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.     

Age, growth and mortality of the Mediterranean amberjack Seriola dumerili (Risso 1810) from the south-eastern Adriatic Sea

The age, growth and mortality of the Mediterranean amberjack Seriola dumerili (Risso 1810) were determined in 298 specimens collected in the south-eastern Adriatic Sea (Donji Molunat Bay) from 17 May to 26 June 1997. The total length ranged from 32.0 to 160.0 cm and weight from 0.5 to 46.5 kg. Ten age classes, ranging from 1° to 10° years were defined by scale readings. Mean total length and weight-at-age data were used to estimate the growth parameters of the von Bertalanffy equation: L _∞=174.6 cm, K =0.190, t ₀=–0.314; W _∞=79.01 kg, K =0.139 and t ₀=–0.746. The length–weight relationship was estimated at: W =0.000123 ×  L ^2.847. The overall sex ratio was 1 : 1.06 in favour of males. Total ( Z ) and natural ( M ) mortality were found to be 0.41 years⁻¹ and 0.30 years^–1, respectively. The exploitation ratio ( E =0.27) indicates that the fishing pressure on the Mediterranean amberjack was low in the investigated region.     

Reproduction, age, growth and mortality of axillary seabream, Pagellus acarne (Sparidae), from the Canarian archipelago

Axillary seabream Pagellus acarne (Risso 1826) caught off the Canary Islands from January 1991 to December 1994 were studied. The length range of the catches was between 11 and 31 cm, with a modal distribution between 17 and 21 cm. The overall ratio of males to females was 1:1.74. Males were observed up to a length of 24 cm. Hermaphrodites were recorded at lengths between 15 and 23 cm. The species was characterized by protandric hermaphroditism. The reproductive season extended from October to March, with a peak in spawning activity in December–January. The size at sexual maturity was 15.8 cm total length (2 years old) for males and 19.4 cm total length (3 years old) for females. The total length–total weight relationship for the entire population is described by the parameters a = 0.0068, and b = 3.2401. Otolith age readings showed that the population exploited consisted of 10 age groups (1–10 years), including a very high proportion of individuals between 1 and 4 years old. The von Bertalanffy growth parameters for all individuals were L_∞ = 32.98 cm, k = 0.22 years⁻¹, and t₀ = −0.87 years. Males grew comparatively slower than females. The instantaneous rates of mortality for all fish were Z = 0.96 years⁻¹, M = 0.30 years⁻¹, and F = 0.66 years⁻¹. The exploitation ratio and the length at first capture were, respectively, E = 0.69 and LC₅₀ = 16.1 cm. The stock is overexploited, therefore measures such as closed seasons or changes in fishing patterns would be desirable to safeguard the spawning stock and recruits.     

Age, growth and feeding of the common stingray (Dasyatis pastinaca, L., 1758) in the Cilician coastal basin, northeastern Mediterranean Sea

Growth and feeding of stingray ( Dasyatis pastinaca ) were studied using 346 specimens from the Cilician Basin coastal area (northeastern Mediterranean). Age classes between 0 to XII were found. The total length of all specimens ranged from 14.6 to 100.9 cm, and total weight was between 22.5 and 6800 g. Total length (TL)-weight (W) and disc width (DW)-weight (W) relationships were W = 0.0033*L^3.1429 and W = 0.0039*DW^3.4914, respectively. The age data, derived from central readings, were used to estimate the von Bertalanffy length and weight growth parameters. The results were L_∞ = 294.9 cm, W_∞ = 198690.1 g, K = 0.029 year⁻¹; t₀ = −2.2 year. The D. pastinaca diet was composed mainly of crustaceans.     

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: L_α= 32–8cm; K=0–225; (t_o=−0–73 for males and L_α= 32–7cm; K=0–206; t_o= −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.     

Differences in size and growth rates of male and female migrating Japanese eels in Pearl River, China

The Sr/Ca ratios in otoliths of silver Japanese eels Anguilla japonica , in Pearl River, China, indicated that both sexes did not stay in brackish water and grew in fresh water from the glass eel stage until spawning migration. This did not support the hypothesis that females tended to distribute upstream and males might be restricted to estuaries. The back-calculated total length of males at glass eel stage was not significantly different from that of females, indicating that the hypothesis that small glass eels became males and larger ones became females may not be true. The mean (±S.D.) age and total length of males at migration were 6·4±1·6 years and 48·3±4·5 cm, which were significantly smaller than for females, 8·3±1·6 years and 61·4±4·1 cm. The age of migration was related inversely to growth rate for both sexes. Growth parameters of the von Bertalanffy growth equation were K =0·21 cm year°1, L _∞=55·7 cm and t _o=-0·55 year for males and K =0·14 cm year⁻¹, L _∞=77·5 cm and t _o=-0·60 year for females. The difference in asymptotic length ( L _∞) between males and females may be because females postpone migration to achieve larger size for maximizing reproductive success.     

The population biology of tench, Tinea tinea (L.), in two gravel pit lakes

The populations of tench from two gravel pit lakes of contrasting habitat type were studied. The population density of tench from St Peter's Lake, which has abundant aquatic vegetation was 176 individuals ha⁻¹ (102.2 kg ha⁻¹) compared to 0.3 individuals ha⁻¹ (0.5 kg ha⁻¹) in the Main Lake which has very little aquatic vegetation. The results of ageing tench by scales, opercular bones and otoliths were compared; all three structures gave similar results up to 9 years of age, but thereafter there were difficulties in ageing using scales and care was needed in counting annuli. The oldest tench caught was 15 years old. Growth of male and female tench was similar and fitted the von Bertalanffy model; for female tench L_∞ = 573 mm, K =0.122 and for male tench L_∞ = 586 mm, K =0.114. Recruitment was variable and strong year classes occurred in years with warm summers.     

Biometrics of Sardinella longiceps Val. in relation to upwelling in the Gulf of Aden

Growth, size composition, condition factor and gonad index of the oil sardine, Sardinella longiceps Val., oscillated over an annual cycle in relation to upwelling. Growth in length was modelled using the formula of Pauly & Gaschütz (1979): where L _t= length cm at age t years, L_∞= 23.8cm, K=0.97, t_o=0.70, C=1.08 and t_s=−0.08. The relationship of growth rate, spawning, and condition factor, to upwelling and plankton blooms is discussed.     

Growth rates of Lutjanidae (snappers) in tropical Australian waters

Growth rates of three commercial species of Lutjanidae were estimated from sections of vertebrae cross-checked with scales. The von Bertalanffy growth constants for Lutjanus malabaricus were K =0.168, L_∞ =70.7 cm standard length (S.L.). For Pristipomoides multidens these were K = 0.219, L _∞= 59.1cm, and for Pristipomoides typus K =0.254, L _∞= 51.5 cm. Length/weight was analysed in the form W= aL^b where W was fresh weight (g) and L = S.L. (cm). The constants were: L. malabaricus, a = 0.041, b = 2.842; P. multidens, a =0.032, b = 2.897; P. typus, a = 0.038, b = 2.822. The growth rates were considered low in comparison with demersal fish counterparts from temperate seas.     

Age, growth, reproduction and mortality of the striped seabream, Lithognathus mormyrus (Pisces, Sparidae), off the Canary Islands (Central-east Atlantic)

Striped seabream, Lithognathus mormyrus L. (n=731) caught off the Canary Islands from January 1999 to June 2000 were studied. Fish ranged in size from 113 to 372 mm total length, weighing from 21.1 to 748.2 g total weight. Weight increased allometrically with size (b=2.9071). Fish age was 0–10-years-old. Growth was relatively slow (k=0.88 years⁻¹), with females growing at a slightly faster rate than males. The species displayed protandric hermaphroditism. Male : female ratio was unbalanced in favour of males (1 : 0.85). Males predominated in smaller sizes, females in larger sizes, and intersexual individuals were in intermediate sizes. The reproductive season extended from June to December, with a peak in spawning activity in August–September. Males reached maturity at 207 mm (2 years) and females at 246 mm (3 years). The real value of instantaneous rate of natural mortality was between 0.30 and 0.45 years⁻¹.     

Reproduction, age and growth of Sillago maculata in south-eastern Australia

Sillago maculata is endemic to the east coast of Australia where it is harvested by recreational and commercial fishers; however, little is known of the important aspects of its biology and ecology to assist with fisheries management planning. This situation is redressed here by investigating aspects of the reproduction, age and growth of estuarine populations of S. maculata in south-eastern Australia. Gonadosomatic index (GSI) values indicated peak spawning occurred between September and February and that the estimated mean fork length at maturity (L₅₀) was 14.6 cm for males and 15.2 cm for females. Females displayed an asynchronous pattern of oocyte development, with individuals probably spawning multiple times in a spawning season. A validated aging protocol using thin sectioned otoliths was used to estimate the age of fish. The maximum ages for males and females were 9.5 and 12.0 years, respectively. Growth differed between sexes, with males ( L ∞ = 24.04, K  = 0.70, t ₀ = −0.09) attaining a smaller maximum length than females ( L ∞ = 25.01, K  = 0.72, t ₀ = −0.04). The age composition of gill-net and beach-seine samples mainly consisted of individuals aged 2–4 years, and there was evidence of variable recruitment. Management implications are also discussed.     

Spawning period and growth of yellowfin bream, Acanthopagrus australis (Günther), in Moreton Bay, Australia

Monthly changes in the gonosomatic index indicate that yellowfin bream, Acanthopagrus australis , in Moreton Bay have a short spawning season with a peak during the period July to August each year. The growth rate of A. australis was estimated from tag-recapture data and by length-frequency analysis. Modes representing age classes 0, I and II often appeared in length-frequency distributions, however modes for older age classes were difficult to identify. The von Bertalanffy growth curve parameters calculated from release–recapture data are: L_∞ = 29.5 cm; K = 0.51; t ₀=– 0.32 years.     

Age, growth and reproduction of the black scorpionfish, Scorpaena porcus (Pisces, Scorpaenidae), on the Black Sea coast of Turkey

Age, growth and reproduction of the black scorpionfish, Scorpaena porcus were studied in specimens from the coast of the Sinop Peninsula (Black Sea) between March 2002 and April 2003 in order to characterize these population parameters in comparison to specimens from populations of nearby regions. A total of 1086 specimens was captured by beam trawl at the depths between 0 and 30 m. The total number of females (510) was significantly higher than that of males (373). Total length of males and females ranged between 5.7 and 23.6 cm, and 4.9 and 31.7 cm, respectively. The length–weight relationship showed a positive allometric growth. Females grew faster and reached a larger size at age than males ( L _∞ = 111.9 cm, K  = 0.035 year⁻¹, φ' = 2.64 for females, and L _∞ = 74.6 cm, K  = 0.054 year⁻¹, φ' = 2.49 for males). The age range estimated was up to 8 years for females and 5 years for males. Reproduction likely occurs between June and September. Sex ratio varied greatly with season, perhaps indicating different seasonal migratory patterns in adults of different sex. An inverse correlation between gonadosomatic index (GSI) and hepatosomatic index (HSI) was evident during the reproduction seasons. The mean size at first sexual maturity was 17.5 cm TL for females, and 16.7 cm TL for males.     

Biology of the salema, Sarpa salpa (L. 1758) (Pisces, Sparidae) from the middle-eastern Adriatic

Salema Sarpa salpa (Linnaeus, 1758), were caught in the middle-eastern Adriatic Sea from August to November 2004. Length range of the samples was between 10.3 and 43.9 cm, with mean values of 25.5 cm in males, 32.6 cm in females, and 11.4 and 20.2cm in immature and hermaphrodite specimens, respectively. Sex ratio (males : females) was 3.1 : 1. Males were observed up to 37 cm length. Hermaphrodites showed lengths between 18 and 21 cm. The species was characterized by protandric hermaphroditism. Size at sexual maturity was 20.6 cm (2 years old) for males. Total length-total weight relationship for the entire population is described by the parameters a  = 0.00893, and b  = 3.1055. Otolith age readings showed that the population consisted of 15 age groups (1–15 years), including a very high proportion of individuals 1–7 years old. The von Bertalanffy growth parameters were L _∞ = 33.11cm, k  = 0.514, and t ₀ = −0.392 years for males and L _∞ = 40.85cm, k  = 0.179, and t ₀ = −2.606 years for females. Survival rate of females ( S  = 0.870) was much greater than for males ( S  = 0.769).     

Population variables and life-history characteristics of the alligator pipefish Syngnathoides biaculeatus, in Papua New Guinea

Population structure and life-history variables of the widely distributed alligator pipefish Syngnathoides biaculeatus were characterized in Bootless Bay, Papua New Guinea over the course of 11 months. There was little evidence of seasonality with four focal populations showing no significant change in abundance. Similarly, the sex ratio remained 1:1 for all but 1 month. Reproductive males carrying eggs (148–278 mm in total length, L _T) were found in all months. Brood size was significantly, positively related to male L _T for newly laid broods only. Maximum observed brood size was 351 and mean ± s . d . brood size was 238 ± 57 for newly laid broods. Juveniles and males showed no change in mean L _T over the year while slightly smaller females were captured in November 2006 and September 2007. Males were significantly longer than females so von Bertalanffy growth coefficients were estimated separately for each sex: males L _∞= 285 mm, K = 0·82 year⁻¹ and females L _∞= 261 mm, K = 1·10 year⁻¹. These estimates suggest that this species grows rapidly and has a short-life span. In the context of growing concern about overexploitation of syngnathids, a rapid growth rate combined with year round reproductive activity suggests that the tropical S. biaculeatus may be relatively resilient with regard to fishing pressure.     

Ecology and exploitation pattern of a landlocked population of sand smelt, Atherina boyeri (Risso 1810), in Trichonis Lake (western Greece)

Age, growth, mortality and exploitation pattern of sand smelt, Atherina boyeri (Risso 1810), in Trichonis Lake (western Greece) were studied from samples taken from catches of local fishermen. Individuals ranged between 44 and 109.53 mm in total length (TL). Age determinations based on scale readings show that the population has a 4-year life cycle. Sand smelt grows allometrically (b=3.18) and relatively rapidly, achieving 52.3% of the growth during the first year; thereafter the annual growth rate drops quickly. The von Bertalanffy growth parameters for all individuals are: L_∞=112.40 mm, k= 0.42 years⁻¹και t_o=−0.40 years. The total mortality rate was Z=1.65 years⁻¹ and the natural mortality rate M=1.07 years⁻¹. The exploitation rate indicates that the population is rather underexploited (E=0.35).     

Age, growth and mortality of picarel, Spicara smaris L. (Pisces: Centracanthidae), from the eastern Adriatic (Croatian coast)

Age, growth and mortality of picarel Spicara smaris L. collected in the eastern middle Adriatic during April and May in 1999 were studied. The total lengths of individuals ranged from 6.3 to 19.8 cm, and the weight from 2.2 to 78.3 g. The slopes ( b values) of the total length–weight regressions indicated negative allometric growth for females ( b =2.8± 0.03) and isometric growth for males ( b =3.08±0.04). The oldest female and male were 4 and 6 years, respectively. The von Bertalanffy growth parameters for the sexes combined were ( L _∞=22.76 cm, K =0.277, t ₀=−0.793). The overall sex ratio was 1 : 4.1 in favour of females. Individuals larger than 17.9 cm were all males.     

Growth, diet and metabolism of common wolf–fish in the North Sea, a fast–growing population

The von Bertalanffy growth parameters for common wolf–fish Anarhichas lupus in the North Sea were: male: L ∞=111·2 cm, t ₀=–0·43 and K =0·12; and female: L ∞=115·1 cm, t ₀=–0·39 and K =0·11, making this the fastest growing stock reported. Resting metabolic rates (RMR±S.E.) and maximum metabolic rates (MMR±S.E.) for six adult common wolf–fish (mean weight, 1·39 kg) at 5° C were 12·18±1·6 mg O₂ kg^–1 h^–1 and 70·65±7·63 mg O₂ kg^–1 h^–1 respectively, and at 10° C were 25·43±1·31 mg O₂ kg^–1 h^–1 and 113·84±16·26 mg O₂ kg^–1 h^–1. Absolute metabolic scope was 53% greater at 10° C than at 5° C. The diet was dominated by Decapoda (39% overall by relative occurrence), Bivalvia (20%) and Gastropoda (12%). Sea urchins, typically of low energy value, occupied only 7% of the diet. The fast growth probably resulted from summer temperatures approximating to the optimum for food processing and growth, but may have been influenced by diet, and reduced competition following high fishing intensity.     

Growth in the crayfish Austropotamobius pallipes (Crustacea: Astacidae)

SUMMARY. The growth of Austropotamobius pallipes was studied in the River Ouse during 1976–78. Growth of mature crayfish (>2.5 cm carapace length) was followed by determining the relationship between the growth increment at moult and premoult carapace length, together with the frequency of moulting of different categories of crayfish. These data are supplemented by the recapture of marked individuals and the measurement of crayfish held in corves in the river. Growth was limited to the period May–October when water temperatures exceeded 10°C. Growth rates of male and female crayfish are similar until maturity is reached, thereafter males moult twice per year and the majority of females moult once. No crayfish in excess of 3.7 cm carapace length has been observed to moult more than once per year. Growth of juveniles (<2.5 cm carapace length) was estimated from size frequency distributions constructed from regularly taken samples. Growth rates of juveniles showed great variation both between and within year classes. In the hot dry summer of 1976, juveniles exhibited faster growth rates (instantaneous growth rates (G) for 0+ and 1 + crayfish were 0.029 and 0.013 mg mg⁻¹ day⁻¹. respectively) than in other years. Laboratory experiments on the effect of temperature on the growth rate of 0 + crayfish were undertaken; for crayfish at 15°C. G = 0.0138 (0–53 days) and at 10°C, G = 0.0003 (0–90 days). Crayfish held at 10°C failed to undergo a single successful moult. At 20°C crayfish exhibited exponential growth over the first 40 days, with G = 0.0189. declining thereafter to G = 0.012 (40–90 days).     

Age, growth, sexual maturity and food composition of Sciaena umbra in the south-eastern Black Sea, Turkey

Studied were the age, growth, maturity and food composition of the brown meager, Sciaena umbra, caught off Trabzon, south-eastern Black Sea (Turkey) in 2002–2003. A total of 329 individuals was collected by spear fishing and hand nets. The thin sectioning method was used for aging the fish otoliths. Fitted von Bertalanffy growth parameters for all fish were: L _∞ = 51.14 (±1.19) cm, k  =   0.27 (±0.02) year⁻¹ and t ₀ = −0.93 (±0.07) year. This study revealed that S. umbra is a relatively slow-growing and long-lived species with a life span in excess of 18 years. Sexual maturity begins when they reach a length of about 15 cm. Lengths at which 50% of brown meagre become mature are 19.50 for males and about 22 cm for females. Spawning begins in June, when the temperature is approximately 18°C, and ends in August. Gut content analysis indicated that this species feeds mainly on crustaceans, then switches to fish as they grow. Sciaena umbra appears to be an apex predator in the upper littoral zone.