Growth of Octopus maya (Mollusca: Cephalopoda) of the Yucatan coast, Mexico: a long-term analysis]

Growth of the octopus (Octopus maya) off Yucatan (Mexico) was estimated from a long-term study (seven years) by the length-based methods ELEFAN, PROJMAT and SLCA. Some 19,251 octopuses with a range of mantle length between 50 and 240 mm were sampled from commercial landings in 1983-1987, 1989 and 1992. The jackknife technique was applied to deal with uncertainty in growth estimates resulting from chance variations in sampling design. The growth index phi' was used for comparative purposes. Results differed markedly among methods: ELEFAN produced parameter estimates within the range reported in the literature, whereas PROJMAT and SLCA showed problems to converge in an optimum combination of parameters, and tended to underestimate them. Jackknife analysis revealed very low intraannual variability in phi' but high variability among years, especially when applying PROJMAT. No significant differences were found in precision parameters--percent error and coefficient of variation--among methods. Estimates of phi' derived by ELEFAN varied between 4.19 and 5.23 and agreed with those reported in the literature (between 4.25 and 4.91), whereas PROJMAT and SLCA estimates were significantly lower. We suggest the use of ELEFAN, together with jackknife, to estimate growth parameters of Octopus maya.     

Determination of the unknown age at first capture of western rock lobsters (Panulirus cygnus) by random effects model

We propose a method for fitting growth curves to multiple recapture data of lobsters when the age at first capture is unknown. The von Bertalanffy growth curve is used to model the growth. To account for individual variability, the unknown age in logarithmic scale of a lobster at first capture, the individual asymptotic size, and the individual growth coefficient of its carapace length are modeled as random effects with a trivariate normal distribution. Unlike previously suggested models, the present model permits correlation between the growth coefficient and the age at first capture and can be fitted readily using existing software. The error structures between consecutive recaptures of a lobster are assumed to be a first-order autoregressive process with unequally spaced time points. A comparison between this model and the Fabens growth equation is given. The proposed method is a flexible method and can be applied to fit different growth equations when the age at first capture is unknown.     

Vital population statistics based on length frequency analysis of the exploited Japanese eel (Anguilla japonica) stock in the Kao‐Ping River,southern Taiwan

Vital statistics such as growth, mortality, and maturity parameters are crucial in understanding the population dynamics of a species. A total of 7 074 Japanese eels (Anguilla japonica) in the lower reach of the Kao‐Ping River, southern Taiwan, were collected with eel tubes in 1998 ～ 2004 and shrimp nets in 2004 ～ 2007. Data from 2004 were excluded due to mixed gear information and escapement of cultured eels; in subsequent years escaped cultured eels were identified and excluded from analyses. The estimated asymptotic length in the von Bertalanffy growth function (84.5–110 cm) was smaller, while the Brody growth parameter (0.30–0.44 year^?1) was higher using electronic length frequency analysis (ELEFAN) than when using Shepherd’s length composition analysis (SLCA). The total instantaneous mortality rate (Z) was around 1 for periods 1998–2003 and 2 year^?1 for 2005–2007 using length‐converted catch curves. The 95% confidence intervals of Z did not overlap for two of the periods, suggesting that the mortality rates were significantly higher during 2005–2007, possibly due to the introduction of shrimp nets. The maturity function differed significantly between sexes, indicating that females become silver eels at a larger size. The Japanese eels in the lower reach of the Kao‐Ping River were likely heavily exploited, thus management and conservation actions are strongly recommended.     

南海北部深水金线鱼生物学及最适开捕体长

根据1964～1965年及199～1999年在南海北部采集的深水金线鱼生物学资料,对该鱼种群体结构、资源密度分布及其季节变化、生长和死亡参数及摄食习性进行了研究.结果表明,深水金线鱼的渔获样品体长范围为4.2～21.5 cm,体重范围为2.9～241 g,分别以9.6～14.0 cm和27～59 g占优势.资源密度以春季最高、夏季最低,分别为9.92 kg·km^-2和5.53 kg·km^-2.分布的区域性变化明显,在水深60～150 m之间,深水金线鱼的渔获量随水深的增加而增大.深水金线鱼的食物以长尾类、鱼类和头足类为主.应用FiSATⅡ软件的ELEFANⅠ技术拟合的von Bertalanffy生长方程参数分别为L_∞＝22.39 cm、k＝0.44 a^-1及t₀＝-0.63 a;用Pauly经验公式计算的自然死亡系数为M＝0.94;以长度变换渔获曲线法估算的总死亡系数为Z＝2.65.运用Beverton-Holt模型分析的结果表明,该群体的最适捕捞死亡系数为F＝2.9,最适开捕年龄和体长分别为1.1 a和12.0 cm.目前该群体已处捕捞过度状态,以捕捞幼鱼问题较为突出.建议南海北部深水金线鱼的最小可捕规格为体长12.0 cm.     

Long‐term patterns in growth of Oneida Lake walleye: a multivariate and stage‐explicit approach for applying the von Bertalanffy growth function

Total length ( L _T) and its inter annual variation of walleye Sander vitreus from Oneida Lake, New York, based on 51 years (1950–2000) of data for ages 1 to 7 years were analysed. Growth increased over time at young ages, did not change at intermediate ages and decreased at old ages. Total length at age increased over time to age 4 or 5 years, but was stable at older ages. Principle component analysis was used to study the pattern of variations in annual L _T increments among years. More than 92 and 91% of inter annual variability in growth was described by the first three principal components for males and females, respectively. The first principal component was a general indicator of annual growth at all ages, but was dominated by annual growth at intermediate ages. The second and third principal components represented contrasts among yearling L _T, yearling growth and growth at older ages. Therefore, changes in the three stage‐specific parameters, yearling L _T, yearling growth and asymptotic L _T, explained most of the variance in observed growth. Using these three stage‐specific parameters for the von Bertalanffy growth function facilitated interpretations of growth comparisons.     

A skeletochronological study of age, growth and longevity in a population of the frog Rana ridibunda from southern Europe

Age at sexual maturity and longevity in a population of Rana ridibunda from north-eastern Greece were studied by skeletochronology performed on the phalanges. Analysis of the age structure was based on counting the lines of arrested growth (LAGs). Sexual maturity for both sexes arises during the first year or after the first hibernation. Ages ranged from 1 to 5 years (mean=2.96) among 52 males and from 1 to 5 years (mean=3.73) among 56 females. The mean snout-vent length was 69.03+/-12.6mm in males and 82.38+/-13.27 mm in females. The difference between the sexes in age and size was significant. Growth of individuals was fitted on? The von Bertalanffy model. The growth coefficient (K) was 0.57 in males and 0.54 in females, mainly due to faster male growth between metamorphosis and maturation.     

The life histories of endangered hammerhead sharks (Carcharhiniformes, Sphyrnidae) from the east coast of Australia

The life histories of two globally endangered hammerhead sharks, Sphyrna lewini and Sphyrna mokarran, were examined using samples collected from a range of commercial fisheries operating along the east coast of Australia. The catch of S. lewini was heavily biased towards males, and there were significant differences in von Bertalanffy growth parameters (L(∞) and k) and maturity [stretched total length (L(ST)) and age (A) at which 50% are mature, L(ST50) and A(50)] between those caught in the tropics (L(∞) = 2119 mm, k = 0·163, L(ST50) = 1471 mm, A(50) = 5·7 years) and those caught in temperate waters (L(∞) = 3199 mm, k = 0·093, L(ST50) = 2043 mm, A(50) = 8·9 years). The best-fit estimates for a three-parameter von Bertalanffy growth curve fit to both sexes were L(∞) = 3312 mm, L(0) = 584 mm and k = 0·076. Males attained a maximum age of 21 years and grew to at least 2898 mm L(ST). The longevity, maximum length and maturity of females could not be estimated as mature animals could not be sourced from any fishery. Length at birth inferred from neonates with open umbilical scars was 465-563 mm L(ST). There was no significant difference in length and age at maturity of male and female S. mokarran, which reached 50% maturity at 2279 mm L(ST) and 8·3 years. Sphyrna mokarran grew at a similar rate to S. lewini and the best-fit estimates for a two-parameter von Bertalanffy equation fit to length-at-age data for sexes combined with an assumed mean length-at-birth of 700 mm were L(∞) = 4027 mm and k = 0·079. Females attained a maximum age of 39·1 years and grew to at least 4391 mm L(ST). The oldest male S. mokarran was 31·7 years old and 3691 mm L(ST). Validation of annual growth-band deposition in S. mokarran was achieved through a mark, tag and recapture study.     

Growth patterns of Mytilopsis leucophaeata, an invasive biofouling bivalve in Europe

For the first time, growth of Mytilopsis leucophaeata, an important European fouling species, was investigated. By means of growth cages, individual shell growth of three cohorts, with, respectively, initial shell lengths of < or =5 mm, 10 mm and 15 mm, was monitored in the harbour of Antwerp, Belgium, during 2003 - 2004. M. leucophaeata followed an oscillatory growth pattern with a single summer growing period per year (May to August). Growth decreased during wintertime, but never ceased completely. M. leucophaeata has an average growth rate of < 3-6 mm year- 1. Temperature was found to be the main environmental factor affecting growth. The von Bertalanffy growth function was used to model growth of individuals < or =5 mm, resulting in Linfinity = 16.7 mm and K= 0.56. Based on a combination of growth of all three cohorts, the hypothetical growth of an average individual mussel could be modelled over a 5-year period, resulting in a maximum length > 19 mm with a growth rate of 0.41. Its longevity (more than 5 years) and the positive effect of higher water temperatures on growth, combined with its high resistance to chlorination, provides M. leucophaeata with a high potential for severe and long-lasting biofouling     

南渡江上游海南半鲿生物学参数估算

为研究海南半鲿(Hemibagrus hainanensis Tchang 1935)种群生物学及资源动态特征, 2019年1—12月于南渡江上游采集358尾海南半鲿,其体长范围为42—289 mm,体质量范围为1.14—282.79 g。利用FiSATⅡ软件中ELEFAN I法估算南渡江上游海南半鲿种群参数,其资源变动趋势则通过Beverton-Holt动态综合模型进行评估。结果显示:von Bertalanffy生长方程所描述的各参数值分别为L∞=304.5 mm、K=0.49、t0=–0.29,体质量的生长拐点为t=1.95,即TL=202.9 mm。利用Pauly经验公式和长度变换渔获曲线法分别估算出:自然死亡系数(M)为1.05,总死亡系数(Z)为1.22,捕捞死亡系数(F)为0.17及资源开发率(E)为0.14,表明其资源未处在过度捕捞状态。研究结果填补了南渡江上游海南半鲿的种群生长特性及动态特征基础资料的空白,为其种群资源恢复和保护策略的制定提供理论依据。     

Population ecology of the paddy field-dwelling fish Channa gachua (Günther) (Perciformes, Channidae) in Sri Lanka

A population of Channa gachua in a small irrigation canal that supplies rice fields was studied by monthly sampling over 2 years. The population density was positively correlated with the rainfall and varied from 0.34 to 0.95 individuals m⁻². The growth parameters of the von Bertalanffy growth equation determined on monthly size–frequency data were L_x = 179 mm total length and K =0.50. Overall male to female ratio was 0.82 and there were more females than males in the middle size classes. Spawning occurred throughout the year, but all evidence indicated enhanced breeding during major rainy periods of May to July and October to December. The length at first spawning was 102 mm, which is reached in about 20 months. Fecundity, which varied between 389 and 2130, was positively correlated with gonad weight, body weight and total length. Longevity and natural mortality were estimated as 6 years and l.27 yr⁻¹, respectively. However, 99% of the population appeared to live for only 3 years. The mean biomass, average annual production and turnover ratio of the population were 7.35 g m⁻², 12.06 g m⁻² and 1.64, respectively.     

The use of sectioned otoliths to age barramundi (Lates calcarifer) (Bloch, 1790) [Centropomidae]

The relationship between the number of rings present in sagittal otoliths and the age of barramundi, Lates calcarifer (Bloch, 1790) [Centropomidae], was investigated by examining cross sectioned otoliths of 37 tagged fish of known age between 1 and 5 years from the Johnstone River, north Queensland. Concentric rings were clearly visible in all otolith sections and were validated as annual marks. The technique was then used to estimate the age and calculate von Bertalanffy growth parameters for 70 barramundi from the Fitzroy River, central Queensland. Growth appeared to be rapid but variable in the first year; the von Bertalanffy growth parameters for length versus age were L =690 mm, K=0.53, t ₀= 0.003 years. October 1 was designated as the birth date. Whole otolith length, width and thickness were also approximated well by the von Bertalanffy equation. We suggest that examination of otoliths is a useful technique for ageing barramundi but note that further validation of the ageing method is still needed for fish older than six years.     

A seminal study of the dynamics of a mudskipper (Periophthalmus papilio) population in the Cross River,Nigeria

A seminal study was conducted in which the population dynamics (growth, mortality and recruitment) of the mudskipper (Periophthalmus papilio) in the Cross River, Nigeria, was elucidated for the first time using length frequency data and the ELEFAN software. The allometric relationship was: Weight=0.012(Length)^2.940, n=415, r²=0.939, P <0.0005. The seasonalized Von Bertalanffy growth parameters were L=19.39 cm, K=0.51 y^–1, C=0.3, and WP=0.4. The instantaneous total mortality coefficient Z was 2.208 y^–1 while the instantaneous natural mortality coefficient was 1.341 y^–1. The instantaneous fishing mortality coefficient of 0.867 y^–1 yielded the expectedly low exploitation rate E of 0.393. Our estimate shows that the species could reach an average maximum life span of about 6 years in the Cross River system. These results are used in quantitative elucidation of the state of exploitation of the population and will serve as input for the proper and scientific management of the fish resource.Alfred Wegener Institute Contribution nr. 1090.     

尖头塘鳢(Eleotris oxycephala Temmiuck et Schlegel)的年龄、生长和生活史类型的研究

本文采用胸鳍第二支鳍骨为研究东江尖头塘鳢的年龄鉴定材料。胸鳍第二支鳍骨(远侧部)长的骨(R)与体长(L)的关系L=10.6565 54.3848R。用von Bertalanffy生长方程可表达体长、体重与年龄的关系:L=298.6(1-e~(-0.2313(t 0.3028))];W_t=577.4(1-e~(-0.2313(t 0.3028))]~3。根据r-选择和K-选择的典型特征以及渐近体长(L_∞)、渐近体重(W_∞)、生长系数(K)、瞬时自然死亡率(M)、初次生殖年龄(T_m)、最大年龄(T_(max))和性腺指数(GI)等7个生态学参数值,可以判断尖头塘鳢偏向r-选择。应用平衡产量模式计算改变瞬时捕捞死亡率(F)和渔业补充年龄(t_c)时的产量变化,同样证实尖头塘鳢生活史偏向r-选择。作为渔业管理对策,尖头塘鳢的捕捞年龄可定为2—3龄,以2龄为主,这样既能保护资源,又能获得较好的经济效益。     

南海北部白姑鱼生长和死亡参数的估算

将南海北部白姑鱼分成南海北部大陆架和北部湾两个不同海域群体,根据20世纪60年代和90年代在南海北部底拖网渔业资源调查资料,利用ELEFAN技术估算了南海北部白姑鱼的生长和死亡参数.结果表明,北部湾和陆架区的生长参数L_∞、K、t₀分别为382mm、0.42、-0.16龄和315mm、0.35、-0.23龄.体重生长拐点年龄t_r分别为244和287龄;瞬时总死亡率(Z)、自然死亡率(MF)分别为3.55、0.93、2.62和3.12、0.85、2.27;当前开发率为074和073,资源处于过度利用状态.根据BevertonHolt动态综合模型,建议北部湾和陆架区白姑鱼的最适开捕年龄应大于190和195龄,相应的开捕体长大于2.11和168mm.     

Biology of the annular seabream, Diplodus annularis (Sparidae), in coastal waters of the Canary Islands

The biology of the Canary Islands annular seabream Diplodus annularis (Linnaeus 1758) was studied from samples collected between January and December 1998. Fish ranged from 82 to 209 mm total length in size and from 8.7 to 137.1 g in weight. The mean length showed an increase with increasing water depth. Males showed a negative allometric growth and females isometric growth. The species was characterized by protandric hermaphroditism. The overall sex ratio was unbalanced in favour of males (1 : 0.79). The reproductive season extended from January to May, with a peak in spawning activity in March–April. Males reached maturity at a smaller length (103 mm, 1-year-old) than females (128 mm, 2-year-old). Fish aged 0–6 years were found. The von Bertalanffy growth parameters for all individuals were: L_∞=247.9 mm, k=0.268 years^–1, and t₀=–0.879 years.     

Life history of the freshwater mussel Unio tumidiformis (Bivalvia: Unionidae) in a temporary Mediterranean‐type stream

Mediterranean‐type streams are characterized by great seasonal and annual variation in flow. We studied the biology of the freshwater mussel Unio tumidiformis in such a stream, the Vascão River in southern Portugal, during a period of great interannual variation in hydrology. We studied growth patterns of the mussels between 2002–2008, and the reproductive cycle between 2005–2006. Life‐history parameters were calculated and related to environmental variables and fish community patterns. Mark–recapture growth data confirmed that observed annuli were formed annually and are therefore reliable for use in growth studies of U. tumidiformis. The von Bertalanffy growth constant K and the asymptotic length L_∞ were negatively correlated. K varied between 0.20 and 0.58 and was positively correlated with factors related to eutrophication. The maximum observed age was 7 years, and the maximum observed length was 52 mm. There was no apparent sexual dimorphism, and sexual maturity was reached at the age of 2 years. Fecundity was low, between 1500–15000 glochidia per female, and positively correlated with body length. Only one annual gametogenic cycle was identified, leading to a short‐term reproductive period in spring (tachyticity). The reproductive cycle was similar in the two years sampled, between which hydrology and water quality differed greatly. The presence of glochidia was synchronized with the period when the proportion of fish hosts (genus Squalius) was higher in the fish community. Unio tumidiformis seems to be well adapted to the natural variability in flow in temporary Mediterranean‐type streams. Modifications of the natural flow regime caused by climate change or increased water exploitation may lead to rapid declines in mussel populations.     

Age and growth parameters of Siganus sutor in Kenyan marine inshore water, derived from numbers of otolith microbands and fish lengths

Siganus sutor (Valenciennes, 1835) is, together with the Lethrinidae, commercially the most important fish of Kenyan waters. Age and growth parameters of this fish have been estimated for stock assessment purposes, using the von Bertalanffy growth model while taking into account the initial small but finite length of fish, L _o. Microbands on the otoliths were used as a measure of age in days. Data of fish length against numbers of microbands were fitted to the growth formula by a least squares procedure applied to a non-linear fit. This gave an L _∞ of 36.2 cm s.l. and a K of 0.87 on an annual basis. Independently, a curve was fitted by eye to the same data, and values were read off the curve and used in a standard Ford–Walford plot. This gave an L_x of 35 cm and a K of 0.9. The close agreement of the values obtained by the two methods, and of these with values in the literature, demonstrates the value of using microbands for determining growth parameters in a tropical fish.     

On the dynamics of the stocks of blue mussels (Mytilus edulis L.) in the Danish Wadden Sea

As biological basis for the monitoring programme for the commercially exploited stock(s) of mussels (Mytilus edulis L.) in the Danish Wadden Sea, samples of mussels have been collected regularly since 1986, both from sub-tidal and inter-tidal mussel beds. These samples are the basis for the estimation of total biomass. They also provide data on size frequency distributions, which have been analysed for cohort identification resulting in length at age data, which again have been used for estimating parameters (L and K) for the von Bertalanffy growth equation (VBGE) as well as mortality parameters. By applying these in the Beverton & Holt model, estimates of average biomass and annual production (P) of the mussels have been obtained together with possible fisheries yields from the beds. The growth and mortality parameters and the figures for annual production and P/B are compared with figures from other investigations. These analyses have been the basis for annual assessments of the mussel stocks, which again are used in the current management of mussel fishery in the Danish Wadden Sea.     

Size frequency distribution and growth of the crabs Callinectes arcuatus and C. bellicosus (Decapoda: Portunidae) in Las Guásimas coastal lagoon, Mexico

Information on size frequency distribution, the width-weight relation and growth parameters of the crabs Callinectes arcuatus and C. bellicosus is presented. The data comes from samples taken with a trawl net both day and night on a monthly basis from March 1998 to February 2000 in a coastal lagoon from Gulf of California. C. bellicosus (n=878) was more abundant than C. arcuatus (n=357) and its size frequency distribution presented carapace width CW ranges of 8.4-166 mm and 9-130 mm respectively. Both populations were mainly represented by juveniles (75 mm in CW) ranging from 37 to 75 mm in CW, and adults (>75 mm in CW) between 76 and 90 mm in CW. In both species the width-weight relation showed that males grow more than females, with an isometric growth tendency being observed. The growth parameters for C. arcuatus estimated using the von Bertalanffy Model, were: K = 0.84 year(-1), L infinity = 140 mm to = -0.12 for C. arcuatus, and K= 0.9 year(-1), L infinity = 169 mm to = -0.11 for C. bellicosus. These results showed that the relative age at which maximum growth is attained is between three and four years for both species.     

Growth rates of juvenile smalltooth sawfish Pristis pectinata Latham in the western Atlantic

The growth rates of juvenile smalltooth sawfish Pristis pectinata collected in Florida waters between 1999 and 2006 were investigated using length-frequency and tag-recapture data. Stretched total length ( L _ST) data from 144 smalltooth sawfish (690–4960 mm) and 28 recaptures (775–2150 mm) were used for the analyses. Both methods indicated that growth was rapid during the first 2 years after birth. The L _ST increased by 650–850 mm in the first year, and by 480–680 mm in the second year. Data for animals >2200 mm were limited, so growth beyond 2 years of age was uncertain. The von Bertalanffy growth parameters estimated from L _ST frequency data were L _∞= 6000 mm, K = 0·140 year⁻¹ and t ₀=−0·863 years. Growth rates over the size range for which tag-recapture data were available were similar to that from L _ST frequency data. The growth rates reported are substantially faster than those previously assumed for this species and may have important implications for the recovery of this endangered species. There are conflicting data regarding the growth rates of older P. pectinata which need to be resolved with more data from the wild population before a complete understanding of the conservation implications can be obtained.