Gillnet selectivity estimates for five commercially important fish species in Tono Reservoir, Northern Ghana

Akongyuure, Daniel Nsoh; Amisah, S.; Agyemang, Thomas Kwaku

doi:10.1111/lre.12188

Cited by 7 publications

(8 citation statements)

References 12 publications

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“…The desirable target would be to let as many fish as possible spawn at least once before they are caught, to rebuild and maintain healthy spawning stocks (Froese 2004). The total length at first sexual maturity was based on published research on the species (Adite and Van Thielen 1995, Akongyuure et al 2017b, Duponchelle and Panfili 1998, Kwarfo-Apegyah and Ofori-Danson 2010, Lederoun et al 2016, Ofori-Danson et al 2008.…”

Section: Relative Yield Per Recruit (Y'/r) and Reference Pointsmentioning

confidence: 99%

“…Research has mainly focused on fisheries socioeconomics, water productivity, sedimentation, and water storage, in particular at Tono (Abache 2015, Abubakari 2015, Diekkr€ uger and Liebe 2002, Mdemu 2008, Okrah 2010. Recent work on the Tono Reservoir by Akongyuure et al (2017b) was focused on gillnet selectivity estimates of the target fish species. Kwarfo-Apegyah (2008) studied the exploitation rates and management implications of the Bontanga Reservoir fisheries from 2004 to 2006 and reported that the reservoir had 26 fish species belonging to 19 genera in 11 families.…”

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confidence: 99%

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Assessing the exploitation status of main fisheries resources in Ghana’s reservoirs based on reconstructed catches and a length-based bootstrapping stock assessment method

Abobi

Mildenberger

Kolding

et al. 2019

Lake and Reservoir Management

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Assessing the exploitation status of main fisheries resources in Ghana's reservoirs based on reconstructed catches and a length-based bootstrapping stock assessment method. Lake Reserv Manage. 35:415-434. The cichlid species Oreochromis niloticus, Sarotherondon galilaeus, and Coptodon zillii, which are among the most exploited resources in the small-scale fisheries of the Tono, Bontanga, and Golinga reservoirs in northern Ghana, were assessed based on length frequency samples. Growth, mortality, exploitation status, stock size, and relative yield per recruit reference points were determined using bootstrapping fish stock assessment (BFSA), a novel framework that allows for the estimation of uncertainties around the life-history parameters and reference levels (e.g., L 1 , K, and F 0.1). The results suggest that the 3 species studied are heavily exploited in all 3 reservoirs, but with no alarming signs of overexploitation. The fishing effort at Golinga is comparatively low as a result of insignificant fishing during the agriculture season, which relates to low exploitation rates. Sarotherondon galilaeus and C. zillii have the highest and lowest biomass (t/km 2) respectively in all the 3 reservoirs. The small shallow reservoir (Golinga) has the highest biomass of the target resources per unit area. According to a second assessment approach, based on length-based indicators, all species at Bontanga and O. niloticus and S. galilaeus populations at Golinga have spawning stock biomasses below 40% of the unfished biomass. This points to a situation of a possible ongoing recruitment overfishing of those species in the 2 reservoirs and suggests that a further increase in fishing effort should be prevented. Further monitoring of these fisheries will be needed for the improvement of assessments and thus management advice.

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Section: Relative Yield Per Recruit (Y'/r) and Reference Pointsmentioning

confidence: 99%

mentioning

confidence: 99%

Assessing the exploitation status of main fisheries resources in Ghana’s reservoirs based on reconstructed catches and a length-based bootstrapping stock assessment method

Abobi

Mildenberger

Kolding

et al. 2019

Lake and Reservoir Management

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“…The optimum total lengths at capture of four of these fish species excluding C. zillii ranged from 13.53 to 25.43 cm using a 5‐centimeter (cm) gillnet and 18.95–35.60 cm using a 7‐cm gillnet. The mean total length at first sexual maturity for all five fish species ranged from 8.60 to 28.86 cm (Akongyuure, Amisah, & Agyemang, ).…”

Section: Methodsmentioning

confidence: 99%

Climate variability, water levels, and fish catch in the Upper East Region of Ghana

Abdul-Rahaman

Campion

Edziyie

2018

Environmental Quality Mgmt

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The aim of the research was to investigate the effects of climate variability on selected water bodies in the Upper East Region of Ghana using time series decomposition and simple linear regression analyses. Data on temperature and rainfall (1960–2015), annual total fish catch (1996–2016), and the recorded water levels (1987–2015) of a major reservoir, the Tono, were used. Time series decomposition analyses were performed on the rainfall, temperature, and water level data to identify their trends. While temperature was increasing, rainfall was decreasing and resulted in a decrease in the water level in the Tono Reservoir. The decreasing water level in the reservoir made fish catch easier, which led to overfishing. Out of the other 39 dugouts studied, 8 (21%) were silted. Also, rainfall was decreasing at 4.4% per decade and minimum and maximum temperatures were increasing at 2.5% and 0.03% per decade, respectively. The minimum, maximum, and mean water levels of the Tono Reservoir were 3.7, 8.0, and 4.9 meters (m), respectively. The water level of the Tono Reservoir was decreasing by −0.08 m per year. It is concluded that the water level in the Tono Reservoir was continually decreasing as a result of decreasing rainfall and increasing maximum and minimum temperatures. To maintain a much more stable microclimate and decrease the siltation rate of the reservoirs, farmers are advised to stop farming along the banks of water bodies and avoid clearing vegetation. Fishermen are also encouraged to adopt fish farming in enclosed areas within the reservoir to meet the growing protein demands in the Upper East Region of Ghana.

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“…The fishermen usually use the gill nets for catching little tuna, Indian mackerel, scad, sardines and other pelagic fishes. The gill nets are considered as environmentally friendly fishing gears and research on this gear continuous to be developed [1,[18][19][20][21]. The catch is usually directly marketed in the form of fresh fish.…”

Section: Characteristic Of Respondentsmentioning

confidence: 99%

Factors Affecting the Demand and Price Elasticity for Little Tuna in Kotabaru District, South Kalimantan, Indonesia

2021

JMSRO

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The research focused on factors affecting the demand and price elasticity for tittle tuna (Euthynnus affinis) in Kotabaru District, South Kalimantan Province of Indonesia. A total of 34 gillnet ship-owners were selected as the respondents to be further interviewed using questionnaire. Three independent variables i.e. price of little tuna (X1) at fishermen, price of little tuna at consumers (X2) and the price of Indian mackerel as substitute goods (X3 ) were tested to determine whether they had a significant effect on the demand for little tuna (Y). Data were input into MINITAB software and analyzed with multiple linear regressions. Data were normally distributed and free from multicollinearity and autocorrelation. The results were tested with the F-test and t-test at a confidence level of 95%. The regression equation of the model was expressed as: LnY = 29.57 + 0.524LnX1 - 0.719LnX2 - 2.175LnX3. More than 64% of variability of little tuna demand was explained by the independent variables and the rest of 36% was attributed to other variables not included in the model equation. The demand for little tuna was simultaneously significantly affected by the independent variables tested (P < 0.01). Further analysis separately showed that X1 and X2 had no significant effect on the little tuna demand (P > 0.05), while X3 in the model showed an evidence of a positive relationship (P < 0.01). The price elasticity of demand for little tuna was categorized perfectly inelastic. The changes in the prices of little tuna and Indian mackerel are complementary, and the preference is independently selected by the consumers.

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Gillnet selectivity estimates for five commercially important fish species in Tono Reservoir, Northern Ghana

Cited by 7 publications

References 12 publications

Assessing the exploitation status of main fisheries resources in Ghana’s reservoirs based on reconstructed catches and a length-based bootstrapping stock assessment method

Assessing the exploitation status of main fisheries resources in Ghana’s reservoirs based on reconstructed catches and a length-based bootstrapping stock assessment method

Climate variability, water levels, and fish catch in the Upper East Region of Ghana

Factors Affecting the Demand and Price Elasticity for Little Tuna in Kotabaru District, South Kalimantan, Indonesia

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