Which community indicators can measure the impact of fishing? A review and proposals

2003 ◽  
Vol 60 (1) ◽  
pp. 86-99 ◽  
Author(s):  
Marie-Joëlle Rochet ◽  
Verena M Trenkel
Keyword(s):  
Average Length ◽  
Total Mortality ◽  
Diversity Indices ◽  
Reference Points ◽  
Size Spectra ◽  
Expected Effect ◽  
Piscivorous Fish ◽  
Exploitation Rate ◽  
Species Abundances ◽  
The Impact

Population and community descriptors that might be used as indicators of the impact of fishing are reviewed. The criteria used for the evaluation of these indicators are meaning, expected effect of fishing, exclusiveness to fishing effects, and measurability. Population indicators such as total mortality rate, exploitation rate, or average length are the most operational indicators because their meaning is clear and the expected effect of fishing on them is well understood so that reference points can be set. On the other hand, indicators based on the composition of species assemblages such as diversity indices and ordination of species abundances are difficult to interpret, and the effect of fishing on them is not easily predicted. Robust indicators describing the community functions of interest (production and transfer of biomass to large fish), such as size spectra descriptors or the proportion of piscivorous fish in the community, are more promising but are not yet well developed. New candidate indicators are proposed: the change in fishing mortality required to reverse population growth rate, the proportion of noncommercial species in the community, and the average length and weight in the community.

Performance of indicators derived from abundance estimates for detecting the impact of fishing on a fish community

2003 ◽  
Vol 60 (1) ◽  
pp. 67-85 ◽  
Author(s):  
Verena M Trenkel ◽  
Marie-Joëlle Rochet
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Statistical Power ◽  
Total Mortality ◽  
Reference Points ◽  
Partial Dominance ◽  
Community Indicators ◽  
Abundance Estimates ◽  
Exploitation Rate ◽  
The Impact

Population and community indicators for the impact of fishing are often estimated using abundance estimates instead of raw sampling observations. Methods are presented for testing null hypotheses of nonsignificant impacts and, where possible, for calculating the statistical power. The indicators considered concern populations (intrinsic growth rate, total mortality, exploitation rate, and a new indicator, the change in fishing mortality required to reverse population growth) and communities (k- and partial-dominance curves, a biodiversity index, size spectrum, and proportions of various population groups). The performance of these indicators is compared for the Celtic Sea groundfish community based on achieved precision, statistical power, and availability and estimation method of reference points. Among population indicators, mean length of catch was most precisely estimated and the corresponding hypothesis tests had consistently large powers. Total mortality performed reasonably well. In contrast, both the intrinsic population growth rate and the exploitation rate gave unreliable results. All tested community indicators performed similarly well. Indicators for which the direction of change caused by fishing is predictable, such as the proportion of noncommercial species or piscivores in the community, are promising indicators at the community level.

scholarly journals Population parameters of the pontic shad, Alosa immaculata Bennett, 1835 in the Fatsa coast of the south-eastern Black Sea

2019 ◽  
Vol 36 (4) ◽  
pp. 319-324
Author(s):  
İsmet Balık
Keyword(s):  
Black Sea ◽  
Maximum Yield ◽  
Total Mortality ◽  
Reference Points ◽  
Growth Equation ◽  
Fishing Mortality ◽  
Population Parameters ◽  
The South ◽  
South Eastern ◽  
Exploitation Rate

The aim of this study is to estimate population parameters of pontic shad, Alosa immaculata Bennett, 1835 in the Fatsa coast of the south-eastern Black Sea. A total of 314 pontic shad specimens were collected from study area using artisanal fishing gears from March 2013 to February 2014. In the study, parameters of the von Bertalanffy growth equation were found as L∞=43.05 cm; k=0.430 per year and t0=-0.451 year. The growth performance index (Φ') was estimated as 2.90. The total mortality (Z), natural mortality (M), fishing mortality rates (F) were calculated as 1.33 year-1, 0.75 year-1 and 0.58 year-1, respectively. The annual instantaneous fishing mortality rate was greater than both the target (Fopt=0.375 year-1) and limit (Flimit=0.50 year-1) biological reference points. Similarly, the present level of exploitation rate (E=0.43) was higher than the exploitation ratio for maximum yield per recruit (Emax=0.375) suggesting that overexploitation occurred. These results showed that this species has been over-exploited in the Fatsa coast of the south-eastern Black Sea. Measures should be taken to reduce the current exploitation rate for sustainable fishing of pontic shad in the Fatsa coast of the south-eastern Black Sea.

scholarly journals Population Dynamics of Reba Carp Cirrhinus Reba From Indus River, Sukkur, Sindh, Pakistan

2020 ◽  
Vol 48 (1) ◽  
pp. 81-91
Author(s):  
Khadim Hussain Memon ◽  
Rashida Bhanbhro ◽  
Qun Liu ◽  
Tahira Jabeen Ursani ◽  
Abdul Manan Shaikh ◽  
...  
Keyword(s):  
Growth Parameters ◽  
Average Length ◽  
Minimum Weight ◽  
Total Mortality ◽  
Reference Points ◽  
Minimum Length ◽  
Average Weight ◽  
Fishing Mortality ◽  
Indus River ◽  
Strategic Plans

Present work was done from Indus River, Sukkur, Sindh, Pakistan to evaluate the present stock of Cirrhinus reba Suhni (Reba carp) for first time. Since the assessment of stocks deliver the important knowledge of stocks of commercially important fish species to the fisheries managers to make better strategic plans for sustainable exploitation. Data based on length-frequency was obtained from October 2015 to March 2016, a total of 463 pairs of length-weight were measured. Minimum length was measured to 13cm, maximum length was 29cm and the average length of 17cm was measured with minimum weight of 15g, maximum weight of224g and67g was the average weight. Obtained results of length-weight relationship were R2 = 0.817, a = 0.037 and b = 2.557. Growth parameters were computed as L∞= 29.40 cm and= 0.240 year-1using ELEFAN method in FISAT computer package. Growth performance index (∅′) was calculated as ∅′ = 2.317 year-1 Total mortality Z, natural mortality M and fishing mortality F was estimated as= 0.630 year-1, M= 0.617 year-1 and F=0.012 year-1 respectively. Using (E = F/Z) the exploitation ratio was obtained as E=0.019 year-1 Current fishing mortality rate of 0.012 was smaller than the target biological reference points (Fopt) of M (0.617). While MSY was recorded as; 8.144 tonsyear-1 which showed the higher results than 0.031 tons year-1ofcurrent catch. This study concluded that the C. reba confronting poor health though the stocks found not to be overexploited in the region. Bangladesh J. Zool. 48(1): 81-91, 2020

scholarly journals Population dynamics of Sardinella aurita (Val., 1847) within Ghana’s coastal waters

2017 ◽  
Vol 4 (3) ◽  
pp. 237-248
Author(s):  
Samuel KK Amponsah ◽  
Patrick K Ofori Danson ◽  
Francis KE Nunoo ◽  
Godfred A Ameyaw
Keyword(s):  
Mortality Rate ◽  
Coastal Waters ◽  
Total Mortality ◽  
Mesh Size ◽  
Reference Points ◽  
Recruitment Pattern ◽  
Commercial Fish ◽  
Management Interventions ◽  
Exploitation Rate ◽  
Sardinella Aurita

Following the declining stocks of Sardinella aurita within the coastal waters of Ghana, this study aimed at examining some population parameters of Sardinella aurita as a guide for managing this important stock sustainably. Length-frequency data of 717 samples were obtained from June, 2014 to January 2015 and measured for total length with the resultant data analyzed using FiSAT II. The asymptotic length (L∞) and growth rate (K) were 21.53 cm SL and 0.25yr-1 respectively. The theoretical age at birth (t0), longevity (tmax) and growth performance index (ϕ) were -0.74yr-1, 12 years and 1.849 respectively. Total mortality rate (Z), natural mortality rate (M) and fishing mortality rate (F) were 3.17, 0.76 and 2.41yr-1 respectively. The ages at first recruitment and first capture signaled future collapse of the stock, in the absence of proper management interventions. VPA outcome showed that mid- lengths of 11 cm and 12 cm SL experienced the highest harvesting rate with MSY estimated at 7733 tons. The recruitment pattern was continuous with two major recruitment pulses. Exploitation rate (Ecurr=0.76) was higher than the maximum exploitation rate (Emax=0.56), indicating unsustainable exploitation. Further, the fishing regime fell within the overfished stage based on the Quadrant Rule. For sustainable exploitation of this commercial fish species, implementation of relevant biological reference points through reduction in fishing efforts, creation of marine protected areas and mesh size regulation are urgently advocated.Res. Agric. Livest. Fish.4(3): 237-248, December 2017

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 Aspects of Population Dynamics of Tiger Tooth Croaker, Otolithes ruber (Bloch and Schneider, 1801) from Northwest Arabian Gulf, Iraq

2021 ◽  
pp. 9-21
Author(s):  
Abdul-Razak M. Mohamed ◽  
Ali H. Al-Hassani
Keyword(s):  
Population Dynamics ◽  
Population Analysis ◽  
Arabian Gulf ◽  
Relative Yield ◽  
Total Mortality ◽  
Reference Points ◽  
Virtual Population Analysis ◽  
Virtual Population ◽  
Exploitation Rate ◽  
Otolithes Ruber

The present study consists of the growth, mortality, relative yield recruit and virtual population analysis of tigertooth croaker, Otolithes ruber from Iraqi marine waters, northwest Arabian Gulf between February 2020 and January 2021. Analysis of population dynamics employed methods fitted in FiSAT II software using pooled length-frequencies. A total of 3835 individuals of O. ruber ranged from 17.0 to 60.0 cm have been collected. The exponent (b) of the length-weight relationship was found to be 2.755. The von Bertalanffy growth parameters (L∞ and K) were estimated as 68.5 cm and 0.36, respectively, while the growth performance index (Ø') was 3.228.  The total mortality (Z) was calculated as 1.10, while the natural and fishing mortality rates were 0.69 and 0.41, respectively, and the current exploitation rate (Ecurrent) was 0.38. Fish were recruited to the fishery at a mean size of L50= 20.55 cm. The recruitment pattern of O. ruber was continuous throughout the year with two major peaks. The analysis of yield-per-recruit (Y/R’) indicates that the current exploitation rate was below the biological target reference points (E0.1 = 0.40 and Emax= 0.53), refer to the stock of O. ruber is underexploited. The 27 cm length group was more vulnerable to fishing and more harvested according to virtual population analysis. sLength at first capture was higher than the length at first maturity of the species in the region. For management purposes, more yields could be obtained by increasing the mesh sizes of the nets employed in the fishing of 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 PARAMETER POPULASI IKAN BAWAL PUTIH (Pampus argenteus) DI PERAIRAN TARAKAN, KALIMANTAN TIMUR

2015 ◽  
Vol 7 (3) ◽  
pp. 165
Author(s):  
Prihatiningsih Prihatiningsih ◽  
Nurainun Mukhlis ◽  
Sri Turni Hartati
Keyword(s):  
Frequency Analysis ◽  
Average Length ◽  
Total Mortality ◽  
Assessment Tools ◽  
Growth Equation ◽  
Population Parameters ◽  
Length Frequency ◽  
Pampus Argenteus ◽  
Exploitation Rate ◽  
Length Frequency Analysis

Ikan bawal putih (Pampus argenteus) mempunyai nilai ekonomis penting dan sebagai salah satu komoditas unggulan di perairan Tarakan. Informasi tentang biologi perikanan ikan tersebut masih terbatas. Penelitian ini bertujuan untukmengestimasi parameter populasi meliputi pertumbuhan, umur, mortalitas dan tingkat eksploitasi ikan bawal putih. Data frekuensi panjang bulanan dikumpulan pada Februari – Nopember 2013 dengan bantuan enumerator. Sebaran frekuensi panjang ikan dipisahkan kedalam sebaran normal menggunakan metode Bhattacharya pada progran FiSAT (FAO-ICLARM Stock Assessment Tools). Estimasi parameter populasi dengan aplikasi model analitikmenggunakan program ELEFAN-1 (Electronic Length Frequency Analysis). Hasil penelitian menunjukkan ukuran panjang ikan bawal putih berkisar antara 9,0 cm–35,0 cmFL. Hubungan panjangberat ikan bawal putih yang tertangkap dengan jaring insang bersifat allometrik negatif mengikuti persamaan W= 0,187L2,374. Nilai rata-rata panjang ikan pada saat pertama kali tertangkap (Lc) sama dengan ukuran pertama kali matang gonad (Lm). Laju pertumbuhan (K) sebesar 0,52/tahun dan panjang asimptotik (L ) sebesar 37,28 cmFL. Persamaan pertumbuhan dari Von Bertalanffy sebagai Lt = 37,28 (1 – e-0,52(t-+0,07)). Mortalitas alami (M) adalah 1,11/tahun, mortalitas karena penangkapan (F) = ,65/tahun dan mortalitas total (Z) = 1,65/tahun. Laju pengusahaan (E) sebesar 0,60 berarti tingkat eksploitasinya sudah melebihi dari nilai optimal (E=0,5) atau populasi ikan bawal putih dalam keadaan lebih tangkap (over exploited). Untuk itu diperlukan kebijakan pengelolaan secara hati-hati dengan mempertimbangkan aspek biologi dan aspek penangkapan yang sedang berjalan.White pomfret (Pampus argenteus) is one of the economically important fish and includes leading commodity in Tarakan waters. Information of fishing biology of those species were still limited. This study aims to determine the population parameters including growth, age, mortality and exploitation rate of white pomfret. Monthly length frequency data have been collected by enumerator from February to November 2013. Fish lengthfrequency distribution was separated into a normal distribution using the Bhattacharya method with software of FiSAT (FAO-ICLARMStock Assessment Tools). Estimation of population parameters were use analytical model application with ELEFAN-1 (Electronic Length Frequency Analysis) program. The results showed that lengths distribution of white pomfret ranged beetwen 9.0 cm -35.0 cmFL. Length-weight relationship was negatively allometric. Estimating the average length at first captured (Lc) was equal with average length at first maturity (Lm) with growth equation of Lt = 37.28 (1 - e-0, 52 (t +0.07)). Natural mortality (M) was 1.11/year, fishing mortality (F) was 1.65/yearand total mortality (Z) was 1.65/ year. The exploitation rate (E) was 0.60. It is mean that more higher than optimal exploitation so that the white pomfret fish population in a state of over fished. It is necessary to better policy in the management of white pomfret through precaution approach and describing of biologycal and fishing aspect in Tarakan, Kalimantan Timur.

scholarly journals Times of change in complex environments - Evaluating hospital co-payments in Palestine refugee camps

2020 ◽  
Vol 30 (Supplement_5) ◽  
Author(s):  
S V Valente de Almeida ◽  
H Ghattas ◽  
G Paolucci ◽  
A Seita
Keyword(s):  
Length Of Stay ◽  
Policy Change ◽  
Negative Binomial ◽  
Negative Impact ◽  
Average Length ◽  
Lessons Learned ◽  
Policy Impact ◽  
Average Length Of Stay ◽  
Ex Post ◽  
The Impact

Abstract We measure the impact introducing a of 10% co-payment component on hospitalisation costs for Palestine refugees from Lebanon in public and private hospitals. This ex-post analysis provides a detailed insight on the direction and magnitude of the policy impact in terms of demand and supply for healthcare. The data was collected by the United Nations Relief and Works Agency for Palestine Refugees in the Near East and include episode level information from all public, private and Red Crescent Hospitals in Lebanon, between April 2016 and October 2017. This is a complete population episode level dataset with information from before and after the policy change. We use multinomial logit, negative binomial and linear models to estimate the policy impact on demand by type of hospital, average length of stay and treatment costs for the patient and the provider. After the new policy was implemented patients were 18% more likely to choose a (free-of-charge) PRCS hospital for secondary care, instead of a Private or Public hospital, where the co-payment was introduced. This impact was stronger for episodes with longer stays, which are also the more severe and more expensive cases. Average length of stay decreased in general for all hospitals and we could not find a statistically significant impact on costs for the provider nor the patient. We find evidence that the introduction of co-payments is hospital costs led to a shift in demand, but it is not clear to what extent the hospitals receiving this demand shift were prepared for having more patients than before, also because these are typically of less quality then the others. Regarding costs, there is no evidence that the provider managed to contain costs with the new policy, as the demand adapted to the changes. Our findings provide important information on hospitalisation expenses and the consequences of a policy change from a lessons learned perspective that should be taken into account for future policy decision making. Key messages We show that in a context of poverty, the introduction of payment for specific hospital types can be efficient for shifting demand, but has doubtable impact on costs containment for the provider. The co-payment policy can have a negative impact on patients' health since after its implementation demand increased at free-of-charge hospitals, which typically have less resources to treat patients.

scholarly journals What is the impact of multimorbidity on the risk of hospitalisation in older adults? A systematic review study protocol

BMJ Open ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. e049974
Author(s):  
Luciana Pereira Rodrigues ◽  
Andréa Toledo de Oliveira Rezende ◽  
Letícia de Almeida Nogueira e Moura ◽  
Bruno Pereira Nunes ◽  
Matias Noll ◽  
...  
Keyword(s):  
Systematic Review ◽  
Older Adults ◽  
Study Protocol ◽  
Average Length ◽  
Length Of Hospital Stay ◽  
Case Control Studies ◽  
Cross Sectional ◽  
Increased Risk ◽  
Review Study ◽  
The Impact

IntroductionThe development of multiple coexisting chronic diseases (multimorbidity) is increasing globally, along with the percentage of older adults affected by it. Multimorbidity is associated with the concomitant use of multiple medications, a greater possibility of adverse effects, and increased risk of hospitalisation. Therefore, this systematic review study protocol aims to analyse the impact of multimorbidity on the occurrence of hospitalisation in older adults and assess whether this impact changes according to factors such as sex, age, institutionalisation and socioeconomic status. This study will also review the average length of hospital stay and the occurrence of hospital readmission.Methods and analysisA systematic review of the literature will be carried out using the PubMed, Embase and Scopus databases. The inclusion criteria will incorporate cross-sectional, cohort and case–control studies that analysed the association between multimorbidity (defined as the presence of ≥2 and/or ≥3 chronic conditions and complex multimorbidity) and hospitalisation (yes/no, days of hospitalisation and number of readmissions) in older adults (aged ≥60 years or >65 years). Effect measures will be quantified, including ORs, prevalence ratios, HRs and relative risk, along with their associated 95% CI. The overall aim of this study is to widen knowledge and to raise reflections about the association between multimorbidity and hospitalisation in older adults. Ultimately, its findings may contribute to improvements in public health policies resulting in cost reductions across healthcare systems.Ethics and disseminationEthical approval is not required. The results will be disseminated via submission for publication to a peer-reviewed journal when complete.PROSPERO registration numberCRD42021229328.

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