Regional size, age and growth differences of red grouper (Epinephelus morio) along the west coast of Florida

Red grouper (Epinephelus morio) were collected from the west coast of Florida, the central area of fishery harvest in U.S. waters, by fishery-dependent sources during 2000–2005. The west Florida shelf was divided into two regions: north (capture locations ≥28°N latitude) and south (capture locations <28°N latitude). Significant differences were found for age, length, and size-at-age by region and by gear; red grouper from the north were significantly younger and smaller on average than those from the south. Regional differences were also noted with respect to age progression; year class trends were only detected in the north. The 1996 year class dominated the landings in 2000–2001 (ages 4 and 5) and the 1999 year class dominated in 2004–2005 (ages 5 and 6). Regional data were fit to a size-modified von Bertalanffy growth model indicating smaller asymptotic length (L_∞) and faster growth rate (k) in the north (north: L_∞ = 800 mm, k = 0.23 mm year⁻¹, t₀ = 1.12; south: L_∞ = 863 mm, k = 0.15 mm year⁻¹, t₀ = 0.05). Mortality estimates derived from catch curves resulted in higher total and fishing mortality in the north for both gears. Alternative explanations of regional differences likely depend on nursery delineation and correlation to periodic environmental events such as red tides and hurricanes; all possibly important factors based upon anecdotal information. Nevertheless, our finding of regional demographic differences in red grouper from the west coast of Florida suggests a more complex population spatial structure for red grouper.     

Age,growth and maturation of the redbelly tilapia <Emphasis Type="Italic">Tilapia zillii</Emphasis> introduced into the Haebaru Reservoir on Okinawa-jima Island

ABSTRACT:   The age, growth and maturation of the redbelly tilapia Tilapia zillii introduced into the Haebaru Reservoir on Okinawa-jima Island were studied using 2197 specimens ranging from 7.3 to 168.0 mm standard length (SL). The spawning season was estimated to be from April to August, with a peak in April and May. The first maturation sizes of females and males were estimated to be 38.1 and 33.0 mm SL, respectively. The opaque zones in otoliths that form annually were found to correlate with the spawning season. Maximum ages of females and males were 7 and 6 years, respectively. The von Bertalanffy growth formulae were expressed as: L _t  = 99{1 − exp[−0.67( t  + 0.09)]} for females and L _t  = 155{1 − exp [−0.36( t  + 0.12)]} for males. Males grew to be larger than females from the first year onward. Populations of this species are characterized by early maturation life history parameters and are thought to adapt and become established quickly after being released into new water systems. Furthermore, extermination activity in winter is thought to be an effective strategy before the newly recruited fish begin breeding in the warmer months.     

Age,growth and age at sexual maturity of fan ray <Emphasis Type="Italic">Platyrhina sinensis</Emphasis> (Batoidea: Platyrhinidae) in Ariake Bay,Japan

Abstract:   Age, growth and sexual maturity of the fan ray Platyrhina sinensis in Ariake Bay, Japan were determined from specimens collected from May 2002 to September 2006. Age determination was conducted by vertebral centrum analysis using soft X-radiography. Annual band pair deposition was determined by marginal increment and edge analyses. The von Bertalanffy growth model best described the overall pattern of growth for both males and females (males L _∝  = 455.2, k  = 0.56, t ₀ = −1.09; females L _∝  = 555.8, k  = 0.28, t ₀ = −1.77; L _∝ is the theoretical asymptotic total length in mm, k is the growth rate coefficient and t ₀ is the theoretical time at zero length). Parameter estimates suggest that females attain a larger asymptotic total length and grow more slowly than males. The observed maximum ages were 5 years for males and 12 years for females. Age at 50% sexual maturity was 2.1 years for males and 2.9 years for females. The results indicate that this species is relatively fast-growing, short-lived and early maturing compared with many batoid species.     

Female-biased mortality rate and sexual size dimorphism of migratory masu salmon, Oncorhynchus masou

Abstract –  We examined whether mortality and growth during the migration phase (the lacustrine phase after smolting) differ between sexes in migratory (lake-run) masu salmon ( Oncorhynchus masou ) in a lacustrine population, northern Hokkaido, Japan. The sex ratio of 1+ smolts was more skewed to females than that of the returning adults in three annual cohorts examined, indicating that females have a higher mortality rate during the migration phase. Although there was no difference in smolt length between sexes, female adults were larger in body length than males of the same age: female-biased sexual size dimorphism (SSD) occurs. We suppose that breeding selection favouring a larger body size for females than for males in this population probably requires that females undertake more intensive foraging behaviour with its greater inherent risks but faster growth rates during the migration phase. It therefore seems to be likely that the selection is the ultimate cause of the female-biased mortality rate and SSD.     

Growth and reproduction of the red frog crab, <Emphasis Type="Italic">Ranina ranina</Emphasis> (Linnaeus, 1758), in the Andaman Sea off Thailand

ABSTRACT:   Studies were conducted on growth and reproduction of the red frog crab, Ranina ranina (Linnaeus, 1758), in the Andaman Sea off Thailand from 1998 to 1999. Samples were collected from Ko Similan, Ko Surin and Thai-Myanmar boundary waters by gill net. Results showed that the relationship between carapace length (CL) and body weight (BW) for males (CL, 5.84–14.10 cm) was BW = 0.2598 CL^3.0931, and for females (CL, 5.35–10.97 cm) was BW = 0.4280 CL^2.8656. Growth in each gender showed allometric growth. The average CL of males was significantly larger than that of females. Average male and female crab sizes in 1999 were smaller than in 1998. The spawning season was found to be from November to February; maturing male crabs were abundant from September to December. Average sizes of CL at first maturity for males and females were 7.44 and 7.22 cm, respectively. Fecundity ranges of ovigerous female crabs were 74 600–167 900 eggs with an average egg diameter of 0.62 mm. The monthly sex ratios (male : female) varied between 1:0.56 and 1:2.77.     

Reproductive biology of <Emphasis Type="Italic">Sillago aeolus</Emphasis> in Okinawa Island,Japan

ABSTRACT:   A total of 414 fish (female, 59.3–275.0 mm and male, 61.0–220.0 mm standard length) were collected from December 2000 to March 2002 around Okinawa Island, Japan, for the determination of sex, spawning season, maturity and fecundity. Monthly changes in the gonadosomatic index (GSI) exhibited similar trends for both sexes and the mean GSI maintained a high level between February and May. Furthermore, the percentage frequency of hydrated oocytes and the spermatozoic activity suggested that main spawning occurred between February and May. Some hydrated oocytes were found throughout the year, with a GSI value greater than 1.0, suggesting that sporadic spawning occurred. Length at first maturity was determined for females and males as 120 and 113 mm standard length, respectively. Almost 50% and 100% males were matured at the end of their 0 and 1 year of age group, respectively. In contrast, no females were found to be mature at 0+ age group, and almost 60% of females were mature at 1+ age group. At ages over 2 years, all males and females were found to be mature. Batch fecundity (BF) of 33 females was related to standard length, and the relationship between standard length and BF was expressed by the exponential equation: BF = 269.5e^0.020954SL.     

Age, growth, and reproduction of silky sharks, Carcharhinus falciformis, in northeastern Taiwan waters

To examine the age, growth and reproduction of silky sharks, Carcharhinus falciformis, in the waters off northeastern Taiwan, 469 specimens (213 females and 256 males) were collected from August 2000 to January 2002 at the Nanfanao fish market, northeastern Taiwan. The relationship between body weight (W) and total length (TL) for both sexes combined was expressed as: W = 2.92 × 10⁻⁶ TL^3.15 (n = 469, p < 0.01). The relationship between TL and vertebral centrum radius (R) for both sexes combined data was estimated as: TL = 25.979 + 18.197R (n = 250, p < 0.01). Growth bands (including translucent and opaque zones) in precaudal vertebrae formed once a year between December and January and were counted up to 11 and 14 for females and males, respectively. The von Bertalanffy growth function (VBGF) was used to model the observed length at age data. The sexes combined VBGF predicted an asymptotic length (L_∞) = 332.0 cm TL, growth coefficient (k) = 0.0838 year⁻¹, age at zero length (t₀) = −2.761 year (n = 250, p < 0.01). Size at 50% maturity for males was estimated to be 212.5 cm based on the logistic curve, which corresponded to 9.3 years. Females matured at 210–220 cm, which correspond to 9.2–10.2 years. The length at birth was estimated to be 63.5–75.5 cm TL. The number of embryos per litter was 8–10 and sex ratio of embryos was 1:1.     

Seasonal distribution, age, growth, and reproductive biology of marbled sole Pleuronectes yokohamae in Tokyo Bay, Japan

ABSTRACT:   The seasonal distribution, age, growth and reproductive biology of marbled sole Pleuronectes yokohamae (Günther) from Tokyo Bay, Japan were studied. A clear seasonal distribution trend was observed, with P. yokohamae limited to the south of the bay in summer and expanding almost throughout the bay in other seasons. The formation and dynamics of hypoxic areas in the bay limited the northward distribution of P. yokohamae in summer. Age was determined by counting growth rings on otoliths; maximum ages were found to be 5 years for males and 6 years for females. The mean back-calculated length for females at each estimated age was greater than that for males. Growth of males and females was shown by the von Bertalanffy growth equations. Reproductive biology was studied on the basis of gonadosomatic indices and histological sections of gonads. The spawning season lasted from November to March, peaking in December and January. Sixty per cent of males at 1 year and all males ≥ 2 years had mature testes, whereas 6.7% of females at 1 year, 58.3% of females at 2 years, and all females ≥ 3 years had attained maturity.     

Population age and sex structure of Aphanius fasciatus Nardo, 1827 (Pisces: Cyprinodontidae) in the Mesolongi and Etolikon lagoons (W. Greece)

The population structure of Aphanius fasciatus in the Mesolongi and Etolikon lagoonal system was studied, using 5794 fish. Significant differences were observed in the number of individuals of each sex, the age and size composition and survival. The overall males to females sex ratio was 1:2.44, although there was seasonal variation. During the reproductive period the percentage of males in the population decreased significantly, while after reproduction and during recruitment they increased. The females in each age class were larger than the males (40.33 mm and 36.72 mean total length for females and males, respectively). The survival rate of females was greater than males (0.73 for females and 0.60 for males). The strategy of this species is to invest in female individuals.     

Analysis of the trophy sport fishery for the speckled peacock bass in the Rio Negro River, Brazil

Abstract  The middle portion of the Rio Negro River in Brazil near the equator supports a popular recreational sport fishery for speckled peacock bass, Cichla temensis (Humboldt). The objective of this study was to determine the effect of fishing mortality on this population. Fish were collected from sport-fishing ( n  = 72) and commercial ( n  = 103) catches and otoliths were aged to estimate longevity, growth and natural mortality. Recreational anglers in this region seek to catch, then release, larger speckled peacock bass; and fish larger than 62 cm standard length (SL) (about 4.5 kg) served as a bench mark to assess the potential impact of subsistence and commercial harvest on the abundance of larger fish in the sport fishery. Time of opaque band formation on otoliths generally coincided with the dry season (November to April); these bands appeared to form once per year, but formation was highly variable. Speckled peacock bass grew to 62 cm SL on average in 6.4 years, but some fish obtained this size in 4–5 years. Maximum age was 9 years, but most fish were less than 7 years. Instantaneous annual natural mortality ( M ) estimated from maximum size, longevity and growth ranged from 0.19 to 0.44. Simulation modelling predicted that exploitation rates of fish >25 cm SL similar to the estimated natural mortality rates would reduce the abundance of fish >62 cm by 67–89% compared with no harvest. Even modest exploitation rates of 5% and 10% would result in approximately 30–50% reduction, respectively, of these larger fish. Abundance of large speckled peacock bass that sustains the sport fishery is susceptible to low rates of exploitation in this remote region of Brazil.     

Age and growth of the silky shark Carcharhinus falciformis from the Pacific Ocean

ABSTRACT:   The present study estimated the age and growth of the silky shark Carcharhinus falciformis in the Pacific Ocean. Samples and biological data were collected from Japanese tuna longline and purse seine fisheries from 1992 to 1999. Vertebra centra were picked from 145 males and 153 females for age determination. The number of annual rings observed for males and females was 0–8 and 0–13, respectively. Combined sex von Bertalanffy growth equations were obtained as follows: L_t  = 216.4(1 − e^{−0.148( t +1.76)}) where L_t is precaudal length in cm at age t . A mature size for males was considered to be approximately 135–140 cm (precaudal length), with an estimated age of 5–6 years, whereas corresponding values for females were 145–150 cm and 6–7 years, respectively. Birth size ranged from 48 to 60 cm. There was no remarkable difference in growth, birth size and age at maturity between the Pacific and Atlantic Oceans. The life history parameters of the silky shark are approximately the same in both oceans.     

Estimate of reproductive value of the big eye Priacanthus macracanthus in the north-eastern waters off Taiwan

ABSTRACT: The reproductive value and population status of the big eye in the north-eastern Taiwan waters was estimated by demographic analysis using available life-history parameters. Life-history tables were constructed using estimates of natural mortality ( M ) of 10.4920/year for age 0 and 0.3256/year for ages 1–9, with a maximum age of 9. Age-specific batch fecundity ( F_e ) was from F_e  = 1391.34e^{0.1782 FL} . The age-specific proportion of maturity was estimated from the relationship between the proportion of female maturity ( Pr ) and fork length ( FL ): Pr  = 1/(1 + e^{15.081−0.796 FL} ). Females mature at age 3 and mature females reproduce every year. The population increase rate (λ) was estimated to be 20.5% per year and the generation time ( G ) was 6.25 years without exploitation. The net reproductive value ( R₀ ), generation time and intrinsic rate of natural increase ( r ) decreased with increased fishing mortality. For fixed fishing mortality, when F  = 1.2/year and fishing started at age 3, R₀ was estimated to be 1.0 and the population was considered to be in equilibrium. For age-specific fishing mortality, when fishing started at age 3, R₀ was estimated to be 0.96/year, G being 6.18 years, and the population decreased 0.7% per year. The big eye population had a strong resilience as long as F  < = 1.3/year started at an age that was older than the age at maturity (i.e. 3 years old) but would decline when intensive fishing ( F  > = 1.2/year) started at age 2 or younger. Sensitivity analysis indicated that the mortality of age 0 is the most sensitive parameter in demographic analysis.     

Laboratory-based reproduction success of ruffe, Gymnocephalus cernuus (L.), in brackish water is determined by maternal properties

Abstract – Body length, age, egg size, embryo salinity tolerance and length at hatching of the freshwater (salinity <0.1 ppt, Lake Peipsi) and brackish-water (salinity 2–6 ppt, Pärnu and Matsalu Bay) ruffe, Gymnocephalus cernuus (L.), were examined to reveal their reproductive success in moderate salinity. Eggs of females originating from brackish water were significantly larger than eggs of freshwater females. No correlation between egg size and female size and age was found in brackish-water populations. In the freshwater population there was a small negative correlation between egg size and female size, but no correlation with female age. Fertilisation by sperm of males of different origin (brackish water or freshwater) produced no significant differences at any critical developmental stage (fertilisation, gastrulation, hatching) in the development of eggs from brackish-water or freshwater females at 3.3, 5.5, 7.7 and 9.9 ppt salinity. Survival rates in different salinity depended only on female origin; embryonic salinity tolerance was higher in ruffe inhabiting brackish water. Obviously, embryo salinity tolerance in ruffe is determined by egg qualities.     

Stimulatory effect of thyroid hormones improves larval development and reproductive performance in alligator gar (Atractosteus spatula) and spotted gar (Lepisosteus oculatus)

Development of alligator gar (Atractosteus spatula) and spotted gar (Lepisosteus oculatus) larvae was evaluated after exposure of embryos to thyroid hormones (TH) by two different methods of administration. For the first method, alligator gar embryos were placed in a water bath with triiodothyronine (T₃; 1 ppm for 2 h), and control treatment embryos were placed in a water bath without T₃. For the second method, spotted gar adult males and females were injected with different TH during induced spawning: a group was injected with T₃ [20 mg kg^?1 body weight (BW)], a second group with thyroxine (T₄; 20 mg kg^?1 BW), a third group with thyroid‐stimulating hormone (TSH; 4 IU kg^?1BW) and a control group with dimethyl sulfoxide. Both methods resulted in increases in the concentrations of T₃ and T₄ in embryos of both species. An increase in the alkaline enzymatic activity of TH‐treated larvae was observed as well as an increase in the RNA:DNA, RNA:Dry weight and DNA:Dry weight ratios at hatching. Some positive effects of TH application were: a significant increase in the hatching rate of spotted gar larvae from TH‐injected parents and a higher percentage of successful spawns. Evenness of larval sizes and a higher survival rate were observed in alligator gar larvae. Snout development was accelerated by TH treatment in both species.     

Coral communities of Biscayne Bay,Florida and adjacent offshore areas: diversity,abundance, distribution,and environmental correlates

• 1. Hardbottom habitats of Biscayne Bay, a shallow lagoon adjacent to the city of Miami, Florida, USA, contain a limited number of coral species that represent a small subset of the species found at nearby offshore hardbottom and reef habitats of the Florida Reef Tract. Although the physical characteristics of this basin make it a marginal environment for coral growth, the presence of dense populations of Siderastrea radians and Porites furcata indicate that these, as well as other corals that are found at lower densities, are able to tolerate extreme and fluctuating conditions. Three factors, temperature, sedimentation, and salinity, appear to limit coral abundance, diversity, and distribution within Biscayne Bay.
• 2. Temperatures exhibit high frequencies of extreme high and low values known to cause coral stress and mortality elsewhere. Similarly, sedimentation rates are very high and sediment resuspension caused by currents, storms and boating activities commonly bury corals under sediment layers. Sediment burial was shown experimentally to influence growth and mortality of S. radians.
• 3. The salinity of Biscayne Bay is influenced by freshwater inputs from canal, sheetflow and groundwater sources that create a near‐shore environment with low mean salinity and high salinity fluctuation. Coral communities along this western margin have the lowest coral density and species richness. Chronic exposure to low salinity was shown experimentally to cause a decrease in the growth of S. radians.
• 4. The location of Biscayne Bay, downstream of a large restoration effort planned for the Everglades watershed, highlights the need to understand the relationship between the physical environment and the health of benthic communities. The data presented here provide the type of scientific information needed so that management decisions can take into account the potential impacts of human activities on the health of coral populations that are already near their tolerance limits for temperature, salinity, and sedimentation.

Copyright © 2003 John Wiley & Sons, Ltd.     

Dependence of recruitment on parent stock of the spiny lobster,Panulirus argus,in Florida

Despite management practices to achieve sustainability, commercial landings for Florida spiny lobster (Panulirus argus) have experienced a drastic decline (57%) since 2000. This is cause for concern not only for economic reasons, but for issues of sustainability. An annual index of P. argus post‐larval (puerulus) abundance, estimated with a generalized linear model with significant mean sea‐level effects, shows a 36% decrease in annual puerulus supply since 1988. In addition, local Florida spawning stock biomass estimated from an age‐structured sequential population analysis decreased 57% since 1988. Puerulus abundance follows a highly correlated (R = 0.76) trend with a 12‐month delayed spawning stock abundance, which supports the contention that the Florida spawning population is a significant contributing factor to post‐larval recruitment in Florida. Residuals about the puerulus on spawning stock abundance function follow closely an interannual North Atlantic Oscillation Index signal. This residual effect is thought of as a secondary regional population effect on Florida puerulus recruitment. The Florida spiny lobster stock is exploited with no fishing mortality controls due to the Pan Caribbean recruitment concept adopted in Florida spiny lobster management. Therefore, the potential of recruitment overfishing exists if fishing mortality controls to protect local spawning stock abundance, such as catch quotas, are not introduced.     

Sexual dimorphism in growth and maturation of turbot, Scophthalmus maximus (Rafinesque, 1810)

Sexual dimorphism in growth and maturation of individually tagged turbot (n= 421), Scophthalmus maximus Rafinesque, was studied in a long-lasting (20 months) growth experiment with four temperature regimes. The influence of onset of puberty and subsequent maturation on growth was evaluated. There were no initial size differences, but the final weight of females was larger than that of males at all temperature regimes, except at the lowest temperature. Surplus energy (sum of increase in somatic weight and gonad weight) in females was on average greater than in males from 8 months prior to first spawning. Significant growth (as specific growth rate, SGR) differences between maturing and immature fish were detected from the age of 9 months post hatch. Maturing females had the highest growth rate and reached the largest size (1.8 kg in 20 months), whereas male body weights reached a plateau and levelled off around 1.0 kg. To optimize production characteristics in turbot aquaculture and achieve more homogeneous growth, methods should be developed to produce all-female broods.     

Cholesterolaemia and triacylglycerolaemia in farmed rainbow trout,Oncorhynchus mykiss

Physiological (reference) value intervals determined by the lower 2.5% and upper 97.5% quantiles were calculated for blood plasma cholesterol (CHOL) and triacylglycerol (TGL) in farmed rainbow trout, Oncorhynchus mykiss, in raceway culture. The fish were given dry pelleted diets that contained 37–47% crude protein and 7–14% crude fat and were kept at a stocking density of 50 kg m^?3 in tanks provided with running freshwater at an ambient temperature of 3–16°C and dissolved oxygen, 8.4–11.5 mg L^?1. Blood was sampled between September and November at a photoperiod of 9:00–13:00 hours: 11:00–15:00 hours (light:dark). Cholesterol levels were significantly (P = 0.0001) greater in males (4.7–12.1 mmol L^?1, n = 34, mean weight 406 ± 138 g) than immature females (3.2–9.7 mmol L^?1, n = 386, mean weight 416 ± 147 g). Physiological range for TGL in immature females and males was 2.4–14.4 mmol L^?1 (n = 249, mean weight 418 ± 149 g). The distribution and density of the quantiles in the tested reference group were made possible by the use of histograms, which showed normal distributions for CHOL in males and in females, but not for TGL, in which a sinistral asymmetry was found. Correlation and regression analyses indicated significant (P = 0.0000) dependence between the CHOL and total protein (r² = 76.2%), CHOL and Fulton's condition factor (r² = 43.3%) and CHOL and absolute weight of liver (r² = 45.5%). Fluctuation in cholesterolaemia and triacylglycerolaemia, depending on nutrition and the aquaculture method is discussed below.     

Induction of sex inversion in common snook (Centropomus undecimalis) males,using 17‐β oestradiol implants

The common snook (Centropomus undecimalis) is a protandric hermaphrodite fish that has potential for aquaculture due to its high value and market acceptance. One of the difficulties to its reproduction in captivity is that females are older and bigger than males. The objective of this study was to use 17‐β oestradiol (E2) hormone implants to induce sex inversion in adult males. Fish with an initial body weight of 383 ± 83 g (mean ± SD), individually tagged were used in the experiment. Four E2 dosages (n = 7) were tested (0.5, 1.0, 4.0 and 8.0 mg   kg^?1) in Ethylene‐vinyl‐acetate (EVAc) implants, and a control group (n = 7) implanted without hormone. The parameters evaluated were: survival, weight gain, hepatosomatic and gonadosomatic indices (GSI and HSI) and plasma levels of testosterone (T) and 17‐β oestradiol (E2). Also, liver and gonad morphology was observed through histological sections. GSI was higher in E2 treated than in control fish. All E2 treated fish had completely developed ovaries with oocytes at the perinucleolar stage, while all fish in the control group remained males with evidence of active spermatogenesis. After 15 days, plasma levels of E2 were correlated with the hormone dosage. T levels in the control group were higher than in E2 treated fish, at all sampling times. In conclusion, 0.5 mg   kg^?1 of E2 in EVAc implants is effective to induce sexual inversion in common snook males, which could be useful to obtain broodstock females smaller than in the wild in a reduced time.     

Reproductive biology of common silver biddy Gerres oyena in Okinawa Island of southern Japan

ABSTRACT:   Common silver biddy Gerres oyena were collected monthly between November 2002 and November 2005 in Okinawa Island of southern Japan. The seasonal reproductive cycle of this species was investigated using the gonadosomatic index (GSI) and through histological observation of gonads. Temporal variation in the GSI reflected gonadal development from histological observations; ovary development occurred from March to September and testes development occurred between March and August. Maximal development was observed in April and May in both sexes. While mean values for hepatosomatic and lipidosomatic indices decreased markedly in females relative to males during gonadal development, mean condition factors decreased with gonadal recrudescence in both sexes. The minimum standard length (SL) at sexual maturity was 89.7 mm for females and 81.4 mm for males and the size at which 50% of individuals were sexually mature was 104 and 92 mm SL in females and males, respectively. The power relationships of batch fecundity (BF) versus standard length (SL, mm) and body weight (BW, g) of females can be expressed as BF  = 46.7 × e^{1.64 SL} and BF  = 19 697 × e^{0.49 BW} , respectively.