scholarly journals Spatially explicit estimation of fish length histograms, with application to anchovy habitats in the Bay of Biscay

2011 ◽  
Vol 68 (10) ◽  
pp. 2086-2095 ◽  
Author(s):  
Pierre Petitgas ◽  
Mathieu Doray ◽  
Jacques Massé ◽  
Patrick Grellier
Keyword(s):  
Stock Assessment ◽  
Spatially Explicit ◽  
Fish Length ◽  
Bay Of Biscay ◽  
Length Frequency ◽  
Polynomial Coefficients ◽  
Complex Information ◽  
Novel Approach ◽  
Frequency Map ◽  
Spatially Varying

Abstract Petitgas, P., Doray, M., Massé, J., and Grellier, P. 2011. Spatially explicit estimation of fish length histograms, with application to anchovy habitats in the Bay of Biscay. – ICES Journal of Marine Science, 68: 2086–2095. Fish length frequency histograms from research surveys are of prime importance for identifying habitats of different life stages, as well as for stock assessment. However, no method has thus far been available for mapping these histograms as spatially varying curves. Here, a procedure is applied to map spatially connected curves, and detail is given on how it can be applied to map the length frequency histograms. At each sample location, a fish length frequency histogram is given as a vector of non-independent values. The histogram is first modelled as a polynomial expansion on the basis of orthogonal polynomials. Then, the polynomial coefficients are mapped by co-kriging, after fitting a model of co-regionalization. The length frequency map is finally derived by linearly combining maps of polynomial coefficients. An estimation variance associated with the map is also derived. Maps of anchovy length distributions are produced by applying the method to midwater trawl length data from the PELGAS acoustic surveys in the Bay of Biscay. This novel approach extends the application of kriging techniques to curves or functions, opening new perspectives for mapping more complex information than just the values of fish density.

scholarly journals Stock Estimates of White Pomfret (Pampus argenteus) Based on Length and Weight Data in Pangandaran Waters

2019 ◽  
pp. 1-13
Author(s):  
Yaris Hikmawansyah ◽  
Yuli Andriani ◽  
Alexander Muhammad Akbar Khan ◽  
Lantun Paradhita Dewanti
Keyword(s):  
Stock Assessment ◽  
Total Mortality ◽  
Fish Population ◽  
Assessment Tools ◽  
Fish Length ◽  
Growth Equation ◽  
Length Frequency ◽  
Pampus Argenteus ◽  
Exploitation Rate ◽  
Weight Data

White pomfret (Pampus argenteus) is one of the economically important fish and includes the leading commodity in Pangandaran Waters. Information on fishing biology of those species were still limited. The purpose of this study is to determine stock estimates including length-weight relationship, age group, growth, mortality and exploitation rate of white pomfret. Monthly length-frequency data have been collected from November 2018 to August 2019 at Cikidang fish auction. Fish length-frequency distribution was separated into a normal distribution using the Bhattacharya method with software of FiSAT (FAO-ICLARM Stock Assessment Tools). Estimation of population parameters used analytical model application with ELEFAN-1 (Electronic Length Frequency Analysis) program. The results showed that lengths distribution of white pomfret ranged between 19.3 cm - 36.8 cmTL. Length-weight relations was negatively allometric (W = 0,1184L2,3719). Growth equation of white pomfret is Lt = 53.04 (1-e-0.26(t)). Natural mortality (M) was 0.60/year, fishing mortality (F) was 3.04/year and total mortality (Z) was 3.64/ year. The exploitation rate (E) was 0.84. It is mean that higher than optimal exploitation so that the white pomfret fish population in a state of overfished. It is necessary to better policy in the management of white pomfret through precaution approach and describing of biological and fishing aspect in Pangandaran Waters.

Reference points for the length-based indicator Lmax5% for use in the assessment of data-limited stocks

2019 ◽  
Vol 76 (7) ◽  
pp. 2125-2139 ◽  
Author(s):  
Tanja Miethe ◽  
Yves Reecht ◽  
Helen Dobby
Keyword(s):  
Life Histories ◽  
Stock Assessment ◽  
Reference Points ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Simulation Tools ◽  
Spawning Potential Ratio ◽  
The Mean ◽  
Commercial Sources ◽  
Length Frequency Data

Abstract In the absence of abundance indices from scientific surveys or commercial sources, reliable length frequency data from sampled commercial catches can be used to provide an indirect assessment of fishing mortality. Length-based indicators are simple metrics which describe length frequency distributions. The length-based indicator Lmax5%, the mean length of the largest 5% of individuals in the catch, combined with appropriately selected reference points, can be used to evaluate the presence of very large individuals in the catch and hence determine exploitation level. Using analytical per-recruit models, we derive reference points consistent with a spawning potential ratio of 40%. The reference points depend on the life history parameters for natural mortality, maturity, and growth (M, Lmat, L∞, k, CVL∞). Using available simulation tools, we investigate the sensitivity of the reference points to errors in these parameters and explore the usefulness of particular reference points for management purposes for stocks with different life histories. The proposed reference points are robust to uncertainty in length at first capture, Lc, and take into account the maturation schedule of a species. For those stocks with high M/k ratios (>1), Lmax5%, combined with the appropriate reference point, can be used to provide a data-limited stock assessment.

Application of the otolith weight – age relationship for the pilchard, Sardinops sagax neopilchardus

1995 ◽  
Vol 52 (4) ◽  
pp. 657-664 ◽  
Author(s):  
W. J. Fletcher
Keyword(s):  
Maximum Size ◽  
Steady Increase ◽  
Average Weight ◽  
Fish Length ◽  
Natural Mortality ◽  
Length Frequency ◽  
Age Classes ◽  
Frequency Distributions ◽  
Southwestern Australia ◽  
Sardinops Sagax

Adult pilchard (Sardinops sagax neopilchardus) from southwestern Australia held in fish cages for 1 year showed minimal increase in mean length but a steady increase in mean otolith weight (1.61–1.83 mg); this increase (0.22 mg) closely parallels the previously calculated mean difference between adjacent age classes (0.24 mg). Modes in otolith weight frequency distributions of fishery-caught pilchards, previously suggested as corresponding with separate year classes, generally persisted and progressed through subsequent samples. By contrast, fish length frequency distributions of these samples showed no consistent modal progression. The average weight of otoliths for year classes 2–8 were used to calculate growth rates: following sexual maturity, at age 2, males grew to a significantly smaller maximum size than females (L∞ = 162 and 172 mm respectively). The otolith weight – age relationship, validated by following a cohort of unusually low abundance as it moved through the fishery, indicated that recruitment to the fishery generally began at age 2 but was not complete until age 4. These data have been successfully used in forecasting the catch rate of the fishery up to 2 years in advance and providing an estimate of the rate for natural mortality of 0.43.

scholarly journals Incoherent dimensionality in fisheries management: consequences of misaligned stock assessment and population boundaries

2020 ◽  
Author(s):  
Aaron M Berger ◽  
Jonathan J Deroba ◽  
Katelyn M Bosley ◽  
Daniel R Goethel ◽  
Brian J Langseth ◽  
...  
Keyword(s):  
Population Structure ◽  
Stock Assessment ◽  
Spatially Explicit ◽  
Spatial Simulation ◽  
Management Options ◽  
Spatially Explicit Models ◽  
Fisheries Policy ◽  
Simulation Estimation ◽  
Definition Of ◽  
Dynamic Population

Abstract Fisheries policy inherently relies on an explicit definition of management boundaries that delineate the spatial extent over which stocks are assessed and regulations are implemented. However, management boundaries tend to be static and determined by politically negotiated or historically identified population (or multi-species) units, which create a potential disconnect with underlying, dynamic population structure. The consequences of incoherent management and population or stock boundaries were explored through the application of a two-area spatial simulation–estimation framework. Results highlight the importance of aligning management assessment areas with underlying population structure and processes, especially when fishing mortality is disproportionate to vulnerable biomass among management areas, demographic parameters (growth and maturity) are not homogenous within management areas, and connectivity (via recruitment or movement) unknowingly exists among management areas. Bias and risk were greater for assessments that incorrectly span multiple population segments (PSs) compared to assessments that cover a subset of a PS, and these results were exacerbated when there was connectivity between PSs. Directed studies and due consideration of critical PSs, spatially explicit models, and dynamic management options that help align management and population boundaries would likely reduce estimation biases and management risk, as would closely coordinated management that functions across population boundaries.

scholarly journals Age, Growth and Ovarian Histology of Sardinella aurita (Valenciennes, 1847) in the South of Atlantic Moroccan Coast

2021 ◽  
Vol 21 (04) ◽  
pp. 191-204
Author(s):  
Ayoub Baali ◽  
Oum Keltoum Belhsen ◽  
Khalil Chahdi Ouazzani ◽  
Khadija Amenzoui ◽  
Ahmed Yahyaoui
Keyword(s):  
Frequency Distribution ◽  
Stock Assessment ◽  
Atlantic Coast ◽  
Age Groups ◽  
Age Determination ◽  
Length Frequency Distribution ◽  
Length Frequency ◽  
The South ◽  
Moroccan Coast ◽  
Sardinella Aurita

Otoliths reading and length frequency distribution were used for age determination and growth estimation of Sardinella aurita (round sardinella) stock of Southern Atlantic coast of Morocco. Both otoliths' method for age determination and Bhattacharya’s method for length frequency analysis showed five age groups. The growth performance index revealed that there is significant accordance among method of length frequency distribution and otoliths reading for stock assessment studies of Sardinella aurita stock in the south of Morocco. The microscopic observation of female gonads using histology method was investigated for the first time in our study area and confirms the presence of five principal stages of ovary of sardinella aurita: immature, maturing virgin and recovering spent, mature (or pre-spawning phase), spawning, post-spawning or spent. In addition, our results of the fecundity showed that the mean relative fecundity obtained is estimated at 193 ± 98 oocytes/g which is lower compared to those obtained in other areas in the Atlantic coast.

scholarly journals Neuron Interaction Based Representation Composition for Neural Machine Translation

2020 ◽  
Vol 34 (05) ◽  
pp. 8204-8211
Author(s):  
Jian Li ◽  
Xing Wang ◽  
Baosong Yang ◽  
Shuming Shi ◽  
Michael R. Lyu ◽  
...  
Keyword(s):  
Machine Translation ◽  
Semantic Information ◽  
Low Rank ◽  
Strong Interactions ◽  
Low Rank Approximation ◽  
Neural Machine Translation ◽  
First Order ◽  
Complex Information ◽  
Novel Approach ◽  
Rank Approximation

Recent NLP studies reveal that substantial linguistic information can be attributed to single neurons, i.e., individual dimensions of the representation vectors. We hypothesize that modeling strong interactions among neurons helps to better capture complex information by composing the linguistic properties embedded in individual neurons. Starting from this intuition, we propose a novel approach to compose representations learned by different components in neural machine translation (e.g., multi-layer networks or multi-head attention), based on modeling strong interactions among neurons in the representation vectors. Specifically, we leverage bilinear pooling to model pairwise multiplicative interactions among individual neurons, and a low-rank approximation to make the model computationally feasible. We further propose extended bilinear pooling to incorporate first-order representations. Experiments on WMT14 English⇒German and English⇒French translation tasks show that our model consistently improves performances over the SOTA Transformer baseline. Further analyses demonstrate that our approach indeed captures more syntactic and semantic information as expected.

scholarly journals A Territory-Oriented Approach to Operationilize Sustainable Management

2019 ◽  
pp. 1-15
Author(s):  
Ana L. Burgos ◽  
Alejandro Velázquez
Keyword(s):  
Sustainable Management ◽  
Negative Impact ◽  
Land Use Policy ◽  
Spatially Explicit ◽  
Decision Making Process ◽  
Clear Understanding ◽  
Novel Approach ◽  
Economic Forces ◽  
The Subject ◽  
Oriented Approach

Sustainable science ultimately seeks to minimize the negative impact of human activities on nature, however its role is regarded as limited, chiefly because it lacks a robust spatial framework to join ecological and social processes. Space, from a territorial perspective, is the result of historical interactions between socio-economic forces governing access to natural resources. This paper provides a territorial-oriented approach to improve land use policy from a spatially explicit perspective. We develop a novel approach, namely ‘Territorial Configuration’ implying the dissection of the geographic continuum into territorial conglomerates. These are delimited by a range of meaningfully socio-histori calliaisonen compassing a clear understanding of how space is controlled by space holders trigging proximal and underlying governing processes. We discuss how the territorial configuration facilitates overcoming pending issues inland use policy, such as, ecological and geographical articulation, legitimate decision-making process, and increase of certainty on the subject of management among others.

scholarly journals Modular and spatially explicit: A novel approach to system dynamics

2017 ◽  
Vol 94 ◽  
pp. 48-62 ◽  
Author(s):  
Patrick Wingo ◽  
Allen Brookes ◽  
John Bolte
Keyword(s):  
System Dynamics ◽  
Spatially Explicit ◽  
Novel Approach

scholarly journals Target Strength and swimbladder morphology of Mueller’s pearlside (Maurolicus muelleri)

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
B. Sobradillo ◽  
G. Boyra ◽  
U. Martinez ◽  
P. Carrera ◽  
M. Peña ◽  
...  
Keyword(s):  
Relevant Information ◽  
Target Strength ◽  
Fish Length ◽  
Mesopelagic Fish ◽  
Bay Of Biscay ◽  
Numerical Abundance ◽  
Density Filter ◽  
Pressure Changes ◽  
First Time ◽  
Best Fit

AbstractIn the last few years, there has been increasing interest in the commercial exploitation of mesopelagic fish and a trawl-acoustic methodology has been recommended to make estimates of abundance of these resources. This study provides relevant information on the scattering properties of a key mesopelagic fish species in the Bay of Biscay, Mueller’s pearlside (Maurolicus muelleri), necessary to convert the acoustic density into numerical abundance. The target strength (TS) of pearlside was estimated for the first time at five frequencies commonly used in acoustic surveys. A high-density filter was applied to reduce the bias derived from overlapping echoes erroneously assigned to single targets. Its relationship with fish length (b20) was also determined (−65.9 ± 2, −69.2 ± 3, −69.2 ± 2, −69.5 ± 2.5 and −71.5 ± 2.5 dB at 18, 38, 70, 120 and 200 kHz, respectively). Biomass estimates of pearlside in the Bay of Biscay during the four years of study (2014–2017) are given using the 38 kHz frequency. Morphological measurements of the swimbladder were obtained from soft X-ray images and used in the backscattering simulation of a gas-filled ellipsoid. Pearlside is a physoclist species, which means that they can compensate the swimbadder volume against pressure changes. However, the best fit between the model and the experimental data showed that they lose that capacity during the trawling process, when the swimbladder volume is affected by Boyle’s law.

scholarly journals Demonstration of a spatially explicit, tag-integrated stock assessment model with application to three interconnected stocks of yellowtail flounder off of New England

2014 ◽  
Vol 72 (1) ◽  
pp. 164-177 ◽  
Author(s):  
Daniel R. Goethel ◽  
Christopher M. Legault ◽  
Steven X. Cadrin
Keyword(s):  
New England ◽  
Integrated Assessment ◽  
Stock Assessment ◽  
Assessment Model ◽  
Spatially Explicit ◽  
Closed Population ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea ◽  
Stock Assessments ◽  
Source Sink

Abstract Ignoring population structure and connectivity in stock assessment models can introduce bias into important management metrics. Tag-integrated assessment models can account for spatially explicit population dynamics by modelling multiple population components, each with unique demographics, and estimating movement among them. A tagging submodel is included to calculate predicted tag recaptures, and observed tagging data are incorporated in the objective function to inform estimates of movement and mortality. We describe the tag-integrated assessment framework and demonstrate its use through an application to three stocks of yellowtail flounder (Limanda ferruginea) off New England. Movement among the three yellowtail flounder stocks has been proposed as a potential source of uncertainty in the closed population assessments of each. A tagging study was conducted during 2003–2006 with over 45 000 tagged fish released in the region, and the tagging data were included in the tag-integrated model. Results indicated that movement among stocks was low, estimates of stock size and fishing mortality were similar to those from conventional stock assessments, and incorporating stock connectivity did not resolve residual patterns. Despite low movement estimates, new interpretations of regional stock dynamics may have important implications for regional fisheries management given the source-sink nature of movement estimates.

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