Seasonal Von Bertalanffy Growth Research Articles

Information on the deep-water giant red shrimp Aristaeomorpha foliacea (Risso, 1827) (Crustacea, Decapoda, Aristeidae) population in Antalya Bay (Eastern Mediterranean Sea, South of Turkey) based on the MEDITS protocol

The main aim of this study was to contribute to the current knowledge on the population of Aristaeomorpha foliacea in Antalya Bay located on the southern coast of Turkey in the Mediterranean Sea. Monthly samples were collected between July 2016 and July 2017 from experimental trawl surveys in accordance with the International Bottom Trawl Survey in the Mediterranean (MEDITS) protocol. The abundance index was calculated as 4308.6 N/km 2 and the biomass index as 66.8 kg/km 2. The relationship between total weight (TW) and carapace length (CL) was estimated to be TW = 0.00078⋅CL2.76 for females and TW=0.00049⋅CL2.92 for males. The seasonalized von Bertalanffy growth parameter estimates were CL∞=66.12mm, K=0.43 years −1, tanchor=0.36 years, C=0.63 and ts=0.21 years for females, and CL∞=44.02mmK=0.39 year −1, tanchor=0.30 years, C=0.77 and ts=0.87 years for males. Female shrimps grew slightly faster and reached a larger asymptotic size hence exhibiting a greater growth performance than males. The spawning season was determined as the summer. Recruitment took place in spring, and the sex ratios were found to be 1.29:1 in favor of males. The median size at first maturity was estimated as 37.7 mm CL for females and 30.1 mm CL for males. The annual total mortality rate was 1.66 and 1.41, the annual natural mortality rate 0.57 and 0.72, and the exploitation rate 0.66 and 0.49 for females and males, respectively. The fishing ground for A. foliacea in Antalya Bay is situated within 12 nautical miles off the shore within the territorial waters, thus closed to commercial trawl fisheries between 15 April and 15 September in accordance with the Turkish fishery regulations. The closing period, which coincides with the spawning season and also provides a reduction in the fishing pressure, is clearly of great importance for the sustainability of this species in Antalya Bay.

Estimating growth from length frequency distribution: comparison of ELEFAN and Bayesian approaches for red endeavour prawns (Metapenaeus ensis)

Abstract Using length frequency distribution data (LFD) is cost-effective for estimating somatic growth in fish or invertebrates as length data are relatively easy to obtain. The recently developed R packages TropFishR and fishboot extend classic ELEFAN (Electronic LEngth Frequency ANalysis) programs and include more powerful optimization procedures and a bootstrap method for estimating uncertainties. Yet, the fundamental functions require users to provide search conditions (e.g. upper and lower limits for each parameter, length-class size, number of length-classes for the calculation of moving average), which can significantly affect the results. In this paper, we compare the ELEFAN approach with a Bayesian approach in analysing LFD, employing both standard and seasonal von Bertalanffy growth functions. We apply both approaches to a commercially valuable but poorly studied red endeavour prawn (Metapenaeus ensis) harvested in Australia's Northern Prawn Fishery. Sensitivity tests on ELEFAN confirm that any change in search settings would affect the results. Simulation studies on Bayesian growth models show that Linf and K can be accurately obtained even with modal progression of only one year-class and using non-informative priors. However, age information, including the theoretical age at length zero (t0), is difficult to estimate and requires LFD from multiple age classes and informative priors. The Bayesian models yield mean parameters of: Linf = 36.56 mm (carapace length), K = 2.74 yr–1, and t0 = -0.02 yr for the males, and Linf = 51.81 mm, K = 1.94 yr–1, and t0 = -0.02 yr for the females. Seasonal oscillation models fit the LFD better, but the improvement is small and the estimated season-related parameters have large variances.

Otolith Weight as an Estimator of the Age of Seriola lalandi Valenciennes, 1833 (Carangidae), in the Southeastern Pacific.

Simple SummaryThe healthy management of fishery resources requires the evaluation of a series of population attributes, such as mortality, fecundity, spawning biomass, recruitment and the age at which fish reach sexual maturity. All these attributes depend on the age of fish. Then, the adequate administration and management of these resources require estimators of fish age. Age is estimated by ring counts in the otoliths, which are hard and calcified structures responsible for the balance of fish; however, this is an expensive and time-consuming methodology. An alternative is the use of otolith weight due to its expected relationship with fish age. Yellowtail king fish is a valuable resource, which arrives at the Chilean northern coast in the summer (southern hemisphere). Many aspects of the biology of this fish, such as age and growth, remain unknown. In this study, we estimated the age and growth using otolith weight, which was measured from fish with a known age, and we calculated parameters explaining growth using four different models. The best model was the seasonalized von Bertalanffy growth function, which takes into account that fish do not grow at the same rate year round.The age and growth of fish populations is a critical issue for stock assessment, population dynamics and fishery management. Spawner biomass, mortality, growth, recruitment and age at maturity can be misconstrued if the age estimator is inaccurate. Age can be estimated by annuli count, but this requires expertise and is expensive. Otolith weight (OW) is a good indicator of how long a fish has lived, because OW increases during an individual’s life. Seriola lalandi is a migratory fish and is an important resource for local fishermen in northern Chile. Aspects of its biology, i.e., age and growth, remain unknown, at least for the population annually arriving in northern Chile. Fish of a known age (n = 105; from 5.5 to 25.7 cm in FL) from yellowtail aquaculture facilities at Universidad de Antofagasta allowed us to estimate the growth rate of OW, and fish obtained from local fishermen (n = 71; from 37.9 to 109 cm in FL) allowed us to estimate the age and growth of S. lalandi from the analysis of OW, without the need for calibration. The following four models were fitted with the known ages and fork lengths: the von Bertalanffy growth function, the Gompertz and logistic models and the seasonalized von Bertalanffy growth function. The latter model showed the best adjustment (according to the Akaike information criterion) with the following parameters: L∞, 98.58 cm.; K, 0.59; t0, 0.07; ts, 0.84; and C, 0.97.

Comparison of Electronic Length Frequency Analysis (ELEFAN) for Estimation of Growth Parameters for Lollyfish, Holothuria (Holothuria) atra and Sand Sea Cucumber, Holothuria (Thymiosycia) arenicola (Holothuroidea: Echinodermata) in the North Arabian Sea, Pakistan

To estimate the growth parameters, the non-seasonal von Bertalanffy and Hoenig seasonal von Bertalanffy models were fitted to the length frequency data of Holothuria atra and H. arenicola obtained from coastal areas of Karachi in the northern Arabian Sea, Pakistan between January and December 2014. The Hoenig seasonal von Bertalanffy growth parameters were estimated as L∞=36.1 cm total length (TL), K=0.75 year-1 for H. atra and as L∞=34.9 cm TL, K=0.70 year-1 for H. arenicola. H. atra individuals reached 73.9% of their maximum total length at the one year old. For H. arenicola it was calculated as 72.7%. Monthly mean growth rate of H. atra at the same ages was calculated higher than H. arenicola. The seasonal oscillation in growth rate for H. atra (C=0.50) was larger than it was for H. arenicola (C=0.37). The time of the year when the growth is slowest corresponded to the middle of April (WP=0.30) in H. atra and at the beginning of August (WP=0.60) in H. arenicola may be the result of the extended both reproduction and poor nutrition periods due to monsoonal effects on the marine environment. The relatively high growth rates (K>0.7 year-1) of these two species may have important implications for high survival rate, particularly in environmental condition where cause biological stress and marine confusion but may also increase their potential as a candidate species for aquaculture.

Reproduction and Seasonal Growth Estimates of the Black Goby, Gobius niger (Osteichthyes: Perciformes: Gobiidae) in the Southeastern Black Sea Region of Turkey

Seasonal growth pattern and reproductive biology of the black goby, Gobius niger, were studied in southern Black Sea between December 2012 and November 2013. The seasonal von Bertalanffy growth parameters, computed from ELEFAN, were estimated as L∞ = 11.90 cm TL, K = 0.701 year-1, C = 0.633, and WP = 0.492 for the Hoenig seasonal model and as L∞ = 12.14 cm TL, K = 0.680 year-1 for non-seasonal von Bertalanffy model. The size at sexual maturity (TL50) was estimated as 8.9 cm TL. The GSI ranged 0.60 in December and 8.57 in April (mean 3.82±0.818) for females and between 0.61 in October 2013 and 2.90 in May 2013 (mean 1.70±0.260) for males. The seasonal growth was pronounced probably due to reproduction activity which extended investment of energy in reproduction causing slower growth. The GSI development was related to photoperiod and the monthly variations of GSI values indicating that the intensive spawning occurred between April and August. During spawning time, the mean GSI value of females (6.04±1.177) was 2.9 times higher than the mean GSI values of males (2.08±0.423) (P < 0.05). The results of this study were offered as biological input parameters regarded as a reference for the conservation and management of the Black Sea stocks of the black goby.

Length based growth estimation of sea cucumbers (Holothuria verrucosa and Holothuria pardalis) (Holothuroidea:Echinodermata) collected from coastal areas of Karachi, Pakistan (northern Arabian sea)

To estimate the growth parameters, the non-seasonal von Bertalanffy and Hoenig seasonal von Bertalanffy models were fitted to the length frequency data of Holothuria pardalis and H. verucosa obtained from coastal areas of Karachi during January and December 2018. The Hoenig seasonal von Bertalanffy growth parameters were estimated as L∞ = 18.0 cm total length (TL), K = 1. 00 year-1 for H. pardalis and as L∞ = 18.0 cm TL, K = 0.86 year-1 for H. verrucosa. H. verrucosa individuals reached 68.9% of their maximum total length at the one year old class. For H. pardalis it was calculated as 54.2%. The seasonal oscillation in growth rate for H. pardalis (C = 0.90) was larger than it was for H. verrucosa (C = 0.18). The slowest period of growth corresponded to June in H. verrucosa and February in H. pardalis may be the result of the extended both reproduction and poor nutrition periods due to high rainfall regime. The relatively high growth rate (K) of these species may have important implications for their survival, mainly in environments where conditions cause biological stress and oceanic disturbances but may also increase its potential as a candidate for aquaculture.

Reproduction, Growth, Mortality and Yield of the Goatfish Upeneus sulphureus in Northern Bay of Bengal, Bangladesh

Information on stock condition and reproductive biology are important for fisheries conservation and management planning. This study examined reproduction, growth, mortality and yield of sulphur goatfish (Upeneus sulphureus Cuvier 1829), which is a low-value food fish abundantly caught as bycatch in artisanal and industrial fishing from the southeast coast of Bangladesh at northern Bay of Bengal. Data were collected monthly obtaining samples from local fish landing center. The gonadosomatic index indicated that U. sulphureus spawns twice a year during January–May and August–October. Fecundity of the fish was positively correlated with the body and gonad weight, and varied from 15 128–97 274 eggs with fish weight 11.30–58.73 g. Monthly length–frequency distribution was analyzed through FISAT software, thus the estimated seasonalized von Bertalanffy growth parameters were L∞ = 21.80 cm, K = 0.54 per year, C = 0.5, WP = 0.1 and Rn = 0.300, respectively. Moreover, the value of seasonalized total mortality coefficient Z (2.24) was smaller than that of the non-seasonalized Z (4.16). The instantaneous natural mortality and fishing mortality, calculated for non-seasonalized total mortality, were 1.31 and 2.86, respectively. Furthermore, the high exploitation rate (E = 0.69) was close to maximum exploitation level (Emax = 0.75) in yield-per-recruit analysis, suggesting that U. sulphureus is being exploited at the MSY (maximum sustainable yield) level. Therefore, further increase in fishing effort may reduce U. sulphureus stocks in the coastal waters of Bangladesh.

Age, Growth and Mortality of Unio tigridis (Bourguignat, 1852)

Unio tigridis has an importance for the biodiversity of freshwater ecosystem of the Turkey. However, there is no available literature in the world on the growth of this species yet. The aim of this study, therefore, was to describe the age, growth and mortality of this species living in Lake Gölbaşı from Hatay providence, Turkey. A total 428 of specimen were collected using by divers with hand dredges in depth of 1 to 6 meters based on annual sampling strategy from June- 2004 to May- 2005. Lengths and weighs of sample were ranged as 2.1 to 9.2 cm (6.79 ± 1.52) and 1.1 to 73.05 g (34.18 ± 15.56), respectively. Weight-Length relationship of all specimens was described as W=0.193L2.63 (R2=0.94). Thus, a negative allometric growth was detected in the sampled population. The age of each individual was determined by counting the external shall annuli-growth interruption lines. The sampled population was composed of 18 age classes. Specimen belong to age class 7 was the most presented with 20.33 percent in the population. The rate of male to female (m:f) was 0.91:1. Seasonalized von Bertalanffy growth model (SVBGM) was used to describe the growth. From these results, it was shown that seasonality in growth does not occur in this lake for this species (L∞ = 8.80 cm (Shell Length), K = 0.271 year-1, t0 = -0.161 year, C = 0.014, ts = 0.100 year with RSS = 23.22). The total mortality rate (Z ± Se) was calculated as 0.401 ± 0.015 year-1 with R-square = 0.99 (CL of Z with 95 % = 0.361 - 0.440 year-1). Although, there is no fishing, no pollution and no predation risk on this species yet, due to growth characteristic, high K and low L∞, this type of species are vulnerable to extinction.

Population dynamics and secondary production of the ghost shrimp Callichirus major (Thalassinidea): A keystone species of Western Atlantic dissipative beaches

We describe the autoecology of the thalassinid crustacean Callichirus major, a dominant macrofaunal species, on a relatively non-impacted Brazilian dissipative beach. At Rasa Beach (22°45’S, 41°56’W, southwestern Atlantic), monthly sampling was carried out during spring low tides at two sites, 1.3 km apart. Seasonal von Bertalanffy growth curves were adjusted by the ELEFAN routine (FiSAT-II) for the entire population and for each gender separately. Considerable differences in density, biomass, secondary production and size composition of C. major from the two sites indicate that it is not possible to extrapolate our results to the entire beach since there are significant heterogeneities between the two sampling sites. The higher secondary production at one of the sites may be caused by its higher populational density, associated with the occurrence of a higher proportion of juveniles. The renewal rate of the local population of C. major (P/B ratio from 0.85 to 2.19) is smaller than for other beach macrocrustaceans studied in different localities worldwide.

Population dynamics of Philocheras trispinosus (Crangonidae) with abundance of other caridean shrimps (Crustacea: Decapoda) caught by beam trawl in the Southern Black Sea, Turkey

Objective: To determine growth and reproduction biology of Philocheras trispinosus (P. trispinosus) with abundance of other caridean shrimps caught by beam trawl in the Southern Black Sea. Methods: Samplings were carried out monthly with a beam trawl of 2 m length and 15 mm cod-end mesh size between December 2012 and November 2013. All individuals were sampled between 1 and 40+ m water depth from 146 hauls. Results: A total of 550 P. trispinosus, 618 Palaemon adspersus, 12 Palaemon serratus, 11 Philocheras fasciatus and 10 Crangon crangon were sampled during the study period. The crangonid shrimps started appearing during the winter and spring and the number of individuals increased to reach their highest value in mid-winter and mid-spring. The seasonal von Bertalanffy growth parameters for P. trispinosus were estimated as L∞ = 29.3 mm total length, K = 0.860/year, t0 = –0.900 year, C = 0.180, and ts = 0.010. The start of the slow growth period was at the beginning of July (WP = 0.510). Ovigerous females appeared in the sampling area between January and April. Size at sexual maturity was estimated as 25.69 mm total length. Conclusions: The results supported the distribution and abundance of caridean shrimp species from the study area and the population dynamics of the most abundant shrimp species, P. trispinosus. The current study can be answered as baseline data prior to management strategies to ensure sustainable conservation of the shrimp species.

Age estimation and growth pattern of the grouper Cephalopholis taeniops (Epinephelidae) off the Cape Verde Archipelago, north-west Africa

The grouper Cephalopholis taeniops is a carnivorous fish of the Cape Verde coastal marine ecosystem. Nothing is known regarding the age and growth of this epinephelid. In this study, the age and growth of C. taeniops was investigated by annual growth increment counts from 2804 specimens (7–51 cm total length) collected between January 2005 and December 2011. Whole otoliths underestimated the age indicated in sections by approximately 70%; therefore, sectioned otoliths were used in this study. A year's growth was represented by one opaque and one translucent ring. There was no apparent time lag from the start of the increase in the seawater temperature and the beginning of the formation of the opaque ring. The formation of the translucent rings coincided with a decrease in surface seawater temperature. Cephalopholis taeniops is a slow-growing and long-lived species, with ages of up to 20 years recorded. The seasonalized von Bertalanffy growth function was the best fitted among the four models tested, with an Akaike weight higher than 0.99. Growth was described by the seasonalized von Bertalanffy growth function as follows: L∞ = 54.26 cm, k = 0.135 year−1, t0 = −0.853 year, C = 0.439 and ts = 0.667.

Some population parameters of Ruditapes philippinarum (Bivalvia, Veneridae) on the southern coast of the Marmara Sea, Turkey

Ruditapes philippinarum, a venerid clam, is a dominant species in the sandy and muddy areas in the coastal waters of the Marmara Sea. Intensive commercial harvesting of this species is conducted in these regions. We studied the population dynamics of R. philippinarum on the southern coast of the Marmara Sea (Bandırma). Samples were collected on a monthly basis between September 2012 and August 2013. Seasonal von Bertalanffy growth parameters using the length–frequency distribution of R. philippinarum were estimated at L ∞ = 67.50 mm and K = 0.33 year−1, and the seasonal oscillation in growth rate was 0.53. The slowest growth period was in January. The growth performance index and potential lifespan were 3.182 and 8.06 years, respectively. The growth relationship was confirmed to have a positive allometric pattern. The average total mortality rate was estimated to be 0.777 year−1, whereas the natural and fishing mortality rates were 0.539 and 0.238 year−1, respectively. The current exploitation rate of R. philippinarum was 0.306. The recruitment pattern peaked during June–August, and spawning occurred between May and August. The results of this study provide valuable information on the status of R. philippinarum stocks.

Crecimiento y mortalidad de la madreperla <i>Pinctada mazatlanica</i> en poblaciones naturales del litoral oriental de Baja California Sur, México

The Mexican Pacific mother-of-pearl Pinctada mazatlanica was placed in forbidden fisheries status for the Mexican Federal Government and considered in extinction danger since 1939. This decree was modified in 1994 to allow the capture of spat for research or marine culture. We estimated the growth and mortality of mother-of-pearl from the eastern littoral of South Baja California wild stock in the periods 1992-93 and 1997-99. We used 38 sample stations at 2 bays and 6 insular complexes. The maximum length was 187.22 mm (179.83-195.81 mm, P > 0.95). Seasonal von Bertalanffy growth (ELEFAN I routine) values are: L(infinity) = 193.31 mm, k = 0.54 year(-1), t(0) = -0.1805 year, C = 0.49 and WP = 0.75. The growth performance index was Phi' = 4.305. The total mortality was calculated from a length-converted catch curve Z = 2.03 año(-1). Length-weight relationship W(i) = 0.0005418 * L(i)(2.7301). The growth parameters were similar to those for Pinctada margaritifera var. cumingi (open ocean wild stocks). The wild stock oysters differ from culture individuals at experimental repopulation conditions in Paz Bay. The total mortality is similar to that for Pinctada radiata in the Red Sea.

Population ecology of turbot and brill: What can we learn from two rare flatfish species?

Turbot and brill are widely distributed in the Northeast Atlantic but occur at low abundance. They are ecologically very similar and closely related. The low abundance and the similarities make them particularly interesting to study the population dynamics because it raises the questions how the populations can sustain themselves at low abundances and how turbot and brill avoid strong interspecific competition. Knowledge of both species is hampered by lack of analysed data. The main objective of this study is therefore to increase the knowledge of turbot and brill and in particular to compare the two species in order to address the above questions. Based on biological samples collected in the North Sea, we calculated seasonal von Bertalanffy growth parameters, maturity ogives, monthly gonado-somatic indices (GSI) and condition factors (Fulton's K) and indices of inter- and intraspecific mean crowding and compared the results for turbot and brill. The main differences between the two species were found in their spawning period, with brill having a more protracted spawning period. Brill also showed an earlier peak in their GSI values, suggesting an earlier start of their spawning period. The mean crowding showed that interspecific competition was lower than intraspecific competition. The exploitation pattern was also studied. Turbot and brill are exploited as a bycatch species in the mixed demersal fishery. We found that productivity is highest in areas where the maximum temperature is close to the optimal temperature for growth (16–18°C) and landings decrease where salinity falls below ~5psu (turbot) and ~15psu (brill). Recent fishing mortality rates of North Sea turbot are around 0.5–0.7, but there is no indication that recruitment is impaired at low levels of spawning stock biomass. We conclude that although both species have similar ecological characteristics, differences may reduce inter-specific competition.

Population dynamics of Niger River prawn (Macrobrachium felicinum) in Lower Taylor Creek, Niger Delta, Nigeria

The population dynamics of Macrobrachium felicinum (Holthuis, 1949) in Lower Taylor Creek, Niger Delta, Nigeria, was analysed using monthly length-frequency data (June 2008 – May 2010). This study was aimed at determining the status of fishery and establishing the levels of exploitation that will give sustainable yields. The FAO-ICLARM stock assessment tool (FISAT II) software was used to estimate population parameters. The growth parameters obtained from the seasonalised Von Bertalanffy growth function were L∞ = 10.24 cm total length, K/year = 1.40, C = 0.85; and WP = 0.79 (September). Using a length-converted catch curve, total mortality (Z) was estimated at 9.50/year, natural mortality (M) at 3.04/year, while fishing mortality (F) was estimated at 6.46/year. From the probability of capture estimation, the length-at-first capture (Lc ) for M. felicinum was 4.55 cm. One major recruitment peak per year was established for M. felicinum, while the relative yield-per-recruit analysis predicted the maximum ex...

Sexual seasonal growth of the European anchovy (Engraulis encrasicolus) caught by mid-water trawl and purse seine in the southern Black Sea

The seasonal growth pattern and size composition of the European anchovy, Engraulis encrasicolus caught by mid-water trawl and purse seine was studied in the southern Black Sea between October 2010 and April 2011. Total length (TL) and size distribution of females caught by purse seine was higher than males and females obtained from mid-water trawl (P < 0.05). The seasonal von Bertalanffy growth parameters, computed from monthly length–frequency distributions, were estimated as asymptotic length to which the fish grow (L∞) = 13.01 cm TL, growth-rate parameter (K) = 0.993 year−1, amplitude of the sinusoidal growth oscillations (C) = 0.800, and the time of the year when the growth rate is slowest, the winter period (WP) = 0.298 for males and as L∞ = 13.69 cm TL, K = 1.249 year−1, C = 0.950, and WP = 0.151 for females caught by mid-water trawl. The seasonal von Bertalanffy growth parameters for anchovy obtained from purse seine fishing in the Rize region were estimated as L∞ = 14.00 cm TL, K = 0.800 year−1, C = 0.980, and WP = 0.212 for males and as L∞ = 13.93 cm TL, K = 0.994 year−1, C = 0.725, and WP = 0.319 for females. The period of slowest growth for males and females estimated between February and April, which is the period with a relatively low water temperature and consequently anchovy in the southern Black Sea have a seasonal growth pattern.

Population dynamics of the amphioxusBranchiostoma elongatumfrom northern Chile

Amphioxi represent the evolutionary link between vertebrates and invertebrates. For this reason, research dealing with these animals has been focused mainly on embryological and anatomical studies. Out of 30 described species, only one,Branchiostoma elongatum, is known to inhabit shallow sandy bottoms along the Humboldt Current System (HCS) of Chile and Peru. The population dynamics ofB. elongatumfrom northern Chile was studied between February 2008 and January 2009, and the results were compared with other species within the genusBranchiostomainhabiting distinct ecosystems. Mean abundance ofB. elongatumwas low (158.6 ind m−2) in comparison with the abundance of other species withinBranchiostoma. Although the gametogenic activity was continuous, a clear spawning event was observed between August and October, which seemingly produced a recruitment pulse during the summer and consequently a simultaneous increase in population density and decrease of mean length during that period. Growth ofB. elongatumwas best fitted to the seasonalized von Bertalanffy growth function (K = 0.45 year−1and L∞= 64.6 mm), with faster growth during summer–autumn. Growth performance (Ф′ = 3.273) was high in comparison with other species within the genus. Mortality ofB. elongatum(Z = 1.075 year−1) was well fitted to the single exponential model (r2= 0.92). The annual total production ofB. elongatumreached 0.68 g ash-free dry mass (AFDM) m−2and the annual mean biomass was 0.56 g AFDM m−2, which determined a production to biomass ratio of 1.22. The huge productivity of the HCS was not reflected in a high abundance and biomass ofB. elongatum. However, this species displayed a high growth efficiency and P/B ratio that are comparable to those of otherBranchiostomainhabiting highly productive ecosystems.

Validation of age determination methods and growth studies of the sand sole Pegusa lascaris (Soleidae) from the eastern-central Atlantic

The age and growth of the sand sole Pegusa lascaris from the Canarian Archipelago were studied from 2107 fish collected between January 2005 and December 2007. To find an appropriate method for age determination, sagittal otoliths were observed by surface-reading and frontal section and the results were compared. The two methods did not differ significantly in estimated age but the surface-reading method is superior in terms of cost and time efficiency. The sand sole has a moderate life span, with ages up to 10 years recorded. Individuals grow quickly in their first two years, attaining approximately 48% of their maximum standard length; after the second year, their growth rate drops rapidly as energy is diverted to reproduction. Males and females show dimorphism in growth, with females reaching a slightly greater length and age than males. Von Bertalanffy, seasonalized von Bertalanfy, Gompertz, and Schnute growth models were fitted to length-at-age data. Akaike weights for the seasonalized von Bertalanffy growth model indicated that the probability of choosing the correct model from the group of models used was >0.999 for males and females. The seasonalized von Bertalanffy growth parameters estimated were: L∞ = 309 mm standard length, k = 0.166 yr–1, t0 = –1.88 yr, C = 0.347, and ts = 0.578 for males; and L∞ = 318 mm standard length, k = 0.164 yr–1, t0 = –1.653 yr, C = 0.820, and ts = 0.691 for females. Fish standard length and otolith radius are closely correlated (R2 = 0.902). The relation between standard length and otolith radius is described by a power function (α = 85.11, v = 0.906).

Population dynamics of the Giant African River prawn <i>Macrobrachium vollenhovenii</i> Herklots 1857 (Crustacea, Palaemonidae) in the Cross River Estuary, Nigeria

Growth, mortality, recruitment, yield-per-recruit and present rate of exploitation of the African river prawn Macrobrachium vollenhovenii were studied in the Cross River Estuary, Nigeria. The research was based on length-frequency data collected between January 1997 and June 1998, and FAO-ICLARM Software (FiSAT) routine runs. Growth parameters obtained from the seasonalized von Bertalanffy growth function were L‡ 213.63 and 198.99 mm, K = 1.24/year and 1.24/year; C = 0.95 and 0.95; WP = 0.6 and 0.45, for M. vollenovenii males and females, respectively. Using the seasonalized length-converted catch curves, the instantaneous rate of total mortality Z was estimated as 3.93/year and 6.85/year for males and females. Natural mortality M, fishing mortality F, and exploitation rate E of both sexes were 2.21/year and 2.27/year, 1.72/year and 4.58/year, and 0.44 and 0.67, respectively. The length at first capture Lc estimated from the probability of capture routine was 44.25 mm and 73.41 mm for males and females. One recruitment peak was observed for males, and two of unequal strength for females. Length-weight relationship gave ebf values of 3.483 and 3.329 for males and females, respectively. The relative yield-per-recruit analysis predicted maximum exploitation rates (Emax) of 0.42 and 0.47 as against current exploitation rates of 0.44 and 0.67 for males and females and suggest that only female M. vollenhovenii are being over-exploited. Hence, it is proposed that fishing on females during the reproductive season is reduced, and that the return of egg-bearing females into the waters is enforced.

Age estimation and growth pattern of the island grouper, <em>Mycteroperca fusca</em> (Serranidae) in an island population on the northwest coast of Africa

Mycteroperca fusca es uno de los principales depredadores de los ecosistemas marinos del Archipielago Canario, del que nada se conoce sobre su biologia. En este trabajo, se aborda el estudio de la edad y el crecimiento de M. fusca mediante el recuento de los incrementos anuales de crecimiento a partir de 214 ejemplares recolectados entre enero de 2004 y diciembre de 2005. El crecimiento anual esta representado por un anillo opaco y otro translucido. El abade es una especie perteneciente a la familia Serranidae de crecimiento lento y de vida larga, con edades registradas superiores a los veinte anos. La relacion entre la talla y la edad se estimo mediante el modelo de von Bertalanffy (Loo=898 mm; k=0.062 anos-1; y t0= -3.83 anos), el modelo de Schnute (y1=262 mm; y2=707 mm; a=0.008; y b=1.98), y el modelo estacional de von Bertalanffy (Loo=908 mm; k=0.061 anos-1; t0= -3.83 anos; C=2.58; y ts=0.542). Los machos y las hembras presentaron diferencias en el crecimiento.