Parameters Of Von Bertalanffy Growth Equation Research Articles

Life History of Mediterranean Horse Mackerel Trachurus mediterraneus (Carangidae) from Crimea (Black Sea)

The sex ratio, body length–age structure, growth rate, maturity dynamics, and mortality are studied in Mediterranean horse mackerel Trachurus mediterraneus from the shelf zone of Crimea. The sex ratio is close to 1 : 1, the maximum body length of the females and males is 22.5 and 20.8 cm, respectively, and the maximum age of the representatives of both sexes is 6 years. The sexual dimorphism in the growth rate is not revealed. The von Bertalanffy growth equation parameters for both sexes are as follows: asymptotic length and weight 19.0 cm and 57.4 g and growth coefficient 0.44 year–1. The females (50%) reach sexual maturity by 10.72 cm, and the males reach maturity by 10.53 cm at the age 1+. The spawning is observed from June to September. The maximum values of gonadosomatic indeces of the males (2.37%) and females (3.84%) are registered in June, and July, respectively. The coefficients of the total, natural, and fishing mortality are 1.41, 0.89, and 0.52 year–1. Within the entire range, the strong positive relationships between maximum body length, linear growth rate index and mean annual surface water temperature are registered. The difference in horse mackerel growth rate between various regions of the Black Sea is small. Nevertheless, the growth rate and maximum body length of the Black Sea individuals are smaller than these parameters in the Mediterranean Sea that is connected with the adaptation of the Black Sea population to climate seasonality.

Age, growth and reproduction of the golden grey mullet, Chelon auratus (Risso, 1810) in the Golden Horn Estuary, Istanbul

AbstractAge, growth and reproduction biology of the golden grey mullet, Chelon auratus (Risso, 1810) have been studied in the Istanbul Golden Horn area. Fish length ranged from 13.4–46.8 cm, and age from 1–10 years, respectively. The sex ratio (female:male) was 1:1.08. The length-weight relationship was estimated as W = 0.0127L2.89, W = 0.0099L2.97 and W = 0.0156L2.82 for both sexes combined, females and males, respectively. The von Bertalanffy growth equation parameters were: L∞ = 57.52 cm, K = 0.1 year−1, t0 = −2.24 year for pooled data. The gonadosomatic index (GSI) values indicated the major spawning period was between August and November, and the minor spawning peak between March and April. The highest GSI values were observed in September. The length and age of sexual maturity were estimated as 26.2 cm and 4 years for males and 24.1 cm and 3 years for females.

Age, growth and sex of the shanny, Lipophrys pholis (Linnaeus, 1758) (Teleostei, Blenniidae), from the NW coast of Portugal

Age, growth, sex and gonadal maturation of the shanny, Liphorys pholis, were determined in specimens caught in a rocky intertidal area in northern Portugal in order to provide essential ecological data on the species. This study represents the first available reference in the literature for L. pholis in a southern European location. Totals of 251 individuals (115 females, 99 males, 37 undetermined; total length: 30–172 mm) were collected seasonally (November 2013, March, June, and September 2014) in a northern Portuguese rocky beach (Póvoa do Varzim: 41°23′47.79″N; 08°46′45.48″W) using fine-mesh aquarium fishnets during low tides. Marginal increment analysis showed that one translucent and one opaque zone was formed each year in the sagittal otoliths. Ages of L. pholis ranged from 0 to 6 years. Males were larger and older than females. The von Bertalanffy growth equation parameters considering all individuals were L∞ = 184 mm, K = 0.26 mm/year, t0 = −1.34. The annual variation of the fish condition and hepatosomatic indexes appeared to be related to the mobilization of the somatic reserves prior to reproduction. Maximum gonadosomatic index for males and females coincided with the breeding seasons (November and March). The sex ratio was close to 1:1, all maturity stages included. Furthermore, some stages of sexual development in males and females were observed during the same season, and several germinal cells were also observed at the same time within a single ovary or testis, indicating that L. pholis is an asynchronous and multiple spawner. Maturation for both sexes appears to be around 70 mm TL and prior to reaching 1 year of age.

Biological Characteristics of European Perch (Perca fluviatilis L., 1758) Inhabiting Lake Ladik (Samsun, Turkey)

Abstract The aim of this study was to determine the growth features of European perch (Perca fluviatilis L., 1758) inhabiting Lake Ladik. A total of 858 individuals were caught. The total length and weight ranged from 8.2 to 27.5 cm and from 7.16 to 365.20 g, respectively. The age of the females ranged between 1 and 7 years and the age of the males ranged from 1 to 5 years. The female to male ratio was 1:0.19. The von Bertalanffy growth equation parameters were determined as L ∞=41.27 cm, W ∞=1251.40 g, K=0.10 (year−1), t 0 (year)=−1.98 for all samples. Length-weight relationship was calculated as W=0.0047TL 3.358 for all specimens. Length-length relationships (total length-standard length, total length-fork length, standard length-fork length) were highly significant (r2>0.98). The mean condition factor value was obtained as 1.28 for all fish. Condition factor showed statistically significant increase according to length classes.

Age, growth, and reproductive biology of turbot, Scophthalmus maximus (Actinopterygii: Pleuronectiformes: Scophthalmidae), from the south-western coasts of Black Sea, Turkey

Background. The turbot, Scophthalmus maximus (Linnaeus, 1758), is of high economical value in Turkey and its biological characteristics have hitherto not been studied in the South-western Black Sea. The purpose of this study was to determine the age and growth, length–weight relation, condition factor, sex ratio, age and length at first maturity, and reproduction period of the turbot in the south-western Black Sea coast of Turkey. Materials and methods. Turbots were collected monthly in the south-western Black Sea coast of Turkey using bottom trawl and turbot gillnets. The fish samples were obtained between October 2004 and September 2005. Results. A total of 264 turbots were sampled and the age groups ranged from I to X (no individuals found at age group IX). Total lengths were between 14.0 and 70.0 cm, while weights varied from 34 to 5550 g. The length–weight relation for combined sexes was determined as W = 0.0085L3.1581. The von Bertalanffy growth equation parameters were: L¥ = 73.55 cm, k = 0.17 year–1, t0 = –0.12 year. The observed sex ratio (female : male) was 1 : 0.35. The length at first maturity (L50) of the species was 20.38 cm for females and 24.68 cm for males (both at two years old). Monthly gonadosomatic index (GSI) values suggest the spawning activity extends from 15 April to late June. Conclusion. The legal fishing season of the turbot, imposed in 2012, begins on 15 June. We recommend that this date should be postponed to 30 of June due to turbot’s reproduction extending to late June.

POPULATION STRUCTURE AND GROWTH OF RUDD Scardinius erythrophthalmus (L., 1758) FROM A EUTROPHIC LAKE IN NORTHERN ANATOLIA

A total of 1329 samples were collected from monthly sampling between November 2009 and October 2010 in order to analyze growth features and population structure of rudd Scardinius erythrophthalmus living in Lake Ladik which has eutrophic character. The fork length (FL) ranged from 9.8 to 21.4 cm and the body weight (W) ranged from 13.62 to 200.68 g. Based on lapillus readings, the maximum age was 7 years. The overall ratio of female to male was 1:0.16. The von Bertalanffy growth equation parameters were calculated as L∞ = 39.32 cm, W∞ = 1504.92 g, k = 0.08, t0 = -1.08 for females, and L∞ = 28.19 cm, W∞ = 448.03 g, k = 0.13, t0 = -1.19 for males. Length-weight relationship for females and males was found as W = 0.0060 FL3.386 and W = 0.0078 FL3.282, respectively. The Fulton’s condition factor (K) showed an upward trend with reference to age and length groups in both sex. The value of mean K was computed as 1.737 for females, 1.667 for males and 1.727 for combined sexes. This study provides the initial data on population structure, growth features and condition of rudd in Lake Ladik. Obtained data have shown that population is comprised of young individuals and that the growth rate of the species is slow.

Long‐Term Population Response of Triploid Grass Carp Stocked in Piedmont and Coastal Plain Reservoirs to Control Hydrilla

AbstractThe triploid Grass Carp Ctenopharyngodon idella has been used to control hydrilla Hydrilla verticillata infestations in southern U.S. reservoirs for several decades. After eliminating hydrilla in the water column, Grass Carp must be maintained in sufficient densities to control hydrilla regrowth from the tuber banks in the hydrosoil. We monitored the long‐term response of triploid Grass Carp populations that had eliminated hydrilla within the water column in two Piedmont (Lake Norman and Mountain Island Lake, North Carolina) and two Coastal Plain reservoirs (the Santee Cooper system comprising Lakes Marion and Moultrie, as well as the connecting canal in South Carolina). Triploid Grass Carp stocked in Lake Norman and Mountain Island Lake exhibited both slow growth and erratic, but potentially high, mortality. Due to erratic survival in the two Piedmont reservoirs, we could not estimate mortality using a catch curve. Fish stocked into the Santee Cooper system not only grew larger and faster, they also persisted (i.e., significant numbers of age‐16–21 fish were collected during sampling in 2011). We hypothesize that Piedmont reservoirs without hydrilla in the water column and with little naturally occurring aquatic vegetation have a very low carrying capacity for triploid Grass Carp. Consistent, long‐term survival of triploid Grass Carp in the Santee Cooper system may be due to available food provided by hydrilla regrowth in the water column, floating vegetation, and less‐palatable, native, submersed vegetation. Hydrilla management in systems with residual plant food could involve estimating an average mortality rate and maintaining enough fish (i.e., about one fish per four hectares of surface area) to control hydrilla regrowth. In Piedmont reservoirs, possible management alternatives could include maintenance stockings based upon (1) yearling stocking rates that were successful in the past, (2) stockings determined from indirect measures of mortality such as from von Bertalanffy growth equation parameters, or (3) stockings derived from measures or indices of abundance such as counts conducted at night by bowfishers.Received January 28, 2014; accepted April 20, 2014

Growth and mortality of two small fishes, Toxabramis swinhonis Günther, 1873 and Hyporhamphus intermedius (Cantor, 1842), in a Yangtze shallow lake (China) assessed by length frequency analysis

This study examined the growth and mortality of two widespread small fish species, Toxabramis swinhonis (Cyprinidae) and Hyporhamphus intermedius (Hemiramphidae), from a shallow lake (Niushan Lake, China) along the Yangtze River, by analyzing monthly length frequency data (July 2005 to June 2006) with the FAO-ICLARM stock assessment tool (FiSAT). Estimated von Bertalanffy growth equation parameters were: L (asymptotic length)=145mm TL, and K (growth coefficient)=0.66year(-1) for T.swinhonis; L=189mm TL, and K=0.68year(-1) for H.intermedius. The instantaneous rates of natural mortality (M) calculated for T.swinhonis and H.intermedius were 1.35 and 1.28year(-1), respectively. The length-converted catch curve method gave the total annual instantaneous mortality rate (Z) of 2.92year(-1) for T.swinhonis and 1.53year(-1) for H.intermedius. Recruitment patterns of both species were continuous, displaying a single major peak event per year. Despite not being of direct fishing interest, T.swinhonis, with high abundance and productivity as indicated by a high Z-value, can be an important species in fisheries management as an excellent food source for aquatic organisms, especially for larger fishes of economic value. These results represent the first information on population characteristics of T.swinhonis and H.intermedius, and constitute a comparison base for future growth studies in other lake environments.

Parámetros de crecimiento y variaciones de densidad de una población de Strombus gigas (Neotaenioglossa: Strombidae), del parque Xel-Ha área natural protegida

The queen conch, Strombus gigas, is a gastropod of commercial importance in the Caribbean. Population studies are based on size frequency analysis, using either length or weight parameters for the whole live organism. This contribution used mark-recapture data to estimate the Von Bertalanffy equation parameters and population number variation within a non harvest population from a protected area, to clarify the biometric parameters that better suit for the whole population, or for the juvenile and adult fractions. Conchs from Xel-Ha Park were monthly sampled from November 2001 to August 2005. Every conch found was measured and marked with a numbered tag that identified month and locality; and monthly abundance was estimated with Jolly's method. Length, lip thickness and weight increments were used to estimate the Von Bertalanffy growth equation parameters with Appeldoorn's subroutine of FISAT program. The population number varied through the study, with a minimum of 49 in April 2003 and maximum of 9 848 during June 2005. Conchs make only temporary use of Xel-Ha cove. Shell length gave the best fit for the juvenile fraction: L(infinity)=251, K=0.3, C=0.8 Wp=0.3; and lip thickness for adults: L(infinity)=47.78, K=0.17, C=0.1, Wp=0.86, while, the whole population was better represented by weight: L(infinity)=3850, K=0.36, C=0.8, Wp=0.3. A maximum age of 19 years was estimated from the population. Natural mortality was 0.49/year for juveniles and 0.29/year for adults. There were two pulses of recruitment: fall-winter and summer. It is concluded that population studies from length frequency data, should be analyzed independently in two groups, shell for the juvenile fraction and lip thickness for the adult fraction, or if it is not possible to analyze the population fractions separately, weight should be used to avoid miss calculation of the age structure.

Age and growth of the robust tonguefish Cynoglossus robustus in the Seto Inland Sea, Japan

This study provides data on the age and growth of the robust tonguefish, Cynoglossus robustus in the western part of the Hiuchi-Nada Sea in the Seto Inland Sea, Japan. Fish samples consisting of 299 robust tonguefish were collected monthly from June 2000 to May 2001. Maximum total length (TL) was larger for females than males. Growth was modeled using age estimates obtained from sagittal otoliths. The length–weight relationship followed an allometric growth pattern (b ≠ 3.0). Estimated ages ranged from 0.5 to 5.5 years for females and from 0.5 to 3.5 years for males. Von Bertalanffy growth equation parameters were derived from back-calculated TL fitted to TL at age; estimated values for females, were L∞=46.0 cm, k=0.278 year−1, and t0=−1.033 years, and values for males, were L∞=43.4 cm, k=0.281 year−1, and t0=−1.171. The growth performance index values for females and males were Φ=2.77 and Φ=2.72, respectively.

Dinámica poblacional y reproductiva de <i>Turbinella angulata</i> y <i>Busycon perversum</i> (Mesogasteropoda: Turbinellidae y Melongenidae) en el Banco de Campeche, México

Turbinella angulata and Busycon perversum are two marine gastropods that support the 90% of conch fisheries in the Gulf of Mexico, nevertheless there is no information available to support a management strategy for both species. The aim of this work was to obtain preliminary fishery information to promote management actions for both species in the Campeche Bank. The population of conchs was sampled in 12 transects (150x1.5m) by SCUBA diving from April 2008 to March 2010. All conchs were collected and siphonal length (SL) was measured. These samples were complemented with data from the commercial catches, analyzing a total of 2 832 individuals of T angulata. Siphonal length varied between 63 and 282mm. Sex ratio was of 0.98:1 female:male. The von Bertalanffy growth equation parameters were: L infinity =346mm; K=0.30 and t(0)=-0.24. Spawning extended from January to May with a long resting stage from June to September for over 80% of the adult population. The first gonadic maturity (L50) was at 210mm (SL) for females and 200mm for males. For B. perversum a total of 1655 individuals were analyzed. Siphonal length varied between 78 and 291mm with significant differences between male and female (p<0.05). Sex ratio was of 1:0.25 female:male. The growth parameters obtained were: Linifinity=360mm; K=0.35 and t(0)=-0.19. The spawning period was from August to December with resting stage from January to April. The L50 was 215mm (LS) for females and 190mm for males. Both species presented one recruitment pulse. These results will be useful to design management schemes based on population dynamics and reproductive attributes.

Age, growth, mortality and sex ratio of the inshore population of the edible crab, Cancer pagurus (Linnaeus 1758) in South Wales (UK)

Age, growth, and mortality of the edible crab, Cancer pagurus, were determined for the native population in South Wales (UK). Sampling was carried out on a monthly basis between February 2001 and September 2002. Carapace width ranged between 10.4 and 163 mm. Based on the carapace width frequency distribution, the Swansea and Gower population was composed mainly of males belonging to the first and second age-class (1 and 2), and of females belonging to the third and fourth age-class (3 and 4). Sex ratio was 1.126 ± 0.27 in favour of males. Carapace width frequency distributions and weight-at-age data were used to estimate the von Bertalanffy growth equation parameters. For the population as a whole, these were: L∞ = 199 mm, W∞ = 1179.56 g, K = 0.24 year−1, t0 = −0.1004 years. The overall carapace width–weight relationship was: W = 0.38(CW2.69). Analysis of covariance indicated a significant difference in the carapace width–weight relationship between males and females in the study area. Total mortality Z and natural mortality M rates for combined sexes were 1.245 year−1 and 0.567 year−1, respectively. The exploitation ratio E was estimated to be 54.43%.

Feeding ecology, growth and sexual cycle of the sand sole, Solea lascaris, along the Portuguese coast

Sand sole, Solea lascaris, were collected along the Portuguese coast, between October 2002 and July 2003, to examine feeding habits, age and growth and sexual cycle. The most important prey items were Mysidacea, Amphipoda and Polychaeta. Differences in diet according to season and length size were found: Amphipoda were very important in diet during winter, while Echinodermata were consumed mostly in summer; smaller individuals feed on Amphipoda while larger feed on Decapoda. Age of S. lascaris was determined from sagittae otoliths. The length of fish analysed ranged from 61 mm to 340 mm. The von Bertalanffy growth equation parameters differed significantly between sexes (L∞ = 342.3 mm, k = 0.50, t0 = −0.87 and L∞ = 264.5 mm, k = 0.82, t0 = 0.13, females and males, respectively). The highest values of the gonadosomatic index were obtained in winter and spring, when the highest proportion of individuals at spawning stage was recorded.

Age, Growth, and Age Structure of Amarillo Snapper off the Coast of Mazatlán, Sinaloa, Mexico

AbstractTo estimate age, describe individual growth, and determine the catch age structure of amarillo snapper Lutjanus argentiventris off the coast of Mazatlán, Sinaloa, artisanal fishery catches were sampled from December 2002 to November 2003. A total of 483 specimens were sampled that measured between 160 and 660 mm total length (TL) and had a total weight (TW) of between 60 and 4,685 g. The TL–TW relationship (TW = 0.0135TL3.03) showed isometric growth (slope b = 3.0; t‐test: P &gt; 0.05). From growth mark readings in 265 sagittal otoliths, 12 age‐groups between ages 1 and 17 were identified, and the predominant ages were 1–3 years. Monthly change in the otolith edge width allowed us to determine that growth marks had an annual periodicity; the formation of each growth mark ended in June, which coincided with the species' main spawning peak. Von Bertalanffy growth equation parameters estimated from age–TL data were 735 mm for asymptotic length (L∞), 0.097 per year for the growth coefficient (K), and −2.05 years for age at a TL of zero (t0). The age composition of the catch indicated that 95% of specimens were between ages 1 and 5 and 80% of specimens were younger than age 4 (the age at which 50% of the population reproduces for the first time). Age‐6 amarillo snapper had a reduced importance, not exceeding 5%. This study is the first that uses otoliths for determining age and describing growth of the amarillo snapper.

Differences in the exploited oyster (Crassostrea virginica (Gmelin, 1791)) populations from different coastal lagoons of the Gulf of Mexico.

1 - Oyster fishery is one of the most important coastal fisheries of Mexico. Production from the Gulf of Mexico coast makes up 93.4% of national production; during 2000-2002 it reached over 49,000 mT, with value of 9.2 to 15.5 million USD. Production is based on enhanced beds management. It is an activity of social importance, as many coastal communities find their income and work opportunities in it. In the state of Tabasco there are 1,371 oyster fishers in 14 cooperative societies, and 3,000 shuckers. There is an extensive bed management activity with seeding of collected spat and shell laying. Although a minimum legal size of 80 mm is required, it is not observed. 2 - We identified the growth equation parameters for size structure data for five beds from three lagoons. Maximum height varied between 118 and 140 mm with means between 58 and 63 mm. The von Bertalanffy growth equation parameters were L$∈fty$ between 124 and 154 mm, with K between 0.71 and 1.21. In most cases a significant influence of seasonality was detected, mostly during winter, but at some localities it was during summer. Total mortality Z varies from 1.64 to 2.39. As no data on natural mortality M were available we applied 25, 50 and 75% of Z to M, which allowed us to model the behaviour of the populations under different rates of fishing mortality F and the impact of different M in yields. 3 - We conclude that the populations are over exploited in size and this is affecting yields. Besides, the populations are at risk of collapse if natural mortality increases awing to any environmental impact. It is recommended to increase mean size to 90 mm which means a minimum catch size of over 70 mm, as required by the official norm, this would increase yields in weight 100% and there would be a significant number of organisms to buffer any increase on natural mortality.

Feeding ecology, age, growth and sexual cycle of the Portuguese sole, Synaptura lusitanica

Portuguese sole, Synaptura lusitanica, were collected from the Portuguese coast, between April 2001 and March 2002, to examine feeding habits, age and growth, and sexual cycle. Synaptura lusitanica fed on few prey items, its diet mainly composed of polychaeta, bivalvia and cephalochordata. Significant differences were found between the proportion of prey items according to season, length class of fish and coastal area. The main differences related to fish size were the higher ingestion of bivalvia by larger fish, in the west coast area, and the increase in the important cephalochordata for fish larger than 300 mm total length, in the south coastal areas. Polychaeta presented a lower importance in the spring–summer period while bivalvia increased its values in the autumn–winter period. Cephalochordata were more important in the autumn–winter period, but only for fish larger than 300 mm total length and in the south coastal areas. Vacuity was extremely high (mean value of 52%). Ages of S. lusitanica were determined from sagittae otoliths. The length of fish analysed varied from 157 mm to 480 mm, and the oldest fish was age 8. The von Bertalanffy growth equation parameters differed little between sexes, being the asymptotic length obtained for females higher compared to males. The highest values of the gonadosomatic index were obtained in summer, which was the period when the highest percentage of individuals in the spawning stage were recorded. Therefore, the spawning season seems to be from mid-spring (May) until the end of summer (September).

Growth of the purple snail Plicopurpura pansa in Baja California Sur, Mexico

To study the growth of the purple snail Plicopurpura pansa at the northern limit of its distribution, from 1999 to 2001 monthly random samples were obtained from two beaches in the southern part of the Baja California Peninsula (Mexico): one on the Gulf of California and the other on the west coast of the peninsula. Mark and recapture experiments, as well as laboratory rearing were also done. The von Bertalanffy growth equation parameters derived from length frequency data were K = 0.17 and L∞ = 90 mm, and agree with those estimated from the mark and recapture data, but are lower that those reported in the literature for P. pansa from the central and southern Mexican Pacific. Snails maintained under laboratory conditions had low growth rates. These results could be used to implement models for the assessment of purple snail fisheries.

Growth, Natural Mortality, and Predicted Response to Fishing for Largemouth Bass and Smallmouth Bass Populations in North America

Abstract Growth, natural mortality, latitude, elevation, average air temperature, and degreedays exceeding 10°C were summarized for 698 populations of largemouth bass Micropterus salmoides and 409 populations of smallmouth bass M. dolomieu in North America and used in simulations to determine the effects of fishing on populations of varying productivity. Length at age and von Bertalanffy growth equation parameters varied greatly among populations and resulted in ages at quality length (300 mm for largemouth bass and 280 mm for smallmouth bass) ranging from 1 to 10 years for largemouth bass and from 2 to 9 years for smallmouth bass. Natural mortality also varied widely, but the conditional annual rate averaged 35% for both species. Age at quality length was used as an index of growth rate and was positively correlated (P < 0.05) with latitude and elevation for largemouth bass and with latitude for smallmouth bass. Age at quality length was negatively correlated (P < 0.05) with mean air temperature and degr...

Reproductive biology and growth of the goatfish, Parupeneus barberinus (Lacepede), in Aqaba, Jordan

Monthly changes in the gonadosomatic index indicate that the main spawning season of Parupeneus barberinus in Aqaba extends from May to August for females and from May to June for males. Males in the 4 years age‐group (63–4%) and the 5 years age‐group (65–1%) are predominant. The von Bertalanffy growth equation parameters calculated from mean total length data are: Lα= 32–8cm; K=0–225; (to=−0–73 for males and Lα= 32–7cm; K=0–206; to=−0.82 for females. The length‐weight regression coefficients for males (2.85) and females (2.8) are not significantly different and they indicate a negative allometric growth. There is no significant change in condition factor with age.

Studies on growth rate of yellow notothenia, Notothenia gibberifrons Lönnberg, 1905 off South Georgia

The paper demonstrates that scales are not suitable for back readings, due to a poor legibility of their central parts, the peripheral regions being poorly legible in older fish scales as well. One can presume that the scales begin to grow as late as in the second year of life. Most otoliths (sagitta) can be used in back calculations. Based on measurements of radii of various growth zones on the otolith cross-section, mean lengths attained in subsequent years of life were calculated. The von Bertalanffy growth equation parameters were estimated as follows: L&#8734; = 57.48 cm; K = 1.04; t0 =0.439 yr. The mean length at first maturity was estimated at 37.5 cm, i.e., 65% of L&#8734;.