scholarly journals Hard time to be parents? Sea urchin fishery shifts potential reproductive contribution of population onto the shoulders of the young adults

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3067 ◽  
Author(s):  
Barbara Loi ◽  
Ivan Guala ◽  
Rodrigo Pires da Silva ◽  
Gianni Brundu ◽  
Maura Baroli ◽  
...  
Keyword(s):  
High Pressure ◽  
Sea Urchin ◽  
Sea Urchins ◽  
Reproductive Potential ◽  
Low Pressure ◽  
Size Class ◽  
High Density ◽  
Pressure Zone ◽  
High Pressure Zone ◽  
Commercial Size

BackgroundIn Sardinia, as in other regions of the Mediterranean Sea, sustainable fisheries of the sea urchinParacentrotus lividushave become a necessity. At harvesting sites, the systematic removal of large individuals (diameter ≥ 50 mm) seriously compromises the biological and ecological functions of sea urchin populations. Specifically, in this study, we compared the reproductive potential of the populations from Mediterranean coastal areas which have different levels of sea urchin fishing pressure. The areas were located at Su Pallosu Bay, where pressure is high and Tavolara-Punta Coda Cavallo, a marine protected area where sea urchin harvesting is low.MethodsReproductive potential was estimated by calculating the gonadosomatic index (GSI) from June 2013 to May 2014 both for individuals of commercial size (diameter without spines, TD ≥ 50 mm) and the undersized ones with gonads (30 ≤ TD < 40 mm and 40 ≤ TD < 50 mm). Gamete output was calculated for the commercial-size class and the undersized individuals with fertile gonads (40 ≤ TD < 50 mm) in relation to their natural density (gamete output per m2).ResultsThe reproductive potential of populations was slightly different at the beginning of the sampling period but it progressed at different rates with an early spring spawning event in the high-pressure zone and two gamete depositions in early and late spring in the low-pressure zone. For each fertile size class, GSI values changed significantly during the year of our study and between the two zones. Although the multiple spawning events determined a two-fold higher total gamete output of population (popTGO) in the low-pressure zone, the population mean gamete output (popMGO) was similar in the two zones. In the high-pressure zone, the commercial-sized individuals represented approximatively 5% of the population, with almost all the individuals smaller than 60 mm producing an amount of gametes nearly three times lower than the undersized ones. Conversely, the high density of the undersized individuals released a similar amount of gametes to the commercial-size class in the low-pressure zone.DiscussionOverall, the lack of the commercial-size class in the high-pressure zone does not seem to be very alarming for the self-supporting capacity of the population, and the reproductive potential contribution seems to depend more on the total density of fertile sea urchins than on their size. However, since population survival in the high-pressure zone is supported by the high density of undersized sea urchins between 30 and 50 mm, management measures should be addressed to maintain these sizes and to shed light on the source of the larval supply.

scholarly journals Hard time to be parents? Sea urchin fishery shifts potential reproductive contribution of population onto the shoulders of the youngest

2016 ◽  
Author(s):  
Barbara Loi ◽  
Ivan Guala ◽  
Rodrigo Pires da Silva ◽  
Gianni Brundu ◽  
Maura Baroli ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Sea Urchins ◽  
Gonadosomatic Index ◽  
Reproductive Potential ◽  
Size Class ◽  
High Density ◽  
Similar Amount ◽  
Potential Contribution ◽  
Total Density ◽  
Commercial Size

Background. In Sardinia, as in other regions of the Mediterranean Sea, sustainable fisheries of the sea urchin Paracentrotus lividus have become a necessity. At harvesting sites, the systematic removal of large individuals (diameter ≥ 50 mm) seriously compromises the biological and ecological functions of sea urchin populations. Specifically, in this study, we compared the reproductive potential of the populations from two Mediterranean coastal sites which have different levels of protection. The sites were Su Pallosu, where fishing pressure is high (take zone) and at Tavolara-Punta Coda Cavallo Marine Protected Area (no-take zone) where the pressure is negligible. Methods. Reproductive potential was estimated by calculating Gonadosomatic Index (GSI) from June 2013 to May 2014 both for individuals of commercial size (diameter without spines, TD ≥ 50 mm) and the undersized ones with gonads (30 ≤ TD < 40 mm and 40 ≤ TD < 50 mm). Gamete Output was calculated for the commercial-size class and the undersized individuals with fertile gonads (40 ≤ TD < 50 mm) in relation to their natural density (Gamete Output per m2). Results. The reproductive potential of populations was slightly different at the beginning of the sampling period but it progressed at different rates with an early spring spawning event in the take zone and two gamete depositions in early and late spring in the no-take zone. For each fertile size class, GSI values changed significantly during the year of our study and between the two levels of protection. Although the multiple spawning events determined a two-fold higher total Gamete Output of population (popTGO) in the no-take zone, the population Mean Gamete Output (popMGO) was similar in the two zones. In the take zone, the commercial-sized individuals represented approximatively 5% of the population, with almost all the individuals smaller than 60 mm producing an amount of gametes nearly three times lower than the undersized ones. Conversely, the high density of the undersized individuals released a similar amount of gametes to the commercial-size class in the no-take zone. Discussion. Overall, the lack of the commercial-size class in the take zone does not seem to be very alarming for the self-supporting capacity of the population, and the reproductive potential contribution seems to depend more on the total density of fertile sea urchins than on their size. However, since population survival in the take zone is supported by the high density of undersized sea urchins between 30 and 50 mm, management measures should be addressed to maintain this size and to shed light on the source of the larval supply.

scholarly journals Hard time to be parents? Sea urchin fishery shifts potential reproductive contribution of population onto the shoulders of the youngest

2016 ◽  
Author(s):  
Barbara Loi ◽  
Ivan Guala ◽  
Rodrigo Pires da Silva ◽  
Gianni Brundu ◽  
Maura Baroli ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Sea Urchins ◽  
Gonadosomatic Index ◽  
Reproductive Potential ◽  
Size Class ◽  
High Density ◽  
Similar Amount ◽  
Potential Contribution ◽  
Total Density ◽  
Commercial Size

Background. In Sardinia, as in other regions of the Mediterranean Sea, sustainable fisheries of the sea urchin Paracentrotus lividus have become a necessity. At harvesting sites, the systematic removal of large individuals (diameter ≥ 50 mm) seriously compromises the biological and ecological functions of sea urchin populations. Specifically, in this study, we compared the reproductive potential of the populations from two Mediterranean coastal sites which have different levels of protection. The sites were Su Pallosu, where fishing pressure is high (take zone) and at Tavolara-Punta Coda Cavallo Marine Protected Area (no-take zone) where the pressure is negligible. Methods. Reproductive potential was estimated by calculating Gonadosomatic Index (GSI) from June 2013 to May 2014 both for individuals of commercial size (diameter without spines, TD ≥ 50 mm) and the undersized ones with gonads (30 ≤ TD < 40 mm and 40 ≤ TD < 50 mm). Gamete Output was calculated for the commercial-size class and the undersized individuals with fertile gonads (40 ≤ TD < 50 mm) in relation to their natural density (Gamete Output per m2). Results. The reproductive potential of populations was slightly different at the beginning of the sampling period but it progressed at different rates with an early spring spawning event in the take zone and two gamete depositions in early and late spring in the no-take zone. For each fertile size class, GSI values changed significantly during the year of our study and between the two levels of protection. Although the multiple spawning events determined a two-fold higher total Gamete Output of population (popTGO) in the no-take zone, the population Mean Gamete Output (popMGO) was similar in the two zones. In the take zone, the commercial-sized individuals represented approximatively 5% of the population, with almost all the individuals smaller than 60 mm producing an amount of gametes nearly three times lower than the undersized ones. Conversely, the high density of the undersized individuals released a similar amount of gametes to the commercial-size class in the no-take zone. Discussion. Overall, the lack of the commercial-size class in the take zone does not seem to be very alarming for the self-supporting capacity of the population, and the reproductive potential contribution seems to depend more on the total density of fertile sea urchins than on their size. However, since population survival in the take zone is supported by the high density of undersized sea urchins between 30 and 50 mm, management measures should be addressed to maintain this size and to shed light on the source of the larval supply.

A Probabilistic High-Pressure Zone Model for Local and Global Loads During Ice-Structure Interactions

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Rocky S. Taylor ◽  
Martin Richard ◽  
Ridwan Hossain
Keyword(s):  
High Pressure ◽  
Field Measurements ◽  
Zone Model ◽  
Probabilistic Framework ◽  
Local Pressure ◽  
Pressure Zone ◽  
Current Design ◽  
Ice Loads ◽  
High Pressure Zone ◽  
Ice Failure

For temperate ice regions, guidance provided by current design codes regarding ice load estimation for thin ice is unclear, particularly for local pressure estimation. This is in part due to the broader issue of having different recommended approaches for estimating local, global, and dynamic ice loads during level ice interactions with a given structure based on region, scenario type, and a variety of other conditions. It is essential from a design perspective that these three scenarios each be evaluated using appropriate definitions for local design areas, global interaction area, and other structural details. However, the need for use of different modeling approaches for ice loads associated with each of these scenarios is not based on ice mechanics but rather has largely evolved as a result of complexities in developing physics-based models of ice failure in combination with the need to achieve safe designs in the face of limited full-scale data and the need for implementation in a probabilistic framework that can be used for risk-based design assessments. During a given interaction, the ice is the same regardless of the design task at hand. In this paper, a new approach is proposed based on a probabilistic framework for modeling loads from individual high-pressure zones acting on local and global areas. The analysis presented herein considers the case of thin, first-year sea ice interacting with a bottom-founded structure based on an empirical high-pressure zone model derived from field measurements. Initial results indicate that this approach is promising for modeling local and global pressures.

scholarly journals OC42: Visualization of the vaginal high-pressure zone by three-dimensional ultrasound images in the pelvic floor

2006 ◽  
Vol 28 (4) ◽  
pp. 371-371
Author(s):  
S. A. Jung ◽  
D. H. Pretorius ◽  
B. S. Padda ◽  
M. M. Weinstein ◽  
C. W. Nager ◽  
...  
Keyword(s):  
High Pressure ◽  
Pelvic Floor ◽  
Three Dimensional ◽  
Ultrasound Images ◽  
Pressure Zone ◽  
High Pressure Zone

Tu1803 Dysphagia Post-Fundoplication Evaluated With High-Resolution Manometry (HRM). The Relevance of a Dual High-Pressure Zone

2013 ◽  
Vol 144 (5) ◽  
pp. S-850
Author(s):  
Etsuro Yazaki ◽  
Yu Tien Wang ◽  
Jafar Jafari ◽  
Asma Fikree ◽  
Nora Schaub ◽  
...  
Keyword(s):  
High Pressure ◽  
High Resolution ◽  
High Resolution Manometry ◽  
Pressure Zone ◽  
High Pressure Zone
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