scholarly journals Stock assessment of the Indian mackerel Rastrelliger kanagurta (Cuvier, 1817) from Muscat coast, Oman

2016 ◽  
Vol 63 (4) ◽  
Author(s):  
N. Jayabalan ◽  
S. Zaki ◽  
A. Al-Marzouqi ◽  
F. Al-Kiyumi
Keyword(s):  
Stock Assessment ◽  
Total Mortality ◽  
B Value ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Indian Mackerel ◽  
A Value ◽  
Annual Total ◽  
Rastrelliger Kanagurta ◽  
Relationship Of

Assessment of age, growth and stock parameters was carried out for the Indian mackerel Rastrelliger kanagurta (Cuvier) along the Muscat coast of Oman between October 2007 and September 2009. The length-weight relationship of the fish indicated the ‘a’ value as 0.0101 and ‘b’ value as 3.0589. The length based von Bertalanffy growth (VBG) parameters L∞ K and t0 estimated were 37.54 cm, 1.0 y-1 and -0.17 y respectively. The estimates of mortality rates showed the annual total mortality (Z) to be 2.98, the natural mortality (M) 1.62 and fishing mortality (F) 1.36. The MSY estimated by Cadima’s estimator was 859 t and the predicted value by yield analysis stood at 1,273 t. The calculated exploitation rate (E) was 0.46. The Yw/R at F = 1.6 was 48 g. Estimates of higher MSY than the current yield, lower fishing mortality than natural mortality and lower E indicate scope for increase in yield of R. kanagurta from Muscat region.

scholarly journals DISTRIBUSI UKURAN PANJANG DAN PARAMETER POPULASI LOBSTER LUMPUR (Panulirus polyphagus Herbst, 1793) DI PERAIRAN SEBATIK, KALIMANTAN UTARA (WPPNRI-716)

2018 ◽  
Vol 1 (1) ◽  
pp. 11
Author(s):  
Umi Chodrijah ◽  
Asep Priatna ◽  
Duto Nugroho
Keyword(s):  
Spiny Lobster ◽  
Total Mortality ◽  
Management Plan ◽  
Population Parameter ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Stock Status ◽  
Annual Total ◽  
Biological Aspects ◽  
Average Size

Sumberdaya udang barong lumpur (Panulirus polyphagus Herbst, 1793) atau dalam bahasa lokal dikenal sebagai lobster Pakistan telah dimanfaatkan sebagai salah satu komoditas yang bernilai ekonomis di perairan pulau Sebatik, Kalimantan Utara. Data statistik perikanan menunjukkan produksi udang barong di perairan Timur Kalimantan tahun 2005 – 2015 meningkat pesat dengan kelipatan 10 kalinya. Terkait dengan fenomena tersebut, penelitian tentang aspek biologi populasi telah dilakukan pada bulan Maret sampai dengan November 2016. Penelitian ini bertujuan untuk mendapatkan parameter populasi sebagai landasan untuk mengetahui status stok pada tingkat pemanfaatan terkini. Hasil penelitian menunjukkan udang betina tertangkap pada ukuran rata-rata 86,9+ 8,58 mmCL sedangkan udang jantan pada ukuran 81,5 + 9,63 mmCL. Pola pertumbuhan udang jantan dan betina bersifat allometrik negatif (b<3). Estimasi panjang asimtotis (CL) sebesar 124,1 mm dengan laju pertumbuhan (K) 0,598/tahun. Rata-rata ukuran pertama tertangkap (CLc) adalah 84,5 mmCL. Nilai tersebut lebih rendah dari pertama kali matang gonad (CLm) sebesar 90,74 mmCL. Laju kematian total (Z) sebesar 2,26/tahun, laju kematian alamiah (M) 0,87/tahun serta laju kematian akibat penangkapan (F) 1,39/tahun. Estimasi laju eksploitasi cenderung mengarah kepada penangkapan berlebih (E = 0,61), oleh karena itu perlu dilakukan tindakan pengelolaan melalui pendekatan pengendalian upaya penangkapan dan pembatasan ukuran minimum yang boleh ditangkap. Mud spiny lobster (Panulirus polyphagus Herbst, 1793) or locally known as Pakistan lobster has been exploited as an important economic species in the waters of Sebatik Island, North Kalimantan. The best available capture fisheries statisticon 2005-2015 indicates the production of marine lobster were significantly increased by 10. Based on this phenomenon, observations on biological aspects were carried out during period of March to November 2016. The aim of this study were to estimate of stock status under existing fisheries condition. The result showed that the average size of females was 86.9+ 8.58 cmCL and males was 81.5 + 9.63 mmCL. The growth pattern indicates allometric negative (b<3). Population parameter performed by length based analysis indicates that asymptotic length (CL) was 124.1 mmCL with growth rate (K) of 0.598/yr.The average size of first capture (Lc) was estimated at 84.5 mmCL. This value was less than average size of first mature (CLm) of 90.7 cmCL.The predicted annual total mortality rates (Z) was 2.26/yr, the natural mortality (M) was 0.87/yr, and fishing mortalities (F) was 1.39/yr. The exploitation rates (E) of 0.61 tend to be beyond the sustainable exploitation level. To reduce the fishing mortality, the initiative of specific local management plan on restructuring active fleet and establishing minimum legal size should be implemented. 

scholarly journals SOME BIOLOGICAL STOCK INDICATORS OF BULLET TUNA (Auxis rochei, Risso 1810) FROM BANDA SEA AND ITS ADJACENT WATERS

2019 ◽  
Vol 25 (2) ◽  
pp. 103
Author(s):  
Khairul Amri ◽  
Afrisa Novalina ◽  
Bram Setyadji
Keyword(s):  
Sex Ratio ◽  
Stock Assessment ◽  
Total Mortality ◽  
Maximum Level ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Current Effort ◽  
Important Species ◽  
Male And Female ◽  
Mature Fish

Bullet tuna is considered as one of the important species for tuna purse seine fisheries in Indonesia, especially in archipelagic waters. However, little is known about its biological characteristics which proven to be pivotal in stock assessment. The purpose of this research was to determine some of the biological stock indicators for bullet tuna (Auxis rochei) from Banda Sea and its adjacent waters. The study was conducted from February to November 2016. The length of the bullet tuna caught were in between 18.5-32.7 cmFL (mode=24 cmFL). Growth pattern was isometric with b=3.01 and R2=0.84 Sex ratio was balanced between male and female (1:1). The spawning season allegedly from June to November. The length at 50% mature (L50) was 23.6 cmFL. A good indicator for the fisheries, where at least 75% of the mature fish caught were already spawned. The asymptotic length (L) was 33.63 cmFL, with coefficient of growth (K) around 0.73/year. Natural mortality (M) estimated at 1.87/year, fishing mortality (F) estimated at 2.20/year and total mortality (Z) was 4.07/year. The exploitation level (E) was estimated to be at maximum level (E=0.54/year), for precautionary purpose, the number of efforts should be reduced down to 8% from current effort. 

In what direction should the fishing mortality target change when natural mortality increases within an assessment?

2016 ◽  
Vol 73 (3) ◽  
pp. 349-357 ◽  
Author(s):  
Christopher M. Legault ◽  
Michael C. Palmer
Keyword(s):  
Mortality Rate ◽  
Empirical Evidence ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Total Mortality ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Limanda Ferruginea ◽  
Trade Offs

Traditionally, the natural mortality rate (M) in a stock assessment is assumed to be constant. When M increases within an assessment, the question arises how to change the fishing mortality rate target (FTarget). Per recruit considerations lead to an increase in FTarget, while limiting total mortality leads to a decrease in FTarget. Application of either approach can result in nonsensical results. Short-term gains in yield associated with high FTarget values should be considered in light of potential losses in future yield if the high total mortality rate leads to a decrease in recruitment. Examples using yellowtail flounder (Limanda ferruginea) and Atlantic cod (Gadus morhua) are used to demonstrate that FTarget can change when M increases within an assessment and to illustrate the consequences of different FTarget values. When a change in M within an assessment is contemplated, first consider the amount and strength of empirical evidence to support the change. When the empirical evidence is not strong, we recommend using a constant M. If strong empirical evidence exists, we recommend estimating FTarget for a range of stock–recruitment relationships and evaluating the trade-offs between risk of overfishing and forgone yield.

scholarly journals Population Dynamics and Stock Assessment of Gudusia chapra (Hamilton-Buchanan) in the Rajdhala Reservoir, Netrakona, Bangladesh

2007 ◽  
Vol 19 (3) ◽  
Author(s):  
M. A. RAHMAN ◽  
M. M. HAQUE
Keyword(s):  
Population Dynamics ◽  
Growth Parameters ◽  
Stock Assessment ◽  
Total Mortality ◽  
Maximum Sustainable Yield ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Length Frequency ◽  
Recruitment Pattern ◽  
Pattern Maximum

Population dynamics and stock assessment of chapila (Gudusia chapra, Hamilton-Buchanan) in the Rajdhala reservoir, Netrakona, Bangladesh was studied from January 2003 to December 2004 using length-frequency based analysis of FiSAT software to evaluate the growth parameters, mortality rates, exploitation rates, recruitment pattern, maximum sustainable yield (MSY) and the corresponding fishing mortality at this level. The annual rates of natural mortality, fishing mortality and total mortality were 1.34, 1.37 and 2.71 yr-1 in 2003 and 1.37, 1.58 and 2.95 yr-1 in 2004 respectively. The study revealed that the fishes were recruited in the fishery twice a year and the fishes were harvested at a higher level than the optimum fishing pressure. Twenty four percent of the present exploitation pressure on chapila is suggested to be reduced to get the MSY of this fish from the reservoir.

scholarly journals An integrated tagging model to estimate mortality rates of Albemarle Sound – Roanoke River striped bass

2017 ◽  
Vol 74 (7) ◽  
pp. 1061-1076 ◽  
Author(s):  
Julianne E. Harris ◽  
Joseph E. Hightower
Keyword(s):  
Striped Bass ◽  
Stock Assessment ◽  
Mortality Rates ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Albemarle Sound ◽  
High Reward ◽  
Accuracy And Precision ◽  
Summer Mortality ◽  
Roanoke River

We developed an integrated tagging model to estimate mortality rates and run sizes of Albemarle Sound – Roanoke River striped bass (Morone saxatilis), including (i) a multistate component for telemetered fish with a high reward external tag; (ii) tag return components for fish with a low reward external or PIT tag; and (iii) catch-at-age data. Total annual instantaneous mortality was 1.08 for resident (458–899 mm total length, TL) and 0.45 for anadromous (≥900 mm TL) individuals. Annual instantaneous natural mortality was higher for resident (0.70) than for anadromous (0.21) fish due to high summer mortality in Albemarle Sound. Natural mortality for residents was substantially higher than currently assumed for stock assessment. Monthly fishing mortality from multiple sectors (including catch-and-release) corresponded to seasonal periods of legal harvest. Run size estimates were 499 000–715 000. Results and simulation suggest increasing sample size for the multistate component increases accuracy and precision of annual estimates and low reward tags are valuable for estimating monthly fishing mortality rates among sectors. Our results suggest that integrated tagging models can produce seasonal and annual mortality estimates needed for stock assessment and management.

scholarly journals POPULATION DYNAMICS OF MALAYAN LEAF FISH (Pristolepisgrooti Blkr.) IN RANAU LAKE, SOUTH SUMATRA

2018 ◽  
Vol 24 (2) ◽  
pp. 125
Author(s):  
Sevi Sawetri ◽  
Subagdja Subagdja ◽  
Dina Muthmainnah
Keyword(s):  
Mortality Rate ◽  
Growth Parameters ◽  
Total Mortality ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Frequency Data ◽  
Length Frequency ◽  
Lake Ecosystems ◽  
Exploitation Rate ◽  
Length Frequency Data

The Malayan leaf fish or locally named as kepor (Pristolepis grooti) is one of important biotic components in Ranau Lake ecosystems. This study aimed to estimate population dynamic and exploitation rate of kepor in Ranau Lake, South Sumatera. The population parameters are estimated based on length frequency data which were collected in March to October 2013. Growth parameters and fishing mortality rates were calculated using FiSAT software package. The results showed that kepor’s growth was negative allometric, which tended to gain length faster than weight. Kepor population was dominated (42%) by individual length of 10.0 to 11.0 cm. Predicted length infinity (L) was 17.28 cm with high value of growth rates (K) of 1.4 year-1. The natural mortality rate (M) is 2.57 year-1, the fishing mortality rate (F) is 5.36 year-1 and total mortality rate (Z) is 7.93 year-1. The exploitation rate of Malayan leaf fish in Ranau Lake (E = 0.68 year-1) has passed the optimum score.  

Population dynamics and stock assessment of Hilsa shad, Tenualosa ilisha (Hamilton, 1822) along the coast of Bangladesh

2021 ◽  
Vol 48 (2) ◽  
pp. 231-241
Author(s):  
Md Khairul Islam ◽  
Md Humayun ◽  
Manmatha Nath Sarker ◽  
Md Sharifuddin ◽  
M Niamul Naser
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Population Analysis ◽  
Total Mortality ◽  
Maximum Sustainable Yield ◽  
Fishing Mortality ◽  
Recruitment Pattern ◽  
Weight Relationship ◽  
Tenualosa Ilisha ◽  
Highly Correlated

Stock Assessment of Tenualosa ilisha (Hamilton, 1822) were estimated using FiSAT-II software with length-frequency data collected from different landing centers. The Southeast Coast of Bay Of Bengal, Cox's Bazar. The Von Bertalanffy growth parameters Land K for the species were asymptotic length (L∞) was 51.41 cm, growth rate (K) was 0.75 year-1 and t0 = -0.2 year respectively. The estimated value of total mortality (Z) based on length converted catch curve using these growth parameters was 2.35 year-1.Natural mortality (M) based on growth parameters and mean environmental temperature (T = 27° C) was 1.00 year-1 and fishing mortality (F) was 1.35 year-1. Optimum length of hilsa at first capture (Lc=L50) was 28.36 cm TL. Growth performance indices (ϕ') was 3.30. The estimated value of the exploitation rate (E) using the length-converted catch curve was 0.57. The recruitment pattern of this species was continuous and two peaks per year. The present investigation clearly showed the over fishing (E > 0.50) condition for T. ilisha in Bangladesh. The estimated length-weight relationship for the combined sex was found to be W = 0.0109 L3. Virtual population analysis (VPA) showed that the maximum fishing mortality occurring in the length between 30 to 35 cm with a maximum value in the length of 32 cm that repeatedly indicate high fishing mortality in the T. ilisha. The generalized length-weight relationship was fitted with the pooled data of all monthly samples were BW = 0.029 TL2.718 (R2= 0.833) respectively. The results revealed that all length-weight relationships were highly correlated (r > 0.993). Maximum sustainable yield (MSY) was estimated as 435,554 t. Bangladesh J. Zool. 48(2): 231-241, 2020

Detecting mortality variation to enhance forage fish population assessments

2018 ◽  
Vol 76 (1) ◽  
pp. 124-135 ◽  
Author(s):  
Nis S Jacobsen ◽  
James T Thorson ◽  
Timothy E Essington
Keyword(s):  
Test Performance ◽  
Size Structure ◽  
Stock Assessment ◽  
Reference Points ◽  
Forage Fish ◽  
Natural Mortality ◽  
Time Varying ◽  
Fishing Mortality ◽  
Catch Data ◽  
Over Time

Abstract Contemporary stock assessment models used by fisheries management often assume that natural mortality rates are constant over time for exploited fish stocks. This assumption results in biased estimates of fishing mortality and reference points when mortality changes over time. However, it is difficult to distinguish changes in natural mortality from changes in fishing mortality, selectivity, and recruitment. Because changes in size structure can be indicate changes in mortality, one potential solution is to use population size-structure and fisheries catch data to simultaneously estimate time-varying natural and fishing mortality. Here we test that hypothesis, using a simulation experiment to test performance for four alternative estimation models that estimate natural and fishing mortality from size structure and catch data. We show that it is possible to estimate time-varying natural mortality in a size-based model, even when fishing mortality, recruitment, and selectivity are changing over time. Finally, we apply the model to North Sea sprat, and show that estimates of recruitment and natural mortality are similar to estimates from an alternative multispecies population model fitted to additional data sources. We recommend exploring potential trends in natural mortality in forage fish assessments using tools such as the one presented here.

scholarly journals Time-varying natural mortality in fisheries stock assessment models: identifying a default approach

2014 ◽  
Vol 72 (1) ◽  
pp. 137-150 ◽  
Author(s):  
Kelli F. Johnson ◽  
Cole C. Monnahan ◽  
Carey R. McGilliard ◽  
Katyana A. Vert-pre ◽  
Sean C. Anderson ◽  
...  
Keyword(s):  
Stock Assessment ◽  
Assessment Method ◽  
Reference Points ◽  
Natural Mortality ◽  
Time Varying ◽  
Fishing Mortality ◽  
Total Allowable Catch ◽  
Robust Approach ◽  
Structured Population Models ◽  
Trade Offs

Abstract A typical assumption used in most fishery stock assessments is that natural mortality (M) is constant across time and age. However, M is rarely constant in reality as a result of the combined impacts of exploitation history, predation, environmental factors, and physiological trade-offs. Misspecification or poor estimation of M can lead to bias in quantities estimated using stock assessment methods, potentially resulting in biased estimates of fishery reference points and catch limits, with the magnitude of bias being influenced by life history and trends in fishing mortality. Monte Carlo simulations were used to evaluate the ability of statistical age-structured population models to estimate spawning-stock biomass, fishing mortality, and total allowable catch when the true M was age-invariant, but time-varying. Configurations of the stock assessment method, implemented in Stock Synthesis, included a single age- and time-invariant M parameter, specified at one of the three levels (high, medium, and low) or an estimated M. The min–max (i.e. most robust) approach to specifying M when it is thought to vary across time was to estimate M. The least robust approach for most scenarios examined was to fix M at a high value, suggesting that the consequences of misspecifying M are asymmetric.

Integrating catch-at-age and multiyear tagging data: a combined Brownie and Petersen estimation approach in a fishery context

2006 ◽  
Vol 63 (3) ◽  
pp. 534-548 ◽  
Author(s):  
Tom Polacheck ◽  
J Paige Eveson ◽  
Geoff M Laslett ◽  
Kenneth H Pollock ◽  
William S Hearn
Keyword(s):  
Mortality Rate ◽  
Population Size ◽  
Stock Assessment ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Catch Data ◽  
Coefficients Of Variation ◽  
Southern Bluefin Tuna ◽  
Catch Rates ◽  
Comprehensive Framework

A comprehensive framework for modelling data from multiyear tagging experiments in a fishery context is presented that incorporates catch data into the traditional Brownie tag–recapture model. Incorporation of catch data not only allows for improved estimation of natural and fishing mortality rates, but also for direct estimation of population size at the time of tagging. These are the primary quantities required to be estimated in stock assessments — having an approach for directly estimating them that does not require catch rates provides a potentially powerful alternative for augmenting traditional stock assessment methods. Simulations are used to demonstrate the value of directly incorporating catch data in the model. Results from the range of scenarios considered suggest that in addition to providing a precise estimate of population size (coefficients of variation ranging from ~15% to 30%), including catch data can decrease biases in the mortality rate estimates (natural mortality especially) and improve precision of fishing mortality rate estimates (by as much as 60% at age 1). The model is applied to southern bluefin tuna (Thunnus maccoyii) tag–recapture and catch data collected in the 1990s to provide estimates of natural mortality, fishing mortality, and abundance for five cohorts of fish.

Sign in / Sign up

Export Citation Format

Share Document