scholarly journals Population characteristics and exploitation of yellowfin tuna (Thunnus albacares Bonnaterre, 1788) in the coastal waters of Kenya

2021 ◽  
Vol 20 (1) ◽  
pp. 95-109
Author(s):  
Edward Kimakwa ◽  
Micheni Ntiba ◽  
Agnes Muthumbi
Keyword(s):  
Coastal Waters ◽  
Growth Parameters ◽  
Total Mortality ◽  
Mortality Rates ◽  
Yellowfin Tuna ◽  
Population Characteristics ◽  
Thunnus Albacares ◽  
Catch Per Unit Effort ◽  
Length Frequency ◽  
South West Indian Ocean

Yellowfin tuna, Thunnus albacares (Bonnaterre, 1788) is a highly migratory and important commercial fishery species. Data on length-frequency, growth parameters and mortality rates of yellowfin tuna in the coastal waters of Kenya is limited. We assessed Catch Per Unit Effort (CPUE), size distribution, growth parameters and mortality rates based on length-frequency and catch data collected from August 2015 to December 2016 at five fish landing sites along the Kenyan coast. The sample comprised of 1281 individuals of yellowfin tuna weighing 12,671 kg. Highest CPUE was recorded in October 2015 (10.8 kg·Fisher-1Trip-1) and lowest CPUE, 2.6 kg·Fisher-1Trip-1 in December 2016. Yellowfin tuna was more abundant in the South-East Monsoon (SEM), from May to October, with an average CPUE of 7.3 kg Fisher-1Trip-1 compared to North East Monsoon (NEM), from November to April, with a CPUE of 7.0 kg Fisher-1Trip-1. Spatial variation of CPUE was evident. Old Town recorded the highest CPUE of 54.2 kgTrip-1, while Mnarani the lowest of 19.4 kgTrip-1. At least 91 % of the fish sampled were < 100 cm FL and hence not yet mature. The asymptotic Length (L∞) was found to be 195 cm FL, the Von Bertalanffy growth constant (K) 0.43 year-1, t0 - 0.82 and the Growth Performance Index (f) 4.21. The total mortality coefficient (Z) was 2.59 year-1 , Natural Mortality (M) 0.59 year-1, Fishing Mortality (F) 2.00 year-1 and Exploitation Rate (E) 0.77 year-1. Results show that mortality and exploitation rates were above the optimal, indicating high fishing pressure on coastal yellowfin tuna. The information generated by this study provides some further insights on the scientific knowledge of the coastal yellowfin tuna to inform policy for sustainable management and development of this fishery in Kenya and the entire South West Indian Ocean (SWIO) region.

scholarly journals Assessment of the fishery, growth and mortality characteristics of the cassava croaker, Pseudotolithus senegalensis (Sciaenidae) from coastal waters of Ghana

2020 ◽  
Author(s):  
Isaac Okyere ◽  
John Blay
Keyword(s):  
Coastal Waters ◽  
West African ◽  
Population Characteristics ◽  
Western Region ◽  
Population Parameters ◽  
Catch Per Unit Effort ◽  
Length Frequency ◽  
Growth Coefficient ◽  
Fishing Season ◽  
Relationship Of

Abstract This paper reports on the fishery and some population parameters of the cassava croaker (Pseudotolithus senegalensis) at Anlo Beach near Shama (5° 01' N, 1°37' W) in the Western Region of Ghana. The study was conducted from July 2012 to June 2013 to contribute to information on the dynamics of demersal stocks in the country. Beach seining was the prime fishing method in the area with the fishing season spanning July to March. Catch per unit effort (CPUE), determined as catch per net haul per day was 9.5 kg per haul in July 2012, 110 kg per haul in January-February 2013 and 47 kg per haul in March 2013. The species was absent from the fishery from April 2013 to June 2013. Monthly catches varied from 2,295 kg to 31,500 kg, and specimens of the fish measured 7.5 cm TL to 105.4 cm TL and weighed 2.9 g to 7,634 g. The length-weight relationship of the population was described by the equation: BW = 0.005TL3.04 (r = 0.99), and grouping the fish at 5 cm class intervals showed modal lengths at 15.0 – 19.9, 35.0 – 39.9 and 60.0 – 64.9 cm TL. Analysis of the length-frequency distribution using the ELEFAN programme indicated an asymptotic length (L∞) of 110.3 cm TL, a growth coefficient (K) of 0.2 yr-1, and total (Z), natural (M) and fishing (F) mortality coefficients of 0.68yr-1, 0.42 yr-1, and 0.26 yr-1 respectively, for the population. Longevity of the fish was estimated to be 15 years. A low exploitation level of the stock is suggested by the calculated exploitation ratio, E= 0.38. These population characteristics are compared with those of other West African P. senegalensis populations.

Exploitation and movements of yellowfin tuna (Thunnus albacares) and bigeye tuna (T. obesus) tagged in the north-western Coral Sea

1998 ◽  
Vol 49 (6) ◽  
pp. 475 ◽  
Author(s):  
John Hampton ◽  
John Gunn
Keyword(s):  
Seasonal Pattern ◽  
Yellowfin Tuna ◽  
Thunnus Albacares ◽  
Bigeye Tuna ◽  
Catch Per Unit Effort ◽  
The North ◽  
Coral Sea ◽  
Release Area ◽  
Seasonal Signal ◽  
North Western

Yellowfin tuna (Thunnus albacares) and bigeye tuna (T. obesus) were tagged and released in the north-western Coral Sea off northern Queensland in 1991 and 1992. Over the next five years, recaptures were reported by Australian longline vessels based in Cairns and fishing in the release area, and by industrial tuna fleets fishing in the adjacent western Pacific region, thus demonstrating clear links between the tuna stocks in these areas. Some southerly movements of yellowfin, in particular, further suggested links with stocks supporting the longline fishery in the south-eastern Australian Fishing Zone. Bigeye tuna tag returns and catch per unit effort by Cairns-based longliners showed a strong seasonal signal, peaking in mid year. Yellowfin tag-return data displayed a similar, but weaker, seasonal pattern. The data were analysed by use of tag-attrition models with seasonally variable catchability and with two assumptions regarding changes in targeting of the two species by longliners during the study. Under both assumptions, the local exploitation rates for yellowfin are low: about 0.07 in 1996. For bigeye, the local exploitation rate in 1996 may have been as high as 0.30, warranting a cautious approach to further fishery expansion in this area.

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.  

Length-weight relationship, growth and mortality ofAnadara granosain Penang Island, Malaysia: an approach using length-frequency data sets

2014 ◽  
Vol 95 (2) ◽  
pp. 381-390 ◽  
Author(s):  
Mohammad Reza Mirzaei ◽  
Zulfigar Yasin ◽  
Aileen Tan Shau Hwai
Keyword(s):  
Growth Parameters ◽  
Total Mortality ◽  
Growth Function ◽  
Data Sets ◽  
Frequency Data ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Weight Relationship ◽  
Logarithmic Relationship ◽  
Length Frequency Data

Length-weight relationship, growth parameters and mortality rates ofAnadara granosain the intertidal zone of Balik Pulau, Penang Island, West Coast of Malaysia were investigated based on monthly length-frequency data (December 2011 to November 2012). A total of 548 individuals ranging from 11.25 to 33.13 mm size were subjected to analysis. Logarithmic relationship between the length and weight was LogW = 2.328LogL − 2.537 (R2 = 0.922) for combined sexes. From this equation it was clear that the exponent ‘b’ value forA. granosashowed a negative allometric growth (b < 3). A von Bertalanffy growth function with an asymptotic length (L∞) of 35.40 mm and a growth constant (K) of 1.1 year−1was established from length frequency distributions. Thet0(−0.140) was estimated by substituting theL∞andKin the Pauly's equation. The sizes attained byA. granosawere 10.13, 14.36, 17.89, 20.82, 23.56 and 25.29 mm at the end of 2, 4, 6, 8, 10 and 12 months, respectively. The estimated growth performance index (Ø) was 3.13 while the estimated lifespan of the cockles was about 2.72 years at the study area. The estimated value of total mortality based on length-converted catch curve wasZ = 3.02 year−1. The natural mortality (M) and fishing mortality (F) rates were 1.84 and 0.48 year−1, respectively. The exploitation level (E) ofA. granosawas 0.20, which indicated slight fishing pressure on the stock.

Hierarchical interpretation of nonlinear relationships linking yellowfin tuna (Thunnus albacares) distribution to the environment in the Atlantic Ocean

2001 ◽  
Vol 58 (3) ◽  
pp. 458-469 ◽  
Author(s):  
Olivier Maury ◽  
Didier Gascuel ◽  
Francis Marsac ◽  
Alain Fonteneau ◽  
Anne-Laure De Rosa
Keyword(s):  
Adult Population ◽  
Yellowfin Tuna ◽  
Additive Models ◽  
Small Scale ◽  
Physical Factors ◽  
Thunnus Albacares ◽  
Catch Per Unit Effort ◽  
Low Salinity ◽  
Nonlinear Relationships ◽  
Unit Effort

Using generalized additive models, we show evidence for nonlinear relationships between various hydrological factors and age-structured catch per unit effort of Atlantic yellowfin tuna (Thunnus albacares) for two fishing fleets. Catchability effects are distinguished from tuna environmental preference effects in the catch per unit effort variability. With respect to catchability, an important nonlinear effect of local fishing effort is highlighted for each fleet. It is interpreted as resulting from a local overfishing phenomenon of adult yellowfin tuna and from vessel fishing tactics (cooperation/spying). The environmental preferences obtained facilitate the interpretation of the hierarchical spatial distribution and age-dependent movements of the yellowfin population. We show that, on a large spatiotemporal scale (the whole ocean), low salinity is a good predictor of yellowfin habitat. Juveniles are mainly distributed in low-salinity waters (<0.035 kg·kg–1) when adults extend their range to waters of 0.036 kg·kg–1. On a mesoscale, adult population annual reproductive transatlantic displacements are probably driven by temperature and salinity gradients to warm and low-salinity locations that are favorable for juveniles. North–south seasonal movements of the population are clearly related to warmwater seasonal oscillations. On a small scale, ocean thermic stability and gradients of sea surface temperature are important physical factors determining yellowfin concentration.

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.

scholarly journals Ocean variations associated with fishing conditions for yellowfin tuna (Thunnus albacares) in the equatorial Atlantic Ocean

2011 ◽  
Vol 68 (6) ◽  
pp. 1063-1071 ◽  
Author(s):  
Kuo-Wei Lan ◽  
Ming-An Lee ◽  
Hsueh-Jung Lu ◽  
Wei-Juan Shieh ◽  
Wei-Kuan Lin ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Net Primary Productivity ◽  
Principal Component ◽  
Yellowfin Tuna ◽  
Subsurface Water ◽  
Thunnus Albacares ◽  
Equatorial Atlantic ◽  
Catch Per Unit Effort ◽  
The North ◽  
Equatorial Atlantic Ocean

Abstract Lan, K-W., Lee, M-A., Lu, H-J., Shieh, W-J., Lin, W-K., and Kao, S-C. 2011. Ocean variations associated with fishing conditions for yellowfin tuna (Thunnus albacares) in the equatorial Atlantic Ocean. – ICES Journal of Marine Science, 68: 1063–1071. In this study, the Taiwanese longline (LL) fishery data were divided into two types: regular LL and deep LL. Furthermore, we collected environmental variables, such as sea surface temperature (SST), subsurface temperature, chlorophyll a concentration, net primary productivity, windspeed, and the north tropical Atlantic SST index (NTA) during the period 1998–2007 to investigate the relationship between LL catch data and oceanic environmental factors using principal component analysis (PCA). After the daily LL was separated into two types of LL, the results indicated that the deep LL was the major fishery catching yellowfin tuna (YFT) in the equatorial Atlantic Ocean. In 2003–2005, especially in 2005, the monthly catch by deep LL was double those of other years. The spatial distribution of the nominal catch per unit effort (cpue) by deep LL showed the maximum aggregation of YFT in waters with temperature above 24–25°C. The YFT mainly aggregated in the equatorial Atlantic, extending east in the first and second quarters of the year. In the third quarter of the year, the SST decreased off West Africa and the YFT migrated westwards to 15°W. Results of PCA indicated that higher subsurface water temperatures resulted in a deeper thermocline and caused a higher cpue of YFT, but the influence of NTA on the cpue of YFT seemed to be insignificant.

scholarly journals Application of Surplus Production Model to the Yellowfin Tuna Thunnus albacares in the northern and western parts of Aceh waters

2021 ◽  
Vol 869 (1) ◽  
pp. 012072
Author(s):  
A Rahmah ◽  
I Mardhatillah ◽  
A Damora ◽  
M Muhammad ◽  
N Nurfadillah
Keyword(s):  
Economic Value ◽  
Maximum Sustainable Yield ◽  
Yellowfin Tuna ◽  
Production Model ◽  
Purse Seine ◽  
Thunnus Albacares ◽  
Catch Per Unit Effort ◽  
Surplus Production ◽  
Surplus Production Model ◽  
Banda Aceh

Abstract Yellowfin tuna Thunnus albacares is one of pelagic fish that has high potential and economic value in Banda Aceh. Utilization of this resource in Banda Aceh is using purse seine units, with the number of purse seines continuously increasing. Therefore, management needs to be done so that optimal productivity can be maintained. This study discusses the estimation of catch and effort at maximum sustainable yield (MSY) of yellowfin tuna based on catch per unit effort (CPUE) and purse seine production in Banda Aceh during 2013-2018. Mathematical analysis was carried out using the equilibrium approach with the Schaefer model. The highest catch of yellowfin tuna reached 191 tons (July) and the average CPUE for yellowfin tuna was 0.796 tons/trip with CMSY of 2,482 tons/year and EMSY of 2,765 trips/year. From 2015 to 2018, the trend of biomass continued to decline and overfishing occurred during this period.

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