Length-weight relationships for six freshwater fish species in Iran

The aim of this study is to report the length-weight relationship parameters (a and b) for some economically important fish species from Iranian freshwaters. The length-weight relationships (LWR) are calculated for six freshwater fish species collected during 2006 and 2007 in Iran. The values of the exponent b in the LWR (W=aLb) vary between 2.985 and 3.543. The LWR with high correlation coefficient (r2) is significant for all the species. These parameters are of great importance to evaluate the relative condition of populations, biology, species management and their fisheries and stock assessment. The application of the length-weight relationships presented here should be limited to the observed length ranges.

Length-weight and Length-length Relationships for Nine Freshwater Species from Huaihongxinhe River, Huaihe River Basin, East China

The present paper provided length-weight relationship(LWR)and length-length(LLR)relationship for the nine freshwater species from Huaihongxinhe River,a tributary of Huaihe River in east China.The data was based on monthly sampling(from August 2016 to December 2016)of the nine fish species.Samples were obtained using barrier net,gill net and ground cage in Huaihongxinhe River.The log-transformed data were used to establish the standard length-body weight and standard length-total length relationships by linear regression analyses.This study would be useful for fishery management and conversation in Huaihe River Basin.

Community structure of mesopelagic fauna and the length-weight relationships of three common fishes in the Cosmonaut Sea,Southern Ocean

This study used specimens of marine organisms caught by rectangular midwater trawl in the Cosmonaut Sea,Southern Ocean,in austral summer 2019/2020,to determine species composition and spatial distributions of mesopelagic fauna in this sea.The data were also used to calculate the length-weight relationships of three common fishes captured during the survey(Electrona antarctica,Bathylagus antarcticus,and Cyclothone microdon).A total of 385 individual organisms with a total weight of 15462.2 g and representing 17 species were collected across the 11 stations visited.The small-sized crown jellyfish Atolla wyvillei(order Coronatae)was the most-dominant species by number(96 individuals),and the zooplankton Cyllopus lucasii(Amphipoda)also showed high abundance(54 individuals).Among fishes,81 individuals of Notolepis coatsorum(Paralepididae)were caught,followed by 71 individuals of E.antarctica(Myctophidae),25 individuals of B.antarcticus(Bathylagidae),and 16 individuals of C.microdon(Gonostomatidae).Clustering analysis divided the mesopelagic community into“west”and“east”groups,and a greater number of individuals were collected in the western part of the sea.The length-weight relationships of the three common fishes revealed positive allometric growth for B.antarcticus(b=3.16),and negative allometric growth for E.antarctica and C.microdon(both b=2.53).Our descriptions of the mesopelagic-zone community structure and biological features of three common fishes provide basic information on the ecology of the Cosmonaut Sea,Southern Ocean,and will be useful for ecosystem-based fisheries management in this region.

Relationships between sagittal otolith size and body size of Terapon jarbua (Teleostei, Terapontidae) in Malaysian waters

Length-weight relationship provides basic information of a fi sh’s condition while the morphometric data of otolith has been traditionally used to determine the range of fi sh sizes for various purposes.The length-weight relationship of Terapon jarbua(Forskål,1775)was examined from 165 specimens,while 132 specimens were used in sagittal otolith biometry measurements.Fish specimens were obtained from various locations in Malaysia including Pahang,Selangor,Sarawak,and Sabah.The total length of fi sh ranged 12.5–32.5 cm,while the total weight ranged 26.28–444.30 g.The otolith length ranged 0.423–1.070 cm,and the otolith weight was 0.0103–0.1572 g.The specimens displayed a mixture of positive and negative allometry growth as indicated by fl uctuating b values between 2.74 and 3.15.The overall coeffi cient of determination(R 2)between fi sh length and weight was 0.9729,which implies a strong correlation.All regressions between the fi sh length and otolith dimensions were highly signifi cant(P<0.001).The otolith dimensions found to be most closely related to the fi sh total length was the otolith weight.This was supported by the regression model showing a high R 2 value of 86.57%.The aspect ratio of otolith was 1.80±0.14(mean±SD).Results confi rm that the otolith growth refl ects the somatic growth of T.jarbua.The length-weight relationship explained the growth conditions of the fi shes in each location while the overall b value of 2.91 indicates that the condition of T.jarbua grown in Malaysian waters during the study period was generally in good condition.This study contributed to the database on the morphometric data of otolith of T.jarbua as well as the fi rst report on fi sh length-weight relationship for T.jarbua in Malaysia.

Length-weight Relationship and Condition Factor of Sarotherodon Melanotheron(Perciformes:cichlidae)from Forcados River Estuary,Niger Delta,Nigeria

Length-weight relationship(LWR),condition factor(k)of the black chin tilapia,Sarotherodon melanotheron(Rüppel,1852)from Forcados River estuary Nigeria was investigated.The fish were collected monthly from fishermen for a period of 24 months(between April 2012 and March 2014).699 specimens of the fish species were collected.The Length-weight relationship(LWR)of the fish was evaluated using the equation:W=a L^(b) while the condition factor of the fish was determined using the equation;K=100W L^(b).The standard length of sampled S.melanotheron ranged from 4.15 to 18.92 cm,total length 6.01 and 22.5 cm while the weight ranged from 7.85-286.71 g.The b value 2.1299 was less than 3 indicating that the growth pattern of the fish was allometric.The correlation co-efficient(r)value for S.melanotheron was 0.7528.The condition factor for the combined sexes fluctuated monthly.The length-weight relationships and condition factor of S.melanotheron in Forcados river estuary indicated that the fish were above average condition.

贵州北部云南光唇鱼野外和驯养种群的生长模式研究

【目的】探明贵州北部云南光唇鱼(Acrossocheilusyunnanensis)自然栖息环境和驯养条件下体长与体重的关系,分析其群体生长规律,为当地云南光唇鱼资源的保护和开发提供参考。【方法】测定野外种群和驯养种群个体的体长、体重,利用单因素方差分析、t检验、幂函数回归等方法分析有关指标。【结果】云南光唇鱼野外种群体长为80~171 mm,平均体长为(134.55±20.34)mm;驯养种群体长为150~245 mm,平均体长为(167.51±15.18)mm;平均体长驯养种群显著大于野生种群。云南光唇鱼野生种群体重为21~112 g,平均体重为(69.92±18.99)g;驯养种群体重为52.9~143.0 g,平均体重为(78.03±18.42)g;驯养种群平均体重显著大于野生种群。云南光唇鱼野外种群体长和体重均呈左偏分布,驯养种群均呈右偏分布。从变异系数看,云南光唇鱼野外种群体长和体重整齐度均低于驯养种群。云南光唇鱼体长-体重关系式野生种群为W=0.0011L^(1.9896)(n=100,R^(2)=0.9847),驯养种群为W=0.0002L^(2.2119)(n=100,R^(2)=0.7758)。野生种群与驯养种群体长与体重参数a值和b值分别为0.000005~0.009397和1.5176~2.8341。野生种群与驯养种群的参数a值呈由高到低的变化趋势,参数b值呈与a值相反的变化趋势。单因素方差分析表明,云南光唇鱼野外种群与驯养种群各阶段体长与体重关系参数a值、b值差异不显著。t检验表明,野外种群b值与3差异极显著,驯养种群b值与3差异不显著。【结论】贵州北部云南光唇鱼野外种群生长为负异速生长,人工驯养条件下为等速生长。贵州北部云南光唇鱼野生环境优于驯养试验环境,天然栖息环境和驯养环境的综合环境条件均较差。

长江靖江段沿岸凤鲚丰度的时间格局及生物学研究

为探究长江南通段以上凤鲚(Coilia mystus)的资源动态,通过在靖江段沿岸连续10年(2008—2017年)的定置张网实地监测,初步分析了该江段凤鲚丰度的时间格局;采用逐年拟合群体体长-体质量关系,绘制体长和体质量频率曲线图,分析了凤鲚生物学参数的时间变化。结果显示,在10年343次采样中,采集到凤鲚样本130次,出现率为37.9%。凤鲚在靖江段渔获物中的数量与重量占比分别仅为0.72%、0.44%,且丰度和出现率在年间均呈递减趋势。在繁殖季节共采集到721尾,占全部个体数的87.5%;在非繁殖季节采集到103尾,占全部个体数的12.5%,表明在非繁殖季节仍有少部分凤鲚个体滞留在淡水。互相关分析显示,靖江沿岸凤鲚丰度与当年长江口凤鲚繁殖期的捕捞量呈显著的正相关关系(r=0.819,P<0.05),表明长江口繁殖群体中有部分个体可继续上溯到靖江以上的上游江段。生物学研究显示,凤鲚群体平均体长和体质量分别为(105.6±1.8)mm和(5.07±0.28)g,体长-体质量关系式为:W=2.958×10-6L3.020(R2=0.9647)。与同期长江口的风鲚群体相比,靖江段群体的体长和生长参数b均很接近,但体质量和丰满度略小。

Population dynamics of Japanese threadfin bream Nemipterus japonicus from Pakistani waters

Japanese threadfin bream Nemipterus japonicus（Bloch, 1791） is among the most abundant and commercially important species in Pakistan. From the coast of Pakistan, four demersal trawl surveys in October–November 2009 and May–June, August, October and November in 2010 were carried out. The purpose of this study is to estimate the population dynamics and status of the stock of the N. japonicus from Pakistani waters based on the research trawl surveys from the research area. The data consist of n=784 length-weight pairs and n=7 530 length frequency with the maximum length and weight of 29 cm and 358 g respectively. The length frequency data were analyzed using ELEFAN method in FiSAT computer package. The parameters of length and weight relationship were b=2.778, a=0.032 and R2=0.973. The estimated von Bertalanffy growth function parameters were L∞=30.45 cm, K=0.270 year-1. Based on length-converted catch curve analysis the total mortality（Z） during this study was estimated at 0.960 year-1. The natural mortality coefficient（M） was 0.74 year-1 using Pauly＇s equation（the annual average sea surface temperature was 27°C）, therefore, the fishing mortality coefficients（F） were 0.22 year-1. The yield per recruit analysis indicated that when tc was 2, Fmax was estimated at 1.2 and F0.1 at 1.1. When tc was 1, Fmax was estimated at 0.95 and F0.1 at 0.8. Because current age at first capture is about 1 year and Fcurrent was 0.22, Fcurrent is smaller than F0.1 and Fmax, which indicated that the fishery is about in a safe condition. When using Gulland（1971） biological reference point, Fopt was equals to M（0.74）. The current fishing mortality rate of 0.22 was smaller than the target biological reference point.

Downstream Changes on a Tropical Fish Community Structure by Effluent from Wood Processing Factory

In order to plan a management programme for ensuring maximum production of fish in Cross River, impacted downstream changes in the fish community structure by effluents from wood processing industry, six years after establishment, was examined. Monthly samples were collected between January and December each year from 2000 to 2006 in three reaches (Upriver: I, Mid-river: II and Downriver: III) along the length of Cross River. Representatives of the fish families Osteoglossidae (i.e. Heterotis niloticus), Cichlidae (Tilapia melonopleura) and Characidae (Bryocinus nurse), Clupeidae (Cynothrissa sp), Mormyridae (Mormyrus deliciosus), Clariidae (Clarias gariepinus), Bagridae (Bagrus bayad) and Cyprinidae (Barbus occidentalis) were found to have declined in their importance compared to pre-industry period. On the other hand, Bagridae (Chrysichthys nigrodigitatus), Cichlidaae (Orechromis niloticus), Claridae (Clarias anguillaris) and Mochokidae (Synodontis clarias) have currently emerged as most important. Estimated value of growth coefficient (b) of the length-weight relationship changed from isometry (b approx. = 3) to negative allometry (b ≤ 3), condition factor values decreased from range between 0.53 and 1.30 to range between 0.22 and 0.62. Main feeding groups of fish;planktivores, carnivores and insectivores declined in numbers while omnivores and detritivores increased, resulting in dominance of benthic and semi-pelagic omnivores. Values of fecundity distribution varied from 56,012 ± 5234 eggs, mode 12,500 and median 58,345 to mean value 23,122 ± 232 eggs, mode 2500 and median 20,349, egg size from mean value;1.82 ± 0.07 mm, mode 2.2, and median;1.8 to values of 0.8 ± 0.04 mm, mode;1.3 and median 1.1 and Gonadosomatic index from 20.5 ± 3.2, mode 19.1 ± 2.2 and median 21.4 to values of 12.4 ± 2.3, mode 4.5 and median 9.5 respectively. Three species found to have appeared in the river were Tilapia monody, Chrysichthys maurus and Synodontis violaceus. The appearance of these species and disappearance of 36 others indicates the restructuring of the fish community of the Cross River by effluents from the wood processing industry.

Population dynamics of the tropical oyster Magallana bilineata(Mollusca,Bivalvia,Ostreidae)in Mengkabong Bay,Tuaran,Malaysia

Knowledge about the population dynamics within a specific spatial area is vital for the effective planning and management of important fishery resources.Population parameters,including the asymptotic length(L∞),growth coefficient(K),mortalities(Z,F,and M),recruitment pattern,exploitation level(E),and yield per recruit(Y’/R),of the tropical oyster Magallana bilineata in Mengkabong Bay,Tuaran,Malaysia were analyzed by using the FiSAT software,using on the monthly shell length-frequency data collected from April 2019 to March 2020.A total of 435 oysters with shell lengths ranging from 3.64 to 11.16 cm were analyzed.Habitat water temperature,salinity,dissolved oxygen,hydrogen ion concentration(pH),and chlorophyll concentration were measured at 29.0-33.7◦C,26.68-35.74 psμ,3.18-6.99 mg/L,6.57-8.29 and 1.51-98.93μg/L,respectively.The logarithmic relationship between the length and weight of Log W=1.9055 Log L+0.1049(R2=0.5431)with exponent b of 1.9055 for combined sexes showed a negative allometric growth(b<3),indicating that the oysters in Mengkabong Bay are skinny.Several management measures have been proposed to promote high meat growth,including the use of genetically selected seeds,selection of new farming sites and adoption of grow-out methods that favour high meat growth.Asymptotic length(L∞)and growth coefficient(K)of the von Bertalanffy Growth Formula(VBGF)for M.bilineata were estimated at 12.13 cm and 1.00 yr1,respectively.The theoretical ages at length zero(t0)(0.0487)were estimated by substituting L∞and K in Pauly’s equation.The sizes attained by M.bilineata were 3.76,5.04,6.13,7.05,7.83,and 8.49 cm at the end of 2,4,6,8,10,and 12 months,respectively.The calculated growth performance index(φ)for M.bilineata in Mengkabong Bay was 2.168,while the estimated lifespan was 3 years.The recruitment pattern was observed year-round,with higher recruitment activities in September-October 2019 and January 2020.The total mortality(Z)was analyzed using the length-converted catch curve and estimated at 3.04 yr^(-1),fishing mortality(F)at 0.63 yr^(-1),and natural mortality(M)at 2.41 yr^(-1).The lower exploitation rate(0.21)compared to the recommended 0.5 and Beverton and Holt’s estimated maximum allowable limit of exploitation rate(Emax)of 0.587 indicated that the M.bilineata stock in Mengkabong Bay was under-exploited.Several recommendations that could aid in the development of M.bilineata in Mengkabong Bay include promoting local oysters through collaboration with leading hotels and restaurants,developing food processing technology for downstream products,and establishing a sanitation programme that includes monitoring and enforcing sanitary conditions in the culture,harvest and processing sectors.

Some reproductive and biometric features of the endangered Gangetic Leaf Fish,Nandus nandus(Hamilton,1822):Implication to the baor fisheries management in Bangladesh

This study reflects the biometric characters of the endangered species Nandus nandus(Hamilton,1822)including sex ratio,length-length relationships(LLRs),and length-weight relationships(LWRs)utilizing the sum of 14 linear variables,various meristic measurements,reproductive biology,and condition factor from the Borni Baor,a large wetland ecosystem of southwestern Bangladesh.A total of 579 specimens of N.nandus have been periodically collected from the Borni Baor throughout the year(January-December,2019)using different traditional fishing gears.Highly significant LLRs(r^(2)>0.90)values indicate that length parameters are profoundly associated with one another.In the LWR formula(W=aL^(b)),higher exponent b values(b>3.0)were demonstrating a positive allometric growth with a high correlation coefficient(r^(2)>0.94).Moreover,monthly gonadosomatic index and dobriyal index fluctuations suggest the primary breeding season of this fish is from March to July.Data revealed the breeding time was associated strongly with the rainfall and air temperature(p<0.05).The results of our study exposed a cutting-edge biometric feature of this endangered species that would be applicable for fish stock evaluation and making management strategies and conservation policy for this valuable fish resource.

Biometrics of the rare fish Rhinomugil corsula(Hamilton,1822)(Mugiliformes:Mugilidae)in the Ganges,Northwestern Bangladesh

Objective:To investigate biometrics of the Rhinomugil corsula(Hamilton,1822)(R.corsula),including length-weight relationships(LWRS),condition factors(Allometric,K_(A);Fulton's,K_(F);Relative,K_(R);Relative weight,W_(R)),and sex ratio and length-frequency distributions in the Ganges(Padma River),Northwestern Bangladesh.Methods:Monthly sampling was conducted using traditional fishing gears during June to August 2012.Total length was measured to the nearest 0.01 cm using digital slide calipers,and total body weight was measured using an electronic balance with 0.01 g accuracy.The LWR was calculated using the expression:W=a×L_(b),where the W is the body weight,L is the total length,a and b are the parameters of the regression.Results:A total of 350 specimens ranging from 8.59-15.71 cm in total length and 9.57-32.59 g in body weight were analyzed during this study.The overall sex ratio was not significantly different from the expected value of 1:1(X^(2)=2.57,P>0.05),but there was significant difference in the length-frequency distributions between the sexes(P=0.03).The allometric coefficient b for the LWR indicated negative allometric growth(b=3.00)in males,female and combined sexes.Results further indicated that Kr was not significantly different between the sexes(P=0.57).However,the mean W_(R)of R.corsula showed significant differences from 100 for males(P=0.03)and females(P<0.001)in this study,indicating the imbalance habitat with food availability relative to the presence of predators.Conclusions:This study reported the first description of biometric relationships for R.corsula,which would be useful for the sustainable conservation of this rear fishery in Bangladesh and also neighboring countries.

Biological parameters and feeding behaviour of invasive whelk Rapana venosa Valenciennes,1846 in the south-eastern Black Sea of Turkey

Objective:To determine length-weight relationships,growth type and feeding behavior of the benthic predator Rapa whelk at the coast of Camburnu,south-eastern Black Sea.Methods:Rapa whelk was monthly collected by dredge sampling on the south-eastern Black Sea at 20 m depth.The relationships between morphometric parameters of Rapa whelk were described by linear and exponential models.The allometric growth of each variable relative to shell length(SL)was calculated from the function Y=aSL^(b) or logY=loga_(+)blogSL.The functional regression b values were tested by t-test at the 0.05 significance level if it was significantly different from isometric growth.The total time spent on feeding either on mussel tissue or live mussels was recorded for each individual under controlled conditions in laboratory.Results:The length-weight relationships showed positive allometric growth and no inter-sex variability.Body size in the male population was significantly higher than in the individuals of the female.All characters in males and females showed a trend towards allometry rather than isometry.While the total time spent feeding increased with increasing prey size the total time that Rapana venosa spent feeding decreased with increasing Rapa whelk size.The total average feeding time needed by Rapa whelks was 160 min.But they took 310 min on live mussels in 27-28℃ in the laboratory conditions.Conclusions:Length and weight relationships,growth type,total time spent feeding of this species were explained in details for this region.It would be useful to sustainable management in the south-eastern Black Sea of Turkey.The results about the feeding behaviour of this species will contribute to the understanding of the role of this species within the ecosystem.