scholarly journals Stock Assessment of 19 Perciformes in the Beibu Gulf, China, Using a Length-Based Bayesian Biomass Method

2021 ◽  
Vol 8 ◽  
Author(s):  
Gang Hou ◽  
Hui Zhang ◽  
Jinrun Wang ◽  
Yanying Chen ◽  
Jianbin Lin
Keyword(s):  
Stock Assessment ◽  
Beibu Gulf ◽  
Limited Data ◽  
Length Frequency ◽  
Optimum Length ◽  
New Approach ◽  
Fish Stocks ◽  
Fish Resources ◽  
Fishery Resources ◽  
The Mean

The Beibu Gulf in China is rich in fish resources. However, only a small number of commercially developed fish stocks have been specifically assessed owing to limited data and expertise. In this study, 19 perciform fish populations in the Beibu Gulf were assessed using a length-based Bayesian biomass (LBB) estimator method, which is a new approach to evaluate a fishery’s status using length frequency (LF) data. The results showed that only 21% of the evaluated stocks were healthy and 79% were overfished. In particular, 26 and 21% of the assessed species had collapsed and were grossly overfished, respectively. Only 11 and 21% of the assessed species were slightly overfished and overfished, respectively. The ratios between the mean and optimum length (Lmean/Lopt) and between the mean length at first capture and the mean length, which maximizes catch and biomass (Lc/Lc_opt), were below one in 14 out of the 19 stocks, suggesting a truncated length structure and fishing of undersized individuals. The ratio of the 95th percentile length to asymptotic length L95th/Linf was close to one (>0.9) in 10 of 19 stocks, suggesting that at least some large fish were still present. Our research confirmed that the fishery resources in the Beibu Gulf were seriously overfished and provided evidence that LBB was an efficient method to evaluate the fishery resources. Fishery managers need to take specific measures to restore fishery resources.

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.

scholarly journals Growth, Mortality and Exploitation Levels of Sphyraena sphyraena (Pisces: Sphyraenidae) and Apsilus fuscus (Pisces: Lutjanidae) in Ghanaian Waters

2021 ◽  
Vol 2 (1) ◽  
pp. 16-23
Author(s):  
Joseph Aggrey-Fynn ◽  
Divine Worlanyo Hotor
Keyword(s):  
Growth Parameters ◽  
Total Mortality ◽  
Growth Function ◽  
Frequency Data ◽  
Length Frequency ◽  
Fish Stocks ◽  
Von Bertalanffy Growth Function ◽  
Inshore Waters ◽  
The Mean ◽  
Length Frequency Data

Sphyraena sphyraena (Linnaeus, 1758) and Apsilus fuscus (Valenciennes, 1830) are commercially important fish species in Ghana. The stocks are exploited mainly by the artisanal and semi-industrial fisheries. Growth and mortality rates, and exploitation levels of the two stocks in inshore waters of Ghana were assessed as a contribution to fill the knowledge gap on the species. Samples were obtained from three landing sites along the coast of Ghana from February to July, 2017. Length-frequency data were used to estimate growth, mortality and exploitation ratios. The modal class for S. sphyraena was 37.0–39.9 cm total length (TL) and 34.0–35.9 cm TL for A. fuscus. The length and weight relationships established that growth in S. sphyraena was negative allometric, whereas that of A. fuscus was isometric. The estimated growth parameters from the length frequency data fitted with the von Bertalanffy growth function were asymptotic length (L∞) of 69.9 cm TL for S. sphyraena and 53.5 cm TL for A. fuscus. The growth constant (K) was calculated as 1.64 yr-1 for S. sphyraena and 0.50 yr-1 for A. fuscus. The mean length-at-first capture (Lc) was found to be lower than the mean length at sexual maturity (Lm) for both species. The sex ratio showed a dominance of females over males in S. sphyraena, and 1:1 for A. fuscus. The total mortality rate (Z) for S. sphyraena was more than for A. fuscus. The estimated natural mortality (M) was 1.88 yr-1 for S. sphyraena and 0.74 yr-1 for A. fuscus whilst fishing mortality (F) rate was 3.04 yr-1 for S. sphyraena and 0.93 yr-1 for A. fuscus. The exploitation ratio showed that both fish stocks were exploited over the optimum levels. The estimated population parameters of the species obtained from the study, therefore, might be useful for the sustainable management of the stocks.

A New Approach to Length–Frequency Analysis: Growth Structure

1980 ◽  
Vol 37 (9) ◽  
pp. 1337-1351 ◽  
Author(s):  
Jon Schnute ◽  
David Fournier
Keyword(s):  
Frequency Analysis ◽  
Likelihood Estimation ◽  
Von Bertalanffy ◽  
Length Frequency ◽  
New Approach ◽  
New Methods ◽  
The Mean ◽  
Standard Deviations ◽  
Using Data ◽  
Length Frequency Analysis

This paper presents a new approach to length–frequency analysis which takes account of biological structure in the mean lengths and standard deviations in length for various age-classes of fish. The new methods help determine biologically meaningful solutions, even when earlier methods lead to an ambiguous set of competing solutions. The structure of the standard deviations turns out to be especially important. For describing the means, new parameters are defined for von Bertalanffy growth which prove to have greater biological meaning and numerical stability than L∞, K, and t0. These new parameters can often be estimated easily from the raw data in cases where the species experiences a slowing of growth with age. This paper also presents χ2 methods which can be used to rank competing solutions, although the results are not definitive. All methods are illustrated using data previously published for pike and abalone. An appendix describes in detail the computer programs required for the analysis.Key words: length–frequency analysis, aging of samples, von Bertalanffy growth, growth, maximum likelihood estimation, nonlinear estimation

scholarly journals DAMPAK SUBSIDI SOLAR TERHADAP KELESTARIAN SUMBER DAYA IKAN DI BITUNG, SULAWESI UTARA

2017 ◽  
Vol 7 (1) ◽  
pp. 1
Author(s):  
Yesi Dewita Sari ◽  
Estu Sri Luhur ◽  
Armen Zulham
Keyword(s):  
Systems Analysis ◽  
Fishing Effort ◽  
Operating Costs ◽  
Subsidy Policy ◽  
Fish Stocks ◽  
Fish Resources ◽  
Fishery Resources ◽  
Dynamical Systems Analysis ◽  
Operational Costs ◽  
The Impact

Penelitian bertujuan mengetahui dampak penetapan subsidi harga solar terhadap kelestarian sumber daya ikan telah dilakukan di Pelabuhan Perikanan Samudera Bitung Kota Bitung pada Bulan April, Agustus dan Oktober 2010. Analisis pendugaan parameter biologi dilakukan dengan menggunakan model surplus produksi berdasarkan metode Clark, Yoshimoto and Pooley (CYP). Adapun analisis dinamika dan hubungan sebab akibat antara eksploitasi sumber daya perikanan dengan usaha penangkapan ikan dilakukan dengan metode analisis sistem dinamik. Hasil penelitian menunjukkan bahwa pada kondisi baseline (harga solar Rp 4.500 per liter), rata-rata harga ikan Rp 6.200 per kg dan biaya operasional Rp 14.924.373 per trip maka jumlah effort yang diperbolehkan adalah sebanyak 1.601 trip per bulan dan jumlah produksi 982 ton per bulan serta ketersediaan stok ikan 1.306 ton. Tanpa subsidi solar (Rp 7.500 per liter) maka terjadi peningkatan biaya operasional per trip sebesar 36,76% (Rp 20.410.696 per trip), sedangkan jumlah effort yang diperbolehkan relatif tetap (1.600 trip per bulan). Hasil ini menunjukkan bahwa kebijakan subsidi solar tidak memberikan dampak signifikan terhadap kelestarian sumber daya ikan di Bitung. Oleh karena itu, subsidi solar harus tetap diberikan kepada nelayan di Bitung agar mereka dapat melakukan pemanfaatan sumber daya ikan secara berkelanjutan disamping mengurangi potensi pemanfaatannya oleh nelayan negara tetangga secara ilegal.Title: Impact of Fuel Subsidy on Sustainablity to Fishery Resources in Bitung, North SulawesiThe study aims to determine the impact of diesel price fixing subsidy to sustainability of fish resources has been carried out in the port of Ocean Fishery Bitung, Bitung City in April, August and October 2010. Analysis of biological parameter estimation is done using a production surplus model based on the method of Clark, Yoshimoto and Pooley (CYP). The analysis of the dynamics and the causal relationship between the exploitation of fishery resources to fishing effort carried out by the method of dynamical systems analysis. The results showed that in the baseline condition (diesel price of Rp 4,500 per liter), the average price of Rp 6,200 per kg of fish and operational costs Rp 14,924,373 per trip allowed the amount of effort that is as much a 1601 trips per month and the amount of production of 982 tons per month, and 1306 tons of fish stocks. Without the solar subsidy (Rp 7,500 per liter), then an increase in operating costs per trip by 36.76% (Rp 20,410,696 per trip), while the amount of effort that allowed relatively fixed (1,600 trips per month). These results indicate that the diesel subsidy policy does not provide a significant impact on the sustainability of fish resources in Bitung. Therefore, solar subsidies should be given to fishermen in Bitung so that they can perform the utilization of fish resources in a sustainable manner as well as reducing the potential for use by fishermen neighboring countries illegally.

scholarly journals Seasonal Variation and Assessment of Fish Resources in the Yangtze Estuary Based on Environmental DNA

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2874
Author(s):  
Hui Jia ◽  
Yibang Wang ◽  
Susumu Yoshizawa ◽  
Wataru Iwasaki ◽  
Yuquan Li ◽  
...  
Keyword(s):  
Environmental Dna ◽  
Yangtze Estuary ◽  
The Yangtze Estuary ◽  
Annual Fish ◽  
Fish Stocks ◽  
Marine Communities ◽  
Fish Resources ◽  
The Past ◽  
Fishery Resources ◽  
Four Seasons

In the past few years, environmental DNA (eDNA) techniques have been used to monitor marine communities. Research indicates that eDNA is an effective tool for monitoring fishery resources. This study analyzed the seasonal variations in fish resources in the Yangtze Estuary, China, using eDNA. A total of 103 water samples were collected from the Yangtze Estuary across the four seasons in 2019—20 samples in February, 28 in May, 28 in August and 27 in November. Our research successfully detected the fishery resources of the Yangtze Estuary. We found significant differences according to the season. The results showed that 59 species were identified in 2019 (20 in February, 16 in May, 5 in August and 45 in November) and fish species varied widely over the four seasons. Furthermore, our samples revealed significant differences in annual fish stocks in the Yangtze Estuary, compared with eDNA data from 2018 and with traditional surveys from past years. Overall, eDNA is a useful emerging tool to assist with monitoring and protecting fish resources for the Yangtze Estuary.

scholarly journals Population dynamics of Chrysichthys nigrodigitatus (Lacépède, 1803) in Ikere-gorge, Oyo State, Nigeria

2021 ◽  
Vol 56 (1) ◽  
pp. 79-86
Author(s):  
S.O. Ajagbe ◽  
D.O. Odulate ◽  
R.O. Ajagbe ◽  
O.S. Ariwoola ◽  
F.I. Abdulazeez ◽  
...  
Keyword(s):  
Assessment Tool ◽  
Growth Parameters ◽  
Stock Assessment ◽  
Total Mortality ◽  
Fishing Mortality ◽  
Length Frequency ◽  
Optimum Length ◽  
Growth Coefficient ◽  
Exploitation Rate ◽  
Length Frequency Data

The growth and mortality parameters of Chrysichthys nigrodigitatus were estimated to assess the sustainability of its exploitation in Ikere-gorge, Oyo State, Nigeria. A total of 1210 of Chrys­ichthys nigrodigitatus were sampled from fishermen catches between January, 2017 and Decem­ber, 2018. C. nigrodigitatus were exploited with gillnet, cast net and traps (Malian trap net and bamboo). Total lengths were measured with fish measuring board. The FAO-ICLARM Stock Assessment Tool (FiSAT II) software was used to analyze length-frequency data of the fish. The estimated growth parameters are: asymptotic length is 60.9 cm, growth coefficient is 0.96, optimum length is 38.51 cm; length at maturity is 33.44 cm while length-at-first-capture is 12.62 cm. The estimated mortality parameters are: total mortality is 3.29 per year, natural mortality is 1.43 per year and fishing mortality is 1.86. It was observed that C. nigrodigitatus of Ikere-gorge were more vulnerable to exploitation at sizes less than their length at maturity. Likewise, the ex­ploitation rate (E = 0.57 yr-1) is greater than sustainable exploitation rate (Emax = 0.46 yr-1). This shows that exploitation of C. nigrodigitatus in Ikere-gorge is not sustainable. Therefore, there is need to reduce fishing pressure on C. nigrodigitatus to ensure its sustainability in Ikere-gorge.

scholarly journals Stock Assessment of Exploited Sardine Populations from Northeastern Bay of Bengal Water, Bangladesh Using the Length-Based Bayesian Biomass (LBB) Method

2021 ◽  
Vol 9 (10) ◽  
pp. 1137
Author(s):  
Partho Protim Barman ◽  
Qun Liu ◽  
Md. Abdullah Al-Mamun ◽  
Petra Schneider ◽  
Mohammad Mojibul Hoque Mozumder
Keyword(s):  
Bay Of Bengal ◽  
Stock Assessment ◽  
Mesh Size ◽  
Length Frequency ◽  
Optimum Length ◽  
Stock Status ◽  
Fisheries Resources ◽  
Fishing Gears ◽  
The Status

Stock assessment is necessary to understand the status of fishery stocks. However, for the data-poor fishery, it is very challenging to assess the stock status. The length-based Bayesian biomass (LBB) technique is one of the most powerful methods to assess the data-poor fisheries resources that need simple length frequency (LF) data. Addressing the present gap, this study aimed to assess the stock status of three sardines (Sardinella fimbriata, Dussumieria acuta, and D. elopsoides) in the Bay of Bengal (BoB), Bangladesh using the LBB method. The estimated relative biomass for S. fimbriata was B/B0 < BMSY/B0, indicating the overfished biomass, while the assessed B/B0 > BMSY/B0 for D. acuta and D. elopsoides indicates healthy biomass. Additionally, for S. fimbriata, the length at first landing was smaller than the optimum length at first landing (Lc < Lc_opt), indicating an overfishing status, but a safe fishing status was assessed for D. acuta and D. elopsoides (Lc > Lc_opt). Therefore, increasing the mesh size of fishing gears may help to ensure the long-term viability of sardine populations in the BoB, Bangladesh.

Pescadores migrantes: análisis de su dinámica e integración Social

2019 ◽  
Vol 37 (3) ◽  
pp. 18
Author(s):  
Fernando González Laxe
Keyword(s):  
Renewable Resources ◽  
Sustainable Management ◽  
Social Groups ◽  
Technological Innovations ◽  
Social Competition ◽  
Factors Affecting ◽  
Fish Stocks ◽  
Fishery Resources ◽  
Migration Dynamics ◽  
The Many

The globalization of the economy encourages massive population displacements and inevitably generates a cosmopolitization of societies. This leads to concern, misunderstanding and rejection. The most vulnerable social groups in society can perceive the population as intruders and enemies in social competition. Undoubtedly, the extreme spatial instability of fishery resources is among the many factors affecting migration dynamics. Various reasons for the mobility of fishermen are relevant around this concept. These include aspect related to traditions, to the capitalisation of activity, to technological innovations, and to innovation exchanges concerning the location of fish stocks. This article reflects on spatial increase of fishermen’s. The analyse are part of the paradigm of the sustainable management of common renewable resources, in particular fishery resources. It presents three lines of analysis: the reason for mobility; the choice of destination; and are the integration into host units.

A new simpler approach to measure the strength of toe plantar flexion requiring no mechanical restraint with a light-weight device

2021 ◽  
pp. 095441192110029
Author(s):  
Yuko Komuro ◽  
Yuji Ohta
Keyword(s):  
Plantar Flexion ◽  
Mean Value ◽  
Simple Approach ◽  
Light Weight ◽  
New Approach ◽  
Mean Values ◽  
Mechanical Restraint ◽  
Significant Difference ◽  
Ankle Joints ◽  
The Mean

Conventionally, the strength of toe plantar flexion (STPF) is measured in a seated position, in which not only the target toe joints but also the knee and particularly ankle joints, are usually restrained. We have developed an approach for the measurement of STPF which does not involve restraint and considers the interactions of adjacent joints of the lower extremities. This study aimed to evaluate this new approach and comparing with the seated approach. A thin, light-weight, rigid plate was attached to the sole of the foot in order to immobilize the toe area. Participants were 13 healthy young women (mean age: 24 ± 4 years). For measurement of STPF with the new approach, participants were instructed to stand, raise the device-wearing leg slightly, plantar flex the ankle, and push the sensor sheet with the toes to exert STPF. The sensor sheet of the F-scan II system was inserted between the foot sole and the plate. For measurement with the seated approach, participants were instructed to sit and push the sensor with the toes. They were required to maintain the hip, knee, and ankle joints at 90°. The mean values of maximum STPF of the 13 participants obtained with each approach were compared. There was no significant difference in mean value of maximum STPF when the two approaches were compared (new: 59 ± 23 N, seated: 47 ± 33 N). The coefficient of variation of maximum STPF was smaller for data obtained with the new approach (new: 39%, seated: 70%). Our simple approach enables measurement of STPF without the need for the restraints that are required for the conventional seated approach. These results suggest that the new approach is a valid method for measurement of STPF.

Size Distributions and Growth of the Fan-shell Pinna bicolor Gmelin (Mollusca : Eulamellibranchia) in South Australia

1979 ◽  
Vol 30 (1) ◽  
pp. 25 ◽  
Author(s):  
AJ Butler ◽  
FJ Brewster
Keyword(s):  
South Australia ◽  
Adductor Muscle ◽  
Size Distributions ◽  
Limited Data ◽  
Length Frequency ◽  
Age Classes ◽  
Frequency Distributions ◽  
Growth And Survival ◽  
Random Samples ◽  
Variable Success

Fourteen random samples of Pinna bicolor were collected over a period of 31 months from 6 m depth in Gulf St Vincent off Edithburgh, South Australia. The length-frequency distributions suggest that: P. bicolor larvae settle in spring but with variable success; growth of newly settled young is rapid over summer; by age 1 year their modal shell length is about 20 cm; by age 2 it is about 26 cm; they may survive substantially longer than 3 years so that a length-class of mode c. 35 cm is always present and is composed of several age-classes not necessarily equally represented. These suggestions are corroborated by limited data on adductor muscle scars, the development of epibiota on the shells, and the growth and survival of tagged animals over 9 months.

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