Comment on “Differences in predicted catch composition between two widely used catch equation formulations”Appears in Can. J. Fish. Aquat. Sci. 66: 126–132.

2010 ◽  
Vol 67 (4) ◽  
pp. 763-765 ◽  
Author(s):  
R. I.C. Chris Francis
Keyword(s):  
Stock Assessment ◽  
Fishing Gear ◽  
Fishing Mortality ◽  
Instantaneous Rate ◽  
Exploitation Rate ◽  
Catch Composition ◽  
Continuous Formulation

Branch (2009. Can. J. Fish. Aquat. Sci. 66: 126–132) described the two most common catch equation formulations in stock assessment models: the continuous (Baranov) one, which represents fishing mortality as an instantaneous rate, F, and the discrete one, in which it is represented as an exploitation rate, u. He claimed that the continuous formulation is preferable at high fishing mortality where a fish could encounter multiple sets of gear within a year. This claim is wrong for two reasons. First, it is based on the false supposition that the discrete catch equations require the assumption that fish encounter at most only one set of fishing gear in a year. Second, it is not possible to determine, for a specific stock assessment, whether one formulation is preferable to another solely on the basis of information about the fishery. The appropriate way to make this decision is to see which fits the data better.

Differences in predicted catch composition between two widely used catch equation formulations

2009 ◽  
Vol 66 (1) ◽  
pp. 126-132 ◽  
Author(s):  
Trevor A. Branch
Keyword(s):  
Age Groups ◽  
Correct Choice ◽  
Fishing Gear ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Gear Selectivity ◽  
Different Types ◽  
Catch Composition ◽  
Continuous Formulation ◽  
Discrete Formulation

Fishing gear selectivity varies among different types of fish (e.g., species, age, sex, or length groups), but their relative catch composition also depends on the fishing process. The continuous (Baranov) formulation assumes that fishing mortality and natural mortality occur together during the fishing season and that there are multiple encounters between fish and fishing gear. For this formulation, predicted catch composition depends on fishing mortality, and at high fishing mortality levels the entire population can be caught provided the selectivity is nonzero for all age groups. In contrast, the discrete formulation assumes that fishing mortality occurs separately from natural mortality and that fish encounter at most only one set of fishing gear. The discrete formulation is easier to compute, but the predicted catch composition is independent of fishing mortality, and some of the population remains unexploitable. The correct choice of equations depends on the particular fishery and fishing mortality levels; at low fishing mortality levels the predictions differ little, but at high fishing mortality levels where multiple gear encounters could occur, the continuous formulation is preferable.

Reply to the comment by Francis on “Differences in predicted catch composition between two widely used catch equation formulations”Appears in Can. J. Fish. Aquat. Sci. 66: 126–132.

2010 ◽  
Vol 67 (4) ◽  
pp. 766-768
Author(s):  
Trevor A. Branch
Keyword(s):  
Entire Population ◽  
Fishing Gear ◽  
Fishing Mortality ◽  
Gear Selectivity ◽  
Catch Composition ◽  
Continuous Formulation ◽  
Discrete Formulation ◽  
Model Fits

Francis (2010. Can. J. Fish. Aquat. Sci. 67: 763–765) writes a thoughtful response detailing concerns with my suggestion that the continuous (Baranov) catch formulation is preferable to the discrete catch formulation when fishing mortality is high (T.A. Branch. 2009. Can. J. Fish. Aquat. Sci. 66: 126–132). He suggests the discrete formulation allows for multiple gear encounters and that formulation choice should depend on which formulation better fits the data. Here I first distinguish between gear selectivity and availability and then show that our two views are complementary: the original assumes fish groups with differing gear selectivity but full availability, whereas Francis assumes fish groups fully selected by fishing gear but with differing availability. I maintain that the discrete formulation only models a single instantaneous interaction between fish and fishing gear and therefore only part of the population can be caught if fish groups have equal gear selectivity that is less than 100%, whereas under the same assumptions, the continuous formulation would allow the entire population to be caught. Finally, when the balance between gear selectivity and availability is unknown, I agree that formulation choice could be driven by model fits to the data, although formulation choice could also be based on how the fishery operates.

scholarly journals Stock Assessment of Arius maculatus (Thurnberg, 1792) (Ariidae, Siluriformes) in Panguil Bay, Northwestern Mindanao

2020 ◽  
Vol 27 (1) ◽  
pp. 40-53
Author(s):  
Celestina Jumawan ◽  
Ephrime Metillo ◽  
Maria Theresa Mutia
Keyword(s):  
Stock Assessment ◽  
Total Suspended Solid ◽  
Suspended Solid ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Limited Information ◽  
K Value ◽  
Fishing Boat ◽  
Exploitation Rate ◽  
Ph Range

Arius maculatus, commonly known as spotted catfish and locally known as Tambangongo, has a great potential as an aquaculture species, but there is very limited information known for the stocks in Panguil Bay. This study aimed to assess the wild stocks of A.maculatus, and make an inventory of the fishing boat and gears in two stations in Panguil Bay, namely: Tangub, Misamis Occidental and Baroy, Lanao del Norte. Length frequencies were analyzed to provide estimates of growth, mortality, exploitation ratio, and recruitment pulse of A. maculatus in the bay. A total of 589 boats (324 motorized boats and 265 non-motorized boats) were recorded from the sites. There were 473 units of 15 types of fishing gear used in the sites and 6 types of these were only used in catching A. maculatus. A total of 3,259 specimens were collected for 12 months from the sites. The aquatic habitat of A. maculatus from the two sites was characterized by a pH range of 7.9-8.1, temperature of 28.5-29.1°C, salinity of 13.31-15.9 ppt, dissolved oxygen levels of 4.0-5.41 ppm, and total suspended solid values of 0.1-0.6 g/L. Reproductive biology analysis indicates that eggs start to mature from October to December, then spawning starts from January to March, and the fish fry recruitment starts in April and May. A. maculatus can grow up to 98.95 cm with an asymptotic length of 98.86 cm (K value = 0.35) equivalent to asymptotic weigth of 8,750 g. Mortality Z = 0.99, with natural mortality M = 0.67 and fishing mortality F = 0.33. This study revealed that A. maculatus in Panguil Bay is not over-exploited since the exploitation rate (E = 0.33) is minimal and large individuals can still be collected from the field.

scholarly journals DAERAHPENANGKAPAN, LAJUPANCINGDANPARAMETERPOPULASI IKAN GINDARA (Lepidocybium flavobrunneum) DI SAMUDERA HINDIA

2016 ◽  
Vol 8 (1) ◽  
pp. 49 ◽  
Author(s):  
Andi Bahtiar ◽  
Abram Barata ◽  
Dian Novianto
Keyword(s):  
Indian Ocean ◽  
Total Mortality ◽  
Growth Parameter ◽  
Fishing Ground ◽  
Fishing Mortality ◽  
Length Frequency ◽  
Instantaneous Rate ◽  
Exploitation Rate ◽  
The Indian Ocean ◽  
Longline Fisheries

<p><strong> </strong></p><p>Ikan gindara atau escolar <em>(Lepidocybium flavobrunneum</em><em>)</em>, umumnya tertangkap sebagai hasil tangkapan sampingan <em>(bycatch)</em> pada perikanan rawai tuna Indonesia.  Penelitian dilakukan dengan metode observasi onboard pada armada rawai tuna yang berbasis di Pelabuhan Benoa mulai bulan Agustus 2005 - Desember 2009 yang beroperasi di Samudera Hindia. Tujuan penelitian ini adalah memberikan informasi daerah penangkapan, menganalisis parameter populasi (umur, pertumbuhan, mortalitas) dan laju eksploitasi ikan gindara hasil tangkapan kapal rawai tuna di Samudera Hindia. Hasil penelitian menunjukan  ikan gindara yang tertangkap oleh kapal rawai tuna menyebar pada posisi geografis antara  9<sup>0</sup>-33<sup>0</sup> LS dan 76<sup>0</sup>-127<sup>0</sup> BT dengan nilai laju pancing (HR) ikan gindara tertinggi  pada tahun 2007 sebesar 0,15 dan terendah tahun 2005 yaitu 0,04, atau  rata-rata HR sebesar 0,10.  Ikan  yang tertangkap memiliki ukuran panjang cagak antara 35-193 cm dengan rata-rata 87,4 cm. Parameter populasi yang dianalisa dengan program FiSAT II diperoleh panjang asimtotik (L∞) = 201,60 cmFL, koefisien laju pertumbuhan (K) = 0,21 per tahun dan t<sub>0</sub> = -0,4755 tahun. Nilai dugaan mortalitas total (Z) sebesar 0,85 per tahun, nilai dugaan mortalitas alami (M) = 0,37 per tahun dan laju mortalitas penangkapan (F) = 0,48 per tahun. Laju eksploitasi (E = 0,56) menunjukkan bahwa pemanfaatan gindara di Samudera Hindia diatas nilai optimum yang disarankan yaitu E = 0,50.</p><p><em>Escolar (Lepidocybium flavobrunneum) commonly caught as bycatch in Indonesia tuna longline fisheries. The study was conducted on August 2005 - December 2009 with onboard observation of tuna longliner  based in Benoa fishing  port. The objectives of this study are provide information about fishing ground, analyzing parameters of population (age, growth, mortality) and exploitation rate of escolar caught by Indonesia tuna longliner in the Indian Ocean. The results showed that escolar caught by tuna fleets longliner spread on latitude and longitude 90<sup>0</sup>-33<sup>0</sup> S and 76<sup>0</sup>-127<sup>0</sup> E with highest hook rate in 2007 at 0.15 and lowest hook rate occurred in 2005 at 0.04, with average HR at 0.10. Length frequency distribution of escolar were 35-193 cmFL with length average of 87.4 cm. The Von Bertalanffy growth parameter for escolar in Indian Ocean were L∞ = 201.60 cm, K = 0.21 year<sup>-1</sup> and t<sub>0</sub> = -0,4755 years. The annual instantaneous rate of total mortality (Z) was 0.85 year<sup>-1</sup>. T</em><em>he natural mortality (M) was</em><em> 0.37 year<sup>-1</sup> and the fishing mortality (F) was 0.48 year<sup>-1</sup>. </em><em>The exploitation rate (E = 0.56)</em><em> </em><em>indicating that escolar</em><em> in the Indian Ocean has reached the optimum limit.</em></p>

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 Growth, Mortality and Yield-per-recruit of Nile Tilapia (Oreochromis niloticusM/em>) in Garmat Ali River, Iraq

2020 ◽  
Vol 8 (6) ◽  
Author(s):  
Ayat N. Salman ◽  
Abdul-Razak M Mohamed
Keyword(s):  
Assessment Tool ◽  
Growth Parameters ◽  
Stock Assessment ◽  
Total Mortality ◽  
Reference Points ◽  
Fishing Mortality ◽  
Exploitation Rate ◽  
Biological Target ◽  
Mean Size ◽  
Yield Per Recruit

The study was conducted to estimate the growth, mortality, recruitment and yield-per-recruit of Oreochromis niloticus from Garmat Ali River, Basrah, Iraq from October 2019 to September 2020. The population parameters were analyzed using the FAO-ICLARM stock assessment tool (FiSAT). A total of 2696 O. niloticus ranged from 7.0 to 25.0 cm and the sizes 13.0-18.0 cm constituted 64.2% of the total catch. The length-weight relationship was W= 0.012L3.109 suggesting that the species shows positive allometric growth. The growth parameters for the species were estimated as L∞= 30.45 cm, K= 0.45, to= -0.313 and Ǿ= 2.622. The coefficients of total mortality (Z), natural mortality (M) and fishing mortality (F) were 3.26, 1.03 and 2.24, respectively. The exploitation rate for the species computed to be 0.69. Fish were recruited to the fishery at a mean size of L50= 14.92 cm. The peak of recruitment was 23.51% in June. The analysis of yield-per-recruit (Y/R’) indicates that stock is not being overfished since the present exploitation rate was below the biological target reference points (E0.1 and Emax). So, more yields could be achieved by reducing the mesh sizes of the nets for fishing the species

scholarly journals Growth, mortality and stock assessment of greenback mullet, Planiliza subviridis from northwest Arabian Gulf, Iraq

2021 ◽  
Vol 6 (2) ◽  
pp. 142-148
Author(s):  
Abdul-Razak M. Mohamed ◽  
Ali H. Al-Hassani
Keyword(s):  
Mortality Rate ◽  
Stock Assessment ◽  
Population Analysis ◽  
Arabian Gulf ◽  
Total Mortality ◽  
Reference Points ◽  
Fishing Mortality ◽  
Fish Samples ◽  
Exploitation Rate ◽  
First Maturity

The growth, mortality and stock parameters of greenback mullet, Planiliza subviridis from Iraqi marine waters, northwest Arabian Gulf was assessed using FiSAT II software for length-frequency data collected from February 2020 to January 2021. P. subviridis is one of the species caught in large quantities as commercial by artisanal fishers. Fish samples were collected by the Shaheen steel-hulled dhow and from the artisanal fishermen. The total length and body weight relationship of fish was estimated as W= 0.034L2.670, indicating negative allometric growth. Of 3350 specimens, growth and mortality parameters were evaluated. The asymptotic length (L∞), growth rate (K) and growth performance index (Ø') were 33.8 cm, 0.30 and 2.535, respectively. The total mortality rate (Z), natural mortality rate (M), and fishing mortality rate (F) were 1.11, 0.74 and 0.38, respectively. The present exploitation rate (Epresent) of P. subviridis computed as 0.34. Length at first capture (L50) was 17.47 cm. Recruitment of P. subviridis was observed throughout the year, with a peak during July. The yield per recruit analysis indicates that the current exploitation rate was below the biological target reference points (E0.1 and Emax), which refers to the stock of P. subviridis is underexploited. Virtual population analysis results showed that mid-lengths (16-22 cm) experienced the highest fishing mortality. The length at first capture (L50) was higher than the length at first maturity (Lm) of the species. So, for management purposes, more yields could be obtained by increasing the fishing activities on this species for a substantial harvest.

scholarly journals LAJU PERTUMBUHAN, LAJU KEMATIAN DAN EKSPLOITASI IKAN TONGKOL KOMO, Euthynnus affinis (Cantor 1849), DI PERAIRAN SAMUDERA HINDIA BARAT SUMATERA

2015 ◽  
Vol 6 (2) ◽  
pp. 69
Author(s):  
Irwan Jatmiko ◽  
Ririk Kartika Sulistyaningsih ◽  
Duto Nugroho
Keyword(s):  
Stock Assessment ◽  
Total Mortality ◽  
Assessment Tools ◽  
Instantaneous Rate ◽  
Exploitation Rate ◽  
The Indian Ocean ◽  
Euthynnus Affinis ◽  
The One ◽  
Base Data ◽  
Length Frequency Data

Tongkol komo (Euthynnus affinis Cantor, 1849)merupakan hasil tangkapan utama bagi nelayan pukat cincin di Samudera Hindia sebelah barat Sumatera. Penelitian ditujukan untukmemperoleh data dan informasi tentang estimasi laju pertumbuhan, laju kematian dan laju eksploitasi ikan tongkol komo. Analisis dilakukan berdasarkan himpunan data frekuensi panjang cagak sebanyak 1.325 ekor hasil tangkapan pukat cincin yang didaratkan di Pelabuhan Sibolga. Contoh ikan dikumpulkan secara bulanan dari bulan Juli 2012 hingga Februari 2013. Pendugaan parameter dilakukan menggunakan program FISAT II (FAO-ICLARM Stock Assessment Tools). Hasil kajian menunjukkan kisaran panjang cagak antara 30 - 60 cm, panjang asimptotik (L∞)= 63,5 cm, laju pertumbuhan(K) = 0,63/tahun dan umur teoritis pada saat panjang ke 0 ( t0 ) = -0,21 tahun. Estimasi laju kematian total tahunan (Z) sebesar 2,40/tahun, laju kematian alami (M) sebesar 1,07/tahun dan laju kematian akibat penangkapan(F) sebesar 1,33/tahun. Perkiraan Laju eksploitasi (E) = 0,55 mengindikasikan bahwa tingkat pemanfaatan berada pada tingkat yang moderat.Kawakawa (Euthynnus affinis Cantor, 1849) is the one of the major catch of fishermen in the Indian Ocean west off Sumatera. This study was aimed to investigate data and information on growth, mortality and the exploitation rates of kawakawa. Analyses were carried out based on a number of 1,325 length frequency data from purse seine fishery landed in Sibolga Fishing Port. Monthly base data were collected from July 2012 to February 2013. The specimens ranged from 30 to 60 cm FL. parameters were determined through a packageprogramof FISAT II (FAO-ICLARM StockAssessment Tools). The result showed that asymptotic length (L∞) were 63.5 cmFL, growth rates (K) 0.63/yr and estimated t0 -0.21 years. The annual instantaneous rate of total mortality (Z) was 2.40/yr, the natural mortality (M) was 1.07/yr and the fishing mortality (F) was 1.33/yr. The exploitation rate (E = 0.55) indicated that E. affinis was moderately exploited in the area.

scholarly journals Mortality and exploitation rate of some reef fish in Ternate Island Waters

2021 ◽  
Vol 890 (1) ◽  
pp. 012061
Author(s):  
F Rumagia ◽  
B Kaidati ◽  
Darmawaty ◽  
K Nisaa
Keyword(s):  
Coastal Area ◽  
Stock Assessment ◽  
High Growth ◽  
Reef Fishes ◽  
Assessment Method ◽  
Population Increase ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Study Results ◽  
Exploitation Rate

Abstract Fish population dynamics are determined by the balance between population increase resulted from growth and addition of new individuals (recruitment), and population decrease due to fishing mortality and natural mortality. It is important to understand fish resources condition, including their change pattern caused by pressures on coral reef fisheries resource in coastal area of Ternate Island. This research aimed to analyze mortality and exploitation rate of several reef fishes that caught at coastal area of Ternate Island. Stock assessment method was used to determine the mortality and exploitation rate of some reef fishes. Study results showed that the fishing mortality of the sample species was lower than their natural mortality, while the exploitation rate results also showed the same condition those found in mortality rate, where the fish with high growth coefficient tended to have high mortality rates.

scholarly journals Preliminary observation on the sustainability of white sardine, Escualosa thoracata (Valenciennes, 1847), exploited from the central west coast of India

2021 ◽  
Vol 82 (1) ◽  
Author(s):  
Udai R. Gurjar ◽  
Suman Takar ◽  
Milind S. Sawant ◽  
Ravindra A. Pawar ◽  
Vivek H. Nirmale ◽  
...  
Keyword(s):  
West Coast ◽  
Total Mortality ◽  
Fishing Mortality ◽  
High Demand ◽  
Instantaneous Rate ◽  
Growth Coefficient ◽  
Domestic Markets ◽  
West Coast Of India ◽  
Exploitation Rate ◽  
Size Groups

Abstract Background The present study assessed the growth and mortality parameters of the white sardine, Escualosa thoracata which is having high local demand. The white sardine gained importance due to its taste, and high demand in domestic markets as compared to the oil sardine necessitated a study on this resource to know the present status of exploitation level along the central west coast of India. Results A total of 3026 individuals of different size groups of E. thoracata were randomly collected from the Burondi fish landing center of the Ratnagiri district of Maharashtra. The asymptotic length (L∞) and growth coefficient (K) were estimated to be 115 mm and 1.9 year−1, respectively, by ELEFAN-I and 135 mm and 1.2 year−1 by the scattergram. The value of t0 by von Bertalanffy plot was estimated to be −0.000012 year. The fish attained a length of 65 mm, 94 mm, and 114 mm at the end of 0.5, 1, and 1.5 years of its life, respectively. The instantaneous rate of total mortality (Z), natural mortality (M), and fishing mortality (F) were estimated to be 8.07 year−1, 2.55 year−1, and 5.52 year−1, respectively. The exploitation rate (U) was calculated as 0.65, and the exploitation ratio (E) was 0.68. Conclusion The growth, mortality, and other population parameters observed in the present study will help to understand the current stock status, which is pointing toward the over-fishing condition (E ˃ 0.50) of the white sardine in the study area. Therefore, the present investigation suggests reducing the fishing pressure on E. thoracata along the central west coast of India for the sustainability of the resource.

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