primary area of seasonal overlap between two subpopulation groups  , suggestive of a possible site for prime foraging or mating  and similar to the patterns seen herein, based off of what is known about spiny dogfish gestation  —  ,  , .
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The reproductive mode of the spiny dogfish is characterized as yolk-dependent viviparity in which full embryonic development occurs within the uteri of the mother, and a yolk-sac provides the majority of the nourishment . Follicular maturation and gestation occur simultaneously in this species, once females reach sexual maturity . Although females were not assessed for reproductive status in the current study, all females were mature and assumed gravid . If indeed this is the case, geolocations of mature females during the proposed pupping season October—May support previous studies which suggest both inshore and offshore pupping areas exist for the US population  ,  —  ,  — .
However, due to the limitations above and the temporal difference between the two groups, further research needs to be conducted on how gestation period and movement patterns may be connected before any conclusions can be drawn. The majority of the satellite tags deployed in the northern region remained in coastal waters of the GOM during spring — , suggesting that not all spiny dogfish migrated southward, and were therefore not accounted for during those particular seasonal surveys.
This finding also contradicts previous documented movement patterns  —  , which suggest that spiny dogfish should be absent from the GOM during this time of year . Results of the current study demonstrate movement outside offshore of the NEFSC bottom-trawl survey area and a high degree of vertical activity, suggesting that spiny dogfish captured by bottom-trawls could represent a smaller proportion than previously thought, resulting in potentially underestimated biomasses  — .
It is possible that spatial constraints west of the continental shelf break, selective substrate types , a single gear type bottom-trawl , and temporal restrictions limited to two seasons per year, starting of the coast of NC and moving north to the GOM may in part, be responsible for the variability in the NEFSC survey biomass estimates relative to the true population of dogfish  — . In addition, vertical distributions of many species vary with time of day, affecting the availability of fish to demersal trawl gears .
Frazier et al.
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When a catchability coefficient was applied to North Sea bottom groundfish species, the catch correction suggested that raw trawl survey density data significantly underestimated actual densities . Based on this new information pertaining to spiny dogfish seasonal horizontal and vertical distribution and the results of Frazier et al. Pop-up archival satellite tags have expanded the knowledge of vertical and thermal habitat preference previously unknown for spiny dogfish and other species. The behavior observed in the current study suggests that spiny dogfish vertical activity is not representative of a predominantly benthic species  —  , and that this species actively uses the majority of the water column throughout the day, corroborating the findings of Sulikowski et al.
Similarly, satellite tags have revealed behavioral patterns in immature Greenland sharks Somniosus microcephalus ,suggesting this species spends a considerable amount of time off the bottom and depth preferences appear to be similar to a more pelagic shark species . In other species, previously undocumented vertical utilization of tagged juvenile Atlantic bluefin tuna Thunnus thynnus was observed in the northwest Atlantic Ocean, providing valuable insight for assessing stock structure and fisheries plans . In the current study, the mean depth utilized by the southern group However, since sharks within the southern group traveled further off the continental shelf and into much deeper water than the northern group, the data herein would suggest the southern group was not constrained to shallow water, but possibly seeking a preferred depth.
Overall vertical activity peaked in different seasons for the northern summer and southern winter groups. Within this high amount of vertical activity, the observed seasonal mean depths between the two groups suggest non-synchronous cyclic patterns in depths utilized. The two groups were closest to each other during autumn, with a mean depth of Similar to Sulikowski et al. This pattern of vertical movement has been observed in other elasmobranch species such as white sharks  , scalloped hammerheads, Sphyrna lewini  , sixgill sharks Hexanchus griseus  , bigeye threshers Alopias superciliosus  , and basking sharks Cetorhinus maximus  , where the pattern has been linked to prey searching or locating optimal temperature and oxygen conditions  — .
While the reasons behind the observed patterns cannot be elucidated from the current study, similar behavioral patterns have been observed in other species. For example, blue sharks  , bluefin tuna  , shovel-nose guitarfish  and leopard sharks  are thought to seek out ideal temperatures or relatively small temperature ranges to optimize daily metabolic and foraging requirements. In addition to the prevalence for seeking an optimal temperature, the differences in mean temperatures between the northern and southern groups corroborate the segregated horizontal movement patterns observed in the current study.
This type of pattern is supported by Fisk et al. This phenomenon has been observed in a number of species in the U. The information obtained in the current study from satellite tagged sharks appeared to have reduced some of the uncertainties associated with spiny dogfish vertical and horizontal movement, while also providing insight into the potential availability of this species in NEFSC bottom-trawl surveys  , . Several factors can affect the likelihood of availability in a bottom-trawl survey, including the uncertainty of horizontal migration patterns, environmental influences, and degree of vertical activity of the target species  , .
However, the overall low total availability of spiny dogfish highest estimate Regardless, the availability results presented herein suggest a large portion of the spiny dogfish population is most likely not sampled on an annual basis in the NEFSC bottom-trawl survey. The observed differences between the two tagging groups of spiny dogfish on the U. Further investigations are needed to address the observed differences in habitat utilization, availability and stock structure to determine the degree of segregation, and possible additional subpopulations or metapopulations, between the northern and southern spiny dogfish and to augment future management plans.
This manuscript represents MSC contribution number Conceived and designed the experiments: JS. Performed the experiments: AC JS. Analyzed the data: AC. Completed fieldwork: AC JS. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field.
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