scholarly journals Assessment of size selectivity in hydraulic clam dredge fisheries

2017 ◽  
Vol 74 (3) ◽  
pp. 339-348 ◽  
Author(s):  
Antonello Sala ◽  
Jure Brčić ◽  
Bent Herrmann ◽  
Alessandro Lucchetti ◽  
Massimo Virgili

In hydraulic dredge clam fisheries, the onboard mechanical sorting can be considered as the main catch selection process. The catch is mechanically sorted by a sieve made up of a series of successive grids with holes of decreasing diameter. The effect of the grid hole diameter and sorting speed of the vibrating sieve of a hydraulic dredger was investigated in a field study to determine its clam selection properties and to formulate proposals aimed at improving fishery management. Data analysis demonstrates that it is technically impossible to achieve a knife-edge selection and that there is scope for improving the size selection process, for instance by increasing grid hole diameter, which, however, can be accompanied by a reduced catch of both undersized and commercial-sized individuals. An increase in the hole diameter to 21.71 mm, while ensuring less than 5% retention of undersized individuals, would entail a retention of 67% of the commercial sizes. The modelling approach applied can be extended to investigations of other dredge gear types and nonmobile benthic species.

2018 ◽  
Vol 75 (5) ◽  
pp. 1693-1709 ◽  
Author(s):  
Chryssi Mytilineou ◽  
Bent Herrmann ◽  
Danai Mantopoulou-Palouka ◽  
Antonello Sala ◽  
Persefoni Megalofonou

Abstract Gear selectivity and discards are important issues related to fisheries management but separately modelled. This work examines for the first time the overall size-selection pattern on the total amount of individuals of a species entering the trawl codend. An innovative approach was used based on modelling the escapement through the codend in the sea and the subsequently selection process by the fisher on the deck of the fishing vessel resulting into the discards and landings. Three different trawl codends and three species were investigated in the case study conducted. A dual sequential model accounting for both gear size-selectivity and the subsequent fisher-size-selectivity was applied, under the hypothesis that a fish entering the codend can follow a multinomial distribution with three probabilities, the escape, the discard and the landing probability, respectively. The model described the escape probability through the gear and the landing probability by the fisher as S-shaped curves leading to a bell-shaped curve for the discard probability affected by both gear and fisher selection. The model described well the experimental data in all cases. Sampling scheme of three compartments proved adequate. The model provides at the same time selectivity and discards parameters useful in fisheries management.


2019 ◽  
Vol 76 (8) ◽  
pp. 1350-1361 ◽  
Author(s):  
Bent Herrmann ◽  
Manu Sistiaga ◽  
Eduardo Grimaldo ◽  
Roger B. Larsen ◽  
Leonore Olsen ◽  
...  

Size selectivity of a new sorting section combining a sorting grid and a square mesh panel was tested for haddock (Melanogrammus aeglefinus) in the Barents Sea demersal trawl fishery. Sampling data for a wide size range enabled investigating the selection process for this species in detail, both for the grid and the square mesh panel. Contrary to earlier studies modelling size selectivity for grids and square mesh panels, which assume that the escape behaviour of all sizes of fish is equal, we applied a model that accounted for haddock of different sizes showing different escape behaviours. Our results demonstrated that this model could describe the experimental data collected better than existing models. Specifically, our results showed that the likelihood for smaller haddock to seek escape through the grid and the square mesh panel was higher than that for bigger haddock that still would manage to escape through the devices if they attempted. The new modelling approach presented in this study may be applicable to other species, selection devices, and fisheries.


Author(s):  
Martin Bettschart ◽  
Marcel Herrmann ◽  
Benjamin M. Wolf ◽  
Veronika Brandstätter

Abstract. Explicit motives are well-studied in the field of personality and motivation psychology. However, the statistical overlap of different explicit motive measures is only moderate. As a consequence, the Unified Motive Scales (UMS; Schönbrodt & Gerstenberg, 2012 ) were developed to improve the measurement of explicit motives. The present longitudinal field study examined the predictive validity of the UMS achievement motive subscale. Applicants of a police department ( n = 168, Mage = 25.11, 53 females and 115 males) completed the UMS and their performance in the selection process was assessed. As expected, UMS achievement predicted success in the selection process. The findings provide first evidence for the predictive validity of UMS achievement in an applied setting.


Author(s):  
Yune Andryani Pinem

This research looks at listening as one factor that gives contribution toward speaking among high school students. The study attempts to reveal through data analysis, in the form of students. score from each variable that both have correlation. Further the objective of the study is also to find out the extent of influence contributed by listening toward speaking. The research applies library study and field study (instrument designing and test performing both for listening and speaking). The theory used for analysis deals with listening and speaking correlation from language learning review. The result of the study demonstrates that the correlation of listening as the independent variable with speaking as dependent variable is positive. It also proves that with a unit of program or treatment given toward listening class, there will be a significant improvement equals with 3.134 times from previous speaking score for the same sample. For the analysis of data, the extent of correlation between two varibales is shown as low. It indicates that even though listening do have positive correlation towarde speaking, it is not the only deminant factor to determine success in speaking.


2021 ◽  
Vol 16 (1) ◽  
pp. 96-120
Author(s):  
Lazuardi muhammad Latif ◽  
Faisal Bin Ahmad Shah

Wasl al-Fiqh bi al-Hadith integrates jurisprudence and hadith so that it enables fiqh experts to rely on hadith in formulating their rulings while hadith experts can derive a more accurate interpretation. Among others, this concept is applied at Aceh traditional dayah as the oldest Islamic educational institution in the Malay Archipelago which Acehness put their respect as the reference in Islamic rulings and teaching. This field study took place at Dayah Mudi Mesra, Samalanga, Aceh, due to its long-established reputation and great influence among Acehnese. The study aims to shed some light on the concept of wasl al-Fiqh bi al-Hadith according to some Islamic scholars, analyze the concept as perceived by the traditional Dayah of Aceh, and portray the polemic on Friday prayer ritual as prescribed by the traditional Dayah. The study employs qualitative data collection instruments consisting of library data, interviews, observations, and documentation. Inductive, deductive, and comparative methods were used for data analysis. The study found that implementation of this concept at the Dayah has been synonymous with the exclusive adoption of Shafi’i school as it heavily relies on several Shafi’i books or opinions of Shafi’i scholars as primary references.(Wasl al-Fiqh bi al-Hadith memadukan kajian fiqh dan hadis sehingga ahli fiqh dapat berpedoman kepada hadis dalam merumuskan aturan-aturan hukum sementara ahli hadis dapat mengetahui makna sebuah hadis dengan lebih akurat. Konsep ini salah satunya diterapkan di Dayah Tradisional Aceh, sebuah lembaga kajian Islam tertua di Kepulauan Melayu yang disegani dan menjadi rujukan dalam hal aturan serta ajaran Islam di masyarakat setempat. Kajian ini merupakan studi lapangan yang bertempat di Dayah Mudi Mesra Samalanga Aceh karena pengaruhnya yang sudah lama dan berakar kuat bagi masyarakat Aceh. Ia bertujuan mendalami konsep wasl al-fiqh bi al-hadith menurut para cendekiawan Muslim, mengkaji pemahaman akan konsep wasl al-fiqh bi al-hadith di kalangan Dayah tersebut dan memotret polemik soal pelaksanaan Salat Jumat di dalamnya. Kajian ini merupakan studi kualitatif dengan pengumpulan data secara pustaka, wawancara, observasi, dan dokumentasi. Sementara itu, analisis data dilakukan secara induktif, deduktif, dan komparatif. Hasil penelitian ini menunjukkan bahwa implementasi konsep tersebut sebenarnya tidak lebih dari adopsi eksklusif terhadap madzhab Syafi’i karena ketergantungan yang demikian kuat pada buku-buku madzhab Syafi’i serta pandangan ulama-ulama Syafi’iyyah sebagai referensi utama)


2020 ◽  
Vol 77 (2) ◽  
pp. 425-437
Author(s):  
Daniel C. Gwinn ◽  
Gavin Butler ◽  
Brett Ingram ◽  
Scott Raymond ◽  
Mark Lintermans ◽  
...  

Estimating the size selectivity of fishery users and sampling methods can be difficult to achieve due to data limitations. However, these limitations can be moderated by borrowed information from other sources such as other systems, times, and species. Here we develop a model that integrates an externally sourced boat electrofishing length–vulnerability model with internally sourced boat electrofishing and angling catch data to estimate length-dependent vulnerability of fish to angling in a data-limited situation. We apply the model to Murray cod (Maccullochella peelii) as an example and show that angling for Murray cod selectively captures a narrow range of sizes that includes medium to large size fish. Although boat electrofishing also followed a similar pattern, the range of fish sizes vulnerable to capture was much broader, including a more uniform vulnerability of all size classes evaluated. Understanding the length selectivity to capture has key implications for effective determination of fisheries regulations, as well as interpreting monitoring data. Thus, we see this modelling approach as a good option when more informative data are not available to support the estimation process.


Author(s):  
Imam Muttaqin ◽  
Cokorda Gede Alit Semarajaya ◽  
Lury Sevita Yusiana

Camping ground planning of Alun-alun Suryakencana in Mt. Gede Pangrango National Park, West Java. A good campsite requires a plan. Planning is done zoning area that can be used as a camping area without disturbing the existing ecosystem and equipped facilities so that users can feel comfortable while in the area of the campground. Alun-alun Suryakencana at an altitude of 2750 m asl is part of the Mount Gede Pangrango National Park of West Java. This research was conducted in October 2016-August 2017, this research method refers to Rachman's (1984) complete thinking process in Norma (2013) which applies secondary data analysis at field study stage which consists of inventory, analysis, synthesis, concept, and planning. The final result of this planning is a Campsite Plan that is implemented in Alun-alun Suryakencana.


2014 ◽  
Vol 35 (3) ◽  
pp. 035018 ◽  
Author(s):  
Martin Erdmann ◽  
Robert Fischer ◽  
Christian Glaser ◽  
Dennis Klingebiel ◽  
Raphael Krause ◽  
...  

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