Fishing trend and fisheries potential analyses for the Persian Gulf and Sea of Oman, 1973-2003

Catch data from Persian Gulf and Sea of Oman during 1973 to 2001 were used to assess the state of the fishery development in these ecosystems. Also, fishery trends were analyzed to determine catch fluctuations during the period. Catch trend for each species from 1997 to 2003 was analyzed and fishing potential of the species for the following year was predicted. Based on the assessments, we can summarize fishing development in the southern waters of Iran into three periods: undeveloped, rapid development stage and developed stage. The undeveloped stage continued till early 1981, continued by a rapid stage until 1997, reaching to maximum level of at this year and continuing ever since. Catch trend analyses for each species during 1997 to 2003 showed different patterns for each species depending on its economic value. However, the mean catch of all species showed a sustainable trend in the two marine ecosystems. It is concluded that the catch quantity for most of the species have already reached a maximum level. Therefore, in order to keep fisheries sustainable in the region, excess fishing should be avoided

Estimation of growth parameters and mortality rates of kingfish (Scomberomorus commerson) in the north of Persian Gulf (Khuzestan Province)

Length composition data from monthly catches of Scomberomorus commerson landed in Choebdeh and Hendijan fish landing places in Khuzestan Province, north Persian Gulf, were collected from 2004 to 2005. We used the data to estimate growth parameters and mortality coefficients of the fish. Response surface analysis produced by the ELEFAN program provided a complete set of Von Bertalanffy growth parameters estimation. We found L infinity =120cm (fork length), K=0.49per year and t_0=-0.11 year for the fish. The length-weight relationship was estimated as W=0.022tL ^2.7575 with r^2=0.978S. Based on the calculated b, we conclude that the fish has an isometric growth pattern. The total, natural and fishing mortality coefficients were estimated as, Z=1.58, M=0.58 and F=1.0, respectively. Exploitation ratio (E) for this species was estimated as 0.63 per year. The E-value indicates that the kingfish in this part of the Persian Gulf has been overexploited. Current fishing pattern in the Khuzestan province shows that 97.07% of the cumulative length frequency and 78.18% of the cumulative weight frequency of the landed fish are under standard size. Results of this study indicate that exploitation of kingfish does not follow an optimum trend and if this trend continues, the stock of Scomberomorus commerson in this area will be threatened

Population biology and assessment of Kawakawa (Euthynnus affinis) in coastal waters of the Persian Gulf and Sea of Oman (Hormozgan Province)

Length composition data (fork length) of kawakawa (Euthynnus affinis ), landed between April 2003 to March 2005 in Coastal Waters of Hormozgan province in Iran ( Persian Gulf and Sea of Oman) , were monthly used to estimate the p opulation parameters and for the assessment of the stock. The growth parameters of von Bertalanffy equation were estimated as L∞: 87.66 cm, K: 0.51 per year and t0: -0.23 year. The estimated value of total mortality, natural mortality and fishing mortality were Z: 2.37, M: 0.65, F: 1.72 per year, respectively. Exploitation ratio (E) and Exploitation rate (U) were estimated as 0.72 and 0.65. The Annual total stock at beginning of year was calculated to be 7924 t and Annual average standing stock (S) was equal to 2994 t. By using analyses knife-edge selection method, biological reference points for kawakawa stock was calculated as, Y'/R (relative yield per recruitment) =0.062, B'/R (relative biomass per recruitment) =0.13, F max (Fishing mortality at maximum sustainable yield) =1.6, E max (Exploitation ratio at maximum sustainable yield) = 0.68 Fopt (Precautionary average target ) =0.33 year-1 and Flimit=0.43 year-1. As the exploitation ratio of kawakawa stock in this study was calculated to be over 0.5, it strongly recommended minimizing the fishing activity in this area

An estimation of growth parameter, mortality rates and yield-per-recruit for beluga (Huso huso) living in Caspian Sea

This paper presents the results of study on age, growth, mortality rates and yield-per-recruit of Beluga (Huso huso) living in Caspian Sea. The mean length of successive years, mortality rates and yield-per-recruit studies indicated that at present the resource is under heavy fishing pressure. For the female Beluga growth was regarded as comprising of three stages, and the von Bertalanffy parameters were calculated for juveniles, for middle stanza (24 years). The value of K was the highest (0.065) for the first stanza, lower for the middle (0.029) and the lowest for the third one (0.023). Total mortality of female and male Beluga estimated from the descending limb of the catch curve using the combined data (1990-1994) were: for females, Z=0.48 per year, r=0.982, p<0.01 and for males, Z=0.38 per year, r=0.992, p<0.01. Natural mortality for female and male Beluga was estimated using Richter and Efanovs formula as 0.03 for females and 0.05 for males. Values of fishing mortality (F) were estimated from Z and M, using values of Z from catch curves and M estimated from Richter and Efanovs formula as 0.045 and 0.33 for female and male, respectively. Yield-per-recruit curve was produced for female and male Beluga. It was found that the maximum Y/R (Maximum sustainable yield-per-recruit) were produced at Fs =0.07, for female and Fs=0.16 for male. Inspection of the yield-per-recruit model for the Beluga in the Caspian Sea showed that the fishing mortality should be stopped for this species in the Caspian Sea. This result confirms the over-fishing of the sturgeon in Caspian Sea. Several other authors such as Smith (1990), Birstein (1993), Bemis and Findeis (1994), Dumount (1995) and current catch data, have confirmed the overfishing of the Beluga in the Caspian Sea

Estimating growth parameters for Otolithes ruber in waters of Bushehr, Hormozgan and Sistan and Baluchestan Province, Southern Iran

Using length frequency of the Otolithes ruber collected in waters of three southern province of Iran, we estimated the fish growth parameters and monthly measured fork length of around 1000 fish caught using gill net with a mesh size of 6.5 centimeters in waters of this study area. The length infinity (L∞) in Bushehr, Hormozgan and Sistan and Baluchistan province was estimated as 58.5, 56, 59.5 centimeters, growth coefficient per year (K) as 0.48, 043, 0.32 and age at zero length (to) as -0.006, -0.002, -0.001 respectively. The relationship between length and weight of the fish in the three provinces determined. The parameters q, b and r (correlation coefficient) were 0.173, 2.868, 0.984 for Bushehr, 0.012, 2.962, 0.932 for Hormozgan and 0.056, 2.604, 0.921 for Sistan and Baluchestan province. We also evaluated the average length for the fish caught in different months and landing places. An ANOVA test showed a significant difference (P≤0.05) between the average lengths of the fish caught in different months

Age, growth and length at first maturity of Otolithes ruber in the northwestern part of the Persian Gulf, based on age estimation using otolith

Estimates of age, growth parameters, length-weight relationship and length and age at first maturity of the otolithes ruber are required for fishery management. We used counting annuli on the section of sagittal otoliths to age O.ruber from the Northwest Persian Gulf in south of Iran. Estimated ages ranged from 0 to 6 years, and maximum frequency of fishes was observed in age-group 1. The values of growth parameters L∞, k and to were calculated by von Bertalanffy model and the results were 67.57 (cm), 0.27 (year-1) and -0.43 respectively. Parameters b and an in length-weight relationship were calculated 3.19 and 0.005 respectively. Length and age at first maturity were estimated 28 cm and 1.55 year

Estimation of growth parameters and mortality rate of common carp (Cyprinus carpio, Linnaeus 1758) population in the southern Caspian Sea

Common carp (Cyprinus carpio) represents one of the most economically important fish species in the Caspian Sea. In this study, growth and mortality parameters among population of common carp was investigated. Sampling was carried out weekly, using beach seine in the south of the Caspian Sea from October 2006 to September 2007. As a contribution to elaborating management programs for common carp, the age and growth of this species was calculated via scale, growth parameters and mortality rate by length frequency data obtained from commercial fishing and research beach seines. Ten age groups were recorded from 1+ to 10+ years old, being dominated by 4 and 5 year-old fish. The growth parameters based on scale reading data by length at age analysis were FL∞= 71.52cm and K = 0.16 per year for total population, FL∞= 70.54cm and K = 0.15 per year for males, and FL∞= 72.00 cm and K = 0.16 per year for females, whereas by length frequency analysis, these values were estimated as FL∞ equals 72.0, 69.3 and 73.0cm and K equals 0.18, 0.15 and 0.18 per year for total population, males and females, respectively. The total, natural and fishing mortality rates were 0.71, 0.29 and 0.42 per year, respectively

Validation of back-calculation methods using otoliths to determine the length of anchovy kilka (Clupeonella engrauliformis)

Age structure of the Caspian Sea anchovy kilka, Clupeonella engrauliformis, was estimated for the first time by back-calculation methods. Otolith growth and the rate of increment in anchovy kilka were examined to determine whether otoliths could be used to back calculate body sizes at various life stages. Sampling was carried out on commercial fishing vessels board along the Iranian coast in 2007. The age structure of the samples ranged from 2 to 7 years old which was dominated by the third year class (38.6%). The largest fish measured was 137.2mm fork length. The relationship between fork length (FL) and otolith radius (OR) was described by the following equation: FL=13.77+ 82.78*OR (r^2=0.92). Three proportional back-calculation methods, Fraser-Lee, Whitney & Carlander and Dahl-Lea models, were compared by using data sets of anchovy kilka otoliths, and we validated back calculation by comparing them with observed lengths. Back calculated lengths generally corresponded well with observed lengths in anchovy kilka age classes. Variance of the back calculated length data obtained from three models indicated no significant difference (P>0.05)

Growth, mortality and spawning season of the spangled emperor (Lethrinus nebulosus Forsskal, 1775) in coastal waters of Hormozgan Province in the Persian Gulf and Oman Sea

The population parameters and spawning season of the Spangled emperor (Lethrinus nebulosus) were studied in coastal waters of Hormozgan province. The monthly calculated mean values of gonadosomatic index (GSI) of females were indicate to increase from February, reach the highest in March and decline in June. The spawning season peak of L. nebulosus occurred in March. The Von Bertalanffy growth parameters, L∞, K and t0 were estimated as, 67.2cm, 0.16.year^-1 and -1.161 year, respectively. The relationship between weight and length (Fork Length) can be expressed as W=0.051 L^2.722, which indicates that Spangled Emperor has negative allometric growth. Using length converted catch curve, total mortality (Z) was estimated as 1.13 year^-1 and natural mortality was estimated using Pauly's equation, as 0.57 per year. Finally, the fishing mortality (F) was 0.56, which gives an exploitation rate (E) of 0.50

Growth parameters and mortality rates of Liza klunzingeri in the Iranian waters of the Persian Gulf and Oman Sea, using Length Frequency Data

The aim of the present study was to investigate the population dynamics of Liza klunzingeri, in Hormouzgan province waters located in northern coasts of the Persian Gulf and Oman Sea. This study was carried out from October 2007 to September 2008. Samples were collected from commercial stake traps. The relationship between weight and fork length was found to be W= 0.0214 F.L^2.8233 suggesting that Liza klunzingeri shows isometric growth. Length-based stock assessment using the FiSAT software package showed an asymptotic length (L∞) of 20.3cm FL and growth coefficient of 0.6.yr^-1. These results gave a growth performance index (ø) of 2.39. The total mortality coefficient was estimated to be 2.31, a natural mortality of 1.09 and fishing mortality of 1.22. The estimated total mortality which, in relative terms, is considered average (2.31.yr^-1), coupled with the currently observed exploitation rate of 0.52 for L. klunzingeri, estimated from the mortality rates, suggested that the species is moderately exploited