Total Length Weight Relationship Research Articles

Comparative analysis of Oreochromis niloticus and a putative hybrid (Wesafu): A Search for morphometric identity

Oreochromis nilotics is an important aquaculture species worldwide. Members of the tilapiine family hybridize easily in nature. The present study was conducted to examine the morphometric and meristic characteristics of Oreochromis niloticus from New Calabar River and a putative hybrid called Wesafu found in Epe Laggon. The study was based on the hypothesis that the tilapia hybrid will possess traits which will be intermediate to those of O. niloticus. A total of 24 morphometric measurements and 8 meristic counts were used to generate data which were analyzed using t-test. The total length of Wesafu and O. niloticus fish ranged from 7.00 -24.5cm and 12.00 -15.5cm respectively. Our study rejected the hypothesis of mid-values Additionally, the total length and body weight relationship were found to be a straight line in logarithmic scale expressed Log BW = 2.7724 Log TL - 1.6171 and Log BW = 2.8442 Log TL - 1.7114 for both Wesafu and O. niloticus respectively. The value of regression co-efficient "b" obtained for the length-weight relationship of Wesafu and O. niloticus was 2.7 and 2.8 respectively.

Spatio-temporal Distribution and Population Dynamics of the Red Mullet Mullus barbatus Linnaeus, 1758 from the South-east Black Sea

A total of 2930 Mullus barbatus individuals collected from the Southeastern Black Sea coast between March 2017 and April 2018 were investigated regarding growth, mortality rates and the distribution determined by depth and season. M. barbatus is abundant along of 30-45 m depth in winter. Total length-weight relationship was determined as W=0.005L3.2344. Von Bertalanffy growth parameters for all individuals were calculated as L∞=28.19 cm, K=0.16 years-1, t0=-0.144 years. The maximum age was 5 years. The total length at 50% maturity was estimated as 11.63 cm in males and 11.68 cm in females. Exponential coefficients of natural mortality, total mortality, and fishing mortality rate of red mullet are estimated as 0.33 year-1, 1.001 year-1 and 0.67 year-1, respectively. The exploitation rate of population was calculated as 0.66 year-1. The fact that exploitation rate is above 0.5 may reflect a high fishing pressure on stock.

Some Population Parameters of Morocco dentex, Dentex maroccanus Valenciennes, 1830 in the Northeastern Mediterranean Sea

In this study, a total of 95 Dentex maroccanus samples (n♀=37, n♂=58) were examined from the northeastern Mediterranean Sea. The sex ratio was calculated as 0.63:1. The mean total length (TL), fork length (FL), and standard length (SL) were 12.1 ± 0.082 cm, 11.1 ± 0.075 cm, and 10.0 ± 0.068 cm for all samples, respectively. The mean weight (W) was 32.81 ± 0.575 g. The length-length relationships were determined as TL=1.1367SL+0.7136, TL=1.0607FL+0.2804, and FL=1.0631SL+0.494 for all samples, respectively. The total length-weight relationships were determined as W=0.08TL2.409, W=0.1183TL2.246, and W=0.0489TL2.613 and the growth was negative allometric for all individuals, females, and males, respectively. The mean condition factor was calculated as 1.84 for all individuals, 1.78 for females, and 1.88 for males. There are no previous studies about the population parameters of Morocco dentex and the present study gave the first information on the length-weight, length-length relationships, and condition factors of D. maroccanus population inhabiting the northeastern Mediterranean Sea

Assessing fishery status and sustainable exploitation of spotted seabass (Dicentrarchus punctatus) in Bardawil Lagoon, Eastern Mediterranean, Egypt

The growth and population parameters of spotted seabass (Dicentrarchus punctatus) in Bardawil Lagoon were investigated to assess their fishery status and propose concrete recommendations for sustainable exploitation. The samples (n = 271) were collected from commercial catches during 2021. As revealed by examining the otoliths, D. punctatus has a short life span of a maximum of four years based on the mean lengths of 20.2, 25.3, 29.7, and 33.5 cm for age groups from I to IV, respectively. The total length-weight relationship equations were W = 0.0120TL2.9672 for males, W = 0.0127TL2.9486 for females and W = 0.0124TL2.9563 for the combined sexes. The von Bertalanffy growth function was Lt = 40.50(1-e-0.38(t+0.66)). The study determined the total and natural mortality rates as 1.58 and 0.79 year−1, respectively, with an exploitation rate (E) of 0.49, which was found close to the optimum value (0.5). However, based on management policies, E was greater than the value corresponding to 50% relative biomass per recruit (E0.5), which indicates that the current fishing effort is unsustainable. Therefore, to maintain the biomass of spawning stocks, the study recommends a 22.4% reduction in the current exploitation rate through the application of fishing regulations that decrease fishing efforts. Such recommendations can help ensure the sustainable exploitation of spotted seabass in Bardawil Lagoon.

Gökçeada (Kuzey Ege Denizi) çevresindeki iki vatoz türünün, Raja miraletus Linnaeus, 1758 ve Dipturus oxyrinchus (Linnaeus, 1758) (Chondrichthyes, Rajidae) beslenme alışkanlıkları

This study investigated the feeding habits of Raja miraletus Linnaeus, 1758 and Dipturus oxyrinchus (Linnaeus, 1758). For the purpose of this study, the specimens were obtained monthly from the commercial trawlers operating around the Gökçeada Island in the Northern Aegean Sea between February 2019 and February 2020. A total of 29 (24 female and 5 male) brown rays (Raja miraletus) and 36 (20 female and 16 male) longnosed skates (Dipturus oxyrinchus) were captured. The total lengths of the R. miraletus specimens ranged between 24.0 cm and 53.9 cm, while the D. oxyrinchus specimens measured between 17.1 cm and 85.0 cm. Total length-weight relationships of R. miraletus and D. oxyrinchus specimens, respectively; W=0.0002TL3.92 (R2=0.97) and W=0.0007TL3.43 (R2=0.97) were calculated. The analysis of the stomach content of the specimens showed that crustacea were the primary and the most important prey group for R. miraletus (IRI% = 67.09), followed by teleosts (IRI% = 1.00) and cephalopods (IRI% = 0.45). The D. oxyrinchus specimens were determined to primarily feed on crustacea (IRI% = 74.3), followed by teleosts (IRI% = 6.50) and nematoda (IRI% = 0.40).

Length-Weight, Length-Length Relationships, and Condition Factor of Red Mullet (Mullus barbatus Linnaeus, 1758) Inhabiting Mersin Bay

This study reports the condition factor, length-weight, and length-length relationships in females, males, and all samples of Mullus barbatus inhabiting Mersin Bay. A total of 152 individuals were sampled. The mean weight (W) was 18.01 ± 0.573 g, and the mean total length (TL), fork length (FL), and standard length (SL) were 12.0 ± 0.094 cm, 11.0 ± 0,086 cm, and 9.9 ± 0.080 cm for all M. barbatus, respectively. The total length-weight relationship was determined as W=0.0033TL3.444 (R2=0.90). The b value was calculated as 3.444 and it showed positive allometric growth for all M. barbatus inhabiting Mersin Bay. The LLRs were calculated as TL=1.0706FL+0.1386 (R2=0.95), TL=1.1634SL+0.371 (R2=0.97), and FL=1.0541SL+0.543 (R2=0.96) for all individuals, respectively. The mean value of the condition factor was calculated as 1.00 ± 0,0093 for all M. barbatus samples. The values of the condition factor in M. barbatus ranged from 0.740 to 1.274. There are few studies about M. barbatus population inhabiting Mersin Bay. In this study, condition factor, length-weight and length-length relationships were determined for M. barbatus inhabiting this region (the northeastern Mediterranean Sea).

Some Biological Characteristics of the Transcaucasian spirlin, Alburnoides fasciatus (Nordmann, 1840) inhabiting Borçka Reservoir, NE Türkiye

The present study investigates for the first time some basic biological aspects such as sex ratio, size composition, length-length relationships (LLRs) and length-weight relationships (LWRs) of Alburnoides fasciatus inhabiting Borçka Dam Lake and its tributaries from the lower Çoruh River Basin located in the northeastern Türkiye. Fish samples were collected from February 2017 to June 2019. Totally 171 specimens ranging from 7.4 cm to 16.2 cm TL and 4.06 g to 46.56 g were sampled. The sex ratio (F:M) was calculated as 1.19:1.00 (χ2 test; P>0.05). The total length-weight relationships were determined as W= 0.008TL3.154 (r2=0.987, N=93) for females, as W= 0.007TL3.183 (r2=0.990, N=78) for males and as W= 0.007TL3.205 (r2=0.981, N=171) for combined sex. The b-values were significantly different from isometric growth (b=3) indicating positive allometric growth of Transcaucasian spirlin for all sexes (Pauly’s t-test; P˂0.05). The regression analysis of LWRs revealed that the coefficient of determination was r2>0.9 showing a highly significant correlation between total length and weight. Results of the LLRs indicated that the values of correlation coefficient were highly correlated (r2>0.9) for each sex and relationship. The differences in b values of the LWR were statistically significant for both sexes (ANCOVA; P

First Data on Some Biological Aspects of the Caucasian Goby, Ponticola constructor (Nordman, 1840) (Teleostei: Gobiidae) From the Lower Çoruh River Basin (NE Türkiye)

The present study describes for the first time some biological aspects (size composition, sex ratio, length-weight relationship and condition factor) of Ponticola constructor (Caucasian goby) inhabiting Borçka Dam Lake and its tributaries from the lower Çoruh River Basin located in the northeastern Türkiye. Fish samples were caught from June 2017 to May 2018 by using trammel nets with various mesh sizes and by pulsed DC electrofishing device. A total of 145 Caucasian goby (78 females and 67 males) ranging from 6.8 cm to 13.4 cm TL were sampled during the study. The sex ratio of female to male was calculated as 1.16:1.00 which did not deviate from the expected ratio of 1:1 (χ² = 0.834, p˃0.05). The total length-weight relationships were determined as W= 0.016TL2.896 (r2=0.995, p˂0.05) for females, as W= 0.018TL2.841 (r2=0.993, p˂0.05) for males and as W= 0.017TL2.856 (r2=0.994, p˂0.05) for combined sex with the b-values were significantly different from isometric growth (b=3) indicating negative allometric growth of Caucasian goby for all sexes (Pauly’s t-test, p˂0.05). The regression analysis revealed that the coefficient of determination was r2>0.99 showing a highly significant correlation between total length and weight. The differences in slopes (b values) of the LWR were statistically significant for both sexes (ANCOVA, p<0.05). Fulton's condition factor (K) values ranged from 1.124 to 1.312 in females and from 1.076 to 1.426 in males indicating a good growth condition in this habitat. No significant difference was observed in mean K values between females and males (t-test, p>0.05). The present study will provide a baseline on some biological parameters of Ponticola constructor to provide a guideline for the fisheries management authority and fisheries scientists for further investigations as well as presents the first known reference on the LWRs of this species for the FishBase database. Furthermore, the reported results may contribute to the conservation and sustainability of this species in the area.

Length-Weight (L-W), Length-Length (L-L) Relationships and Condition Factor of Gobio artvinicus (Teleostei : Gobionidae) from the Lower Çoruh River Basin, NE Türkiye

In this study, some basic biological parameters (e.g. sex ratio, condition factor, LWRs and LLRs) of G. artvinicus (Artvin gudgeon) inhabiting Borçka Reservoir and its tributaries from the lower Çoruh River Basin were investigated for the first time. Fish specimens were collected from June 2017 to May 2018 and totally 120 Artvin gudgeon (65 females and 55 males) ranging from 8.1 cm to 13.2 cm in TL were sampled. The sex ratio (F:M) was calculated as 1.18:1.00 in favour of females, but did not deviate from the expected ratio of 1:1 (χ²=0.834, P˃0.05). The total length-weight relationships were determined as W= 0.008TL3.159 (r2=0.971, P˃0.05) for females, as W= 0.012TL2.971 (r2=0.980, P˂0.05) for males and as W= 0.009TL3.088 (r2=0.970, P˃0.05) for all individuals. While the b-values which reflect the body shape were significantly different from the isometric growth indicating positive allometric growth for females and all individuals (Pauly’s t- test, P˂0.05). however, the b value of males did not differ from the isometric growth (b=3) pattern (Pauly’s t- test, P˂0.05). The slopes (b values) were found statistically significant for both sexes (ANCOVA, P 0.9) for each sex and relationship. Mean Fulton's condition factor values were calculated as 1.128±0.011 for females and 1.102±0.008 for males indicating a good growth condition in this habitat. The present study will provide a baseline on some biological parameters of G. artvinicus to provide a guideline for the fisheries management authority and fisheries scientists for further investigations as well as presents the first known reference on the LWRs and LLRs of this species for the FishBase database. Furthermore, the reported results will contribute to the conservation and sustainability of this species in the area.

SOME ASPECTS OF BIOLOGY OF SNAKE HEAD Channa striatus

Some biological aspects of Channa striatus viz., length-weight relationship, fecundity and condition factor were observed in the laboratory. Sample of 20 individuals of Channa striatus was collected randomly from local market in the Khulna city. The regression equation was found in case of total length and body weight, W = -416.46 + 23.19T (r2=0.896). The arithmetic regression equation of the relationship between the standard length and weight was, W = -382.05 + 26.0371 S (r2=0.908). The regression equation of the relationship between the total length and fecundity was, F = -16046 + 959.671 T (r2=0.859), standard length and fecundity was estimated as F = -14424 + 1070.25 S (r2=0.865) and body weight and fecundity as F = 3965.43 + 32.9612 W (r2=0.764). Among the different linear relationships, total length and body weight relationship was the strongest. Relationship between condition factor and fecundity was the weakest. The fecundity of the species was ranged from 4939 to 22723 and the mean fecundity of the 20 fishes was 14836.050 ± 4019.9612. Maximum fecundity was found in the fish having total length of 38 cm, body weight 475 g and minimum fecundity was found in the fish having total length of 26 cm, body weight 190 g. Condition factor of Channa striatus was found to vary from 0.68167 to 1.35073 with a standard deviation of 0.1748 and the mean value was 0.979 ± 0.1748.

Population dynamics of Pseudophoxinus callensis (Guichenot, 1850) (Cyprinidae) in the National Park of El Kala (Northeast Algeria)

This study concerns the assessment of the morphological parameters, growth and abundance indices oftwo populations of Pseudophoxinuscallensisin Bouhchicha wadi and the Bleu lake within the National Parkof El-Kala (North-East Algeria). According to its environment, P.callensis shows an adaptation throughdifferent strategies. In Bouhchicha wadi, several cohorts coexist all around the year then gradually joinduring the summer season to form pseudo cohorts. In the Blue Lake, P.callensis shows an annual cycle witha single cohort that begins its cycle in April-May then diminishing gradually in late autumn. The FISAT IIanalysis reveals that for a 95% confidence interval, the growth parameters of P.callensis are 67.39-80.08 mmin Bouhchicha wadi, but lower with 43.31-61.20 mm in the Blue Lake. In Bouhchicha wadi, the asymptoticlength L” reaches the highest value (79.80 mm) with a growth coefficient K of 0.480 years-1. In the Blue lake,L” reaches 59.85 mm with a growth coefficient K of 0.180 years-1. In the Total Length-Weight relationship,the regression equation shows a clear difference between Bouhchicha wadi (R = 0.91) and the Blue lake (R= 0.64). Both populations exhibit sexual maturity at different times of the year.

SOME MORPHOLOGICAL TRAITS AND HEAVY METAL ACCUMULATION IN MUSCLE TISSUE OF Ruditapes decussatus (Linnaeus, 1758)

This study aimed to investigate some morphological features and heavy metal accumulation in muscle tissue of Ruditapes decussatus (Linnaeus, 1758) in the spring and autumn seasons of 2018 in the Yumurtalık Coastline of İskenderun Bay located in the northeastern Mediterranean Sea. To this end, shell length (SL), total weight (TW), shell height (SH), shell inflation (SI), shell weight (SW), roundness index (RI), cup index (CI) and total length-weight relationship (LWR) of Bivalvia and heavy metal accumulation in the muscle tissue of Bivalvia were measured for two seasons. Minimum and maximum values of SL, TW, SH, SI, SW, RI and CI were determined as 21.50-39.00 mm, 0.80-22.15 g, 10.50-28.70 mm, 9.11-20.90 mm, 3.08-4.66 g, 1.03-2.14 and 0.58-0.67 respectively. The relationship between total length and total weight of R. decussatus was calculated to be W=0.0052*SL2.54 for spring and W=0.0031*SL2.88 for autumn. The growth type of Bivalvia specimens was determined as isometric growth (2.971). Heavy metal accumulation in the muscle tissue in spring and autumn seasons was found as statistically significant only for zinc and copper in different seasons (P

Length‐weight relationships of six fish species from the lower reaches of the Jinsha River, southwest China

The total length-weight relationships (LWRs) were estimated for six fish species from the lower reaches of the Jinsha River, southwest China. Specimens were seasonally collected using gillnets and drift gillnets (mesh size 2~14 cm), benthic fyke nets (mesh size 1 cm), baited hooks (stationary longline) and electricfishing (36 V/12 A, depth 3 m), in six sites from 2016 to 2019. The fish length (TL = total length, standard length (SL) as well as weight (W) were determined to the nearest 0.1 cm and 0.01 g, respectively. The LWRs for Jinshaia abbreviata (Günther, 1892) and Liobagrus marginatoides (Wu, 1930) are newly reported to FishBase. New maximum length or weight values were recorded for Pseudolaubuca engraulis (Nichols, 1925), Pseudobagrus truncatus (Regan, 1913), L. marginatoides, Abbottina obtusirostris (Wu & Wang, 1931) and Pseudobagrus pratti (Günther, 1892). All regressions were highly significant, with the coefficients of determination r2 > 0.950, and b values in the LWRs equations ranged from 2.399 to 3.484. For comparison and conversion, the SL-TL relationships were also estimated, with r2 values ranging from 0.980 to 0.999.

Morphology, Age and Growth of Bunni, Barbus sharpeyi Gunther, 1874 in Swab marsh, south Iraq

Morphology, age and growth of Bunni, Barbus sharpeyi Gunther, 1874 in Swab marsh, south Iraq, was studied from December 2004 to November 2005. A total of 864 B. sharpeyi (100-533mm TL) were collected using gill nets of different mesh sizes and electrical fishing. Twenty one morphometric and seven meristic characters for the species were described in the study. The morphometric characters were calculated as numerical ratio to standard and head lengths. The indices characters associated with standard length ranged from 0.0043 of eye diameter to 1.22 of total length, and with head length ranged from 0.178 of eye diameter to 0.752 of head width. The slopes of the regression lines ranged from 0.023 of eye diameter to 1.142 of total length. Fishes of 200-360mm length groups of B. sharpeyi were dominants in the samples. Total length–weight relationship of B. sharpeyi was W= 3.839 × 10-6 L 3.2017. The mean relation condition factor was 1.001. The annuli on scales formed during December and the growth of the scales was high during the period from February to August and was associated with water temperatures. The relation between standard length (L) and scale radius (S) was: L = 17.737 + 5.0469 S. The age composition ranged from 1 to 7. The standard lengths for these ages were 138.0, 202.0, 248.0, 304.8, 353.8, 393.1 and 439.2mm respectively. The growth of B. sharpeyi in Swab marsh was better than that of at Iraqi waters with the exception of B. sharpeyi at Hammar marsh. The mathematical model of growth as calculated by von Bertalanffy equation was Lt = 650 [1-e -0.138 (t + 0.642)].

Allometry of Mexican hogfish (Bodianus diplotaenia) for predicting the body length of individuals from two pre‐Columbian sites in the Pearl Island archipelago (Panama)

AbstractThe Mexican hogfish (Osteichthyes: Labridae, Bodianus diplotaenia Gill, 1862) is widely distributed throughout the tropical eastern Pacific from the Gulf of California to northern Peru, including all oceanic islands. Artisanal fishers occasionally capture it today and its remains are recovered at pre‐Columbian dwelling sites along the Pacific Coast of America. This paper addresses the advantages of using allometry to estimate size ranges of Mexican hogfish in pre‐Hispanic archeological samples from two ancient settlements in the Pearl Island archipelago of Panama: (1) Playa Don Bernardo (PdB), a preceramic site (6.2–5.6 kya), and (2) Bayoneta Island (BY‐10), a ceramic site (~1 kya). For creating the allometric model, a modern collection composed of 39 individuals covering a wide range of sizes and weights was used. All individuals have complete information about their total length (TL) and standard length (SL), which were recorded in millimeters (mm), and their total fresh weight (W) in grams (g). The TL of the sample ranged between 265 and 750 mm, and the SL between 210 and 487 mm. The W ranged between 273 and 3450 g. The most frequent bones (11) and otoliths were selected and 29 measurements were taken. The total length–weight relationship was W = 2E−05 TL3.0857 with R2 = 0.984. In general, it was observed that the relationships between the TL and the bone measurements had a strong correlation (R2 > 0.95). At PdB, the mean reconstructed length was 289.6 mm (TL), and at BY‐10, it was 283.6 mm (TL). The study of the archeological samples of B. diplotaenia could be used as a point of reference in modern ecological studies and fisheries management particularly in the Pearl Island archipelago.

Length-weight relationships and condition factors of the sand smelt Atherina boyeri (Risso, 1810) estimated from commercial and experimental catches in Lake Trichonis (Western Greece)

Total length-weight relationships (LWRs) from 3583 individuals of Atherina boyeri (Risso, 1810) caught in Lake Trichonis (Western Greece), using a commercial encircled net and experimental Nordic type benthic and pelagic multi-mesh gillnets, were estimated during 2019-2020. The variation of the parameter b for all seasons combined was significantly allometric, for both encircled towed and gillnets, with a quite robust fit (R^2 equals 0.925 and 0.947, respectively) and values equal to 2.254 and 2.089, respectively. The specimens were significantly lighter in summer than in the other seasons. The slopes of the LWRs significantly differ between seasons and exhibited relatively low values when compared to other ecosystems worldwide and in the same ecosystem in previous periods of time. Τhe estimated values of the Le Cren index were significantly higher than the Allometric and the Fulton ones.

A temporal approach for morphological indices of the common sole (Solea solea Linnaeus 1758) from the coast of the Aegean Sea, Turkey

Temporal changes of the morphological indices (Relative Gut Length (RGL), Fullness Index (FI), Hepatosomatic Index (HSI), Visceral Index (VSI), Gonadosomatic Index (GSI) and Fulton condition)) in 122 (♀: 94, ♂: 19, immature: 9) common sole were evaluated. Total length-weight relationships were calculated as W = 0.085TL3.01 and W = 0.0547TL2.40 in females and males, respectively, whereby isometric growth was observed in females and negative allometric growth was observed in males. While there was no statistically significant difference was observed between the FI, HSI, Viscerosomatic Index (VSI), RGL and GSI values of both sexes, however, there was a statistically significant difference in terms of Fulton K values (P < 0.05). In addition, there are statistical differences between the sexes total lengths and the values of RGL, FI, HSI, VSI, and Fulton-K (P < 0.05), as it is discernible in their HSI and VSI index values according to the month the specimens were obtained (P < 0.05). According to the results of the analysis, it has been determined that the female common sole along the Aegean coast adjust their energy temporally and store the energy they obtain from vegetative and carnivorous feeding. Contrary to the situation seen in females, the male individuals invest in energy through omnivorous feeding, according to the diet in the active process. Based on the results, it can be stated that the VSI and HSI are both important indicators of fish condition status. The results found here may be useful in both fishery research and fishery management.

Growth parameters ofPoecilia latipinna(Lesueur, 1821) (Actinopterygii, Poeciilidae) – an introduced species in brackish water of Wadi Al-Bahayes (Oman)

AbstractThis work is one of the first studies on the growth ofPoecilia latipinnaoutside its natural habitat. The objective of our study was to investigate the growth parameters of the population ofP. latipinna, which is an alien species in Oman (Wadi Al-Bahayes). The population structure ofP. latipinnain Wadi Al-Bahayes (Oman; 23°40′47″N; 58°11′36″E) was studied in June and August 2020, using 124 fish. In the course of this study, the number of individuals of each sex, age, weight and size composition were determined. In addition, the total length–weight relationship (LRW) was calculated, as well as the von Bertalanffy growth equation. The mean growth performance (phi prime) and the condition factor were calculated. Males accounted for 37.10% and females for 62.90% of the population. The length–weight relationship and the von Bertalanffy growth equation were W = 0.0214 × L2.7889R2= 0.9212, Lt = 11.46 (1 − e−0.127 (t + 2.71)) for males and Lt = 14.51 (1 − e−0.072 (t + 3.98)) for females. The mean growth performance and the condition factor were calculated as 1.22 for males and 1.18 for females and 1.54 for all specimens.The study shows that the population of the species is characterized by a wide age range. Consequently, monitoring of this alien species is highly recommended.

Saros Körfezi’nde (Kuzey Ege Denizi) Kahverengi Vatozun (Raja miraletus Linnaeus, 1758) Biyolojik Yönleri

The present study reports the age, growth, and reproduction parameters of 52 brown rays (Raja miraletus) captured from the Saros Bay (Northern Aegean Sea) between September 2006 -2008. The males and females accounted for 44.2% and 55.8% of the sample, respectively. The males measured 10.5-53.5 cm (disc width, 6.5-32 cm) and the females ranged 25.5-47.7 cm (disc width, 18-30.5 cm) in total length (TL). The equations TW=0.0017*TL3.27 and TW=0.0017*DW3.38 were used to describe the total length-weight and disc width-weight relationships, respectively. The length-at-age data on vertebrae were used to estimate the von Bertalanffy growth equation: L∞ = 62.43 cm, K = 0.28 year−1, t0 = −0.54 year. The maximum age was found to be 4 years for both the males and females.

Growth, mortality and stock assessment of greenback mullet, Planiliza subviridis from northwest Arabian Gulf, Iraq

The growth, mortality and stock parameters of greenback mullet, Planiliza subviridis from Iraqi marine waters, northwest Arabian Gulf was assessed using FiSAT II software for length-frequency data collected from February 2020 to January 2021. P. subviridis is one of the species caught in large quantities as commercial by artisanal fishers. Fish samples were collected by the Shaheen steel-hulled dhow and from the artisanal fishermen. The total length and body weight relationship of fish was estimated as W= 0.034L2.670, indicating negative allometric growth. Of 3350 specimens, growth and mortality parameters were evaluated. The asymptotic length (L∞), growth rate (K) and growth performance index (Ø') were 33.8 cm, 0.30 and 2.535, respectively. The total mortality rate (Z), natural mortality rate (M), and fishing mortality rate (F) were 1.11, 0.74 and 0.38, respectively. The present exploitation rate (Epresent) of P. subviridis computed as 0.34. Length at first capture (L50) was 17.47 cm. Recruitment of P. subviridis was observed throughout the year, with a peak during July. The yield per recruit analysis indicates that the current exploitation rate was below the biological target reference points (E0.1 and Emax), which refers to the stock of P. subviridis is underexploited. Virtual population analysis results showed that mid-lengths (16-22 cm) experienced the highest fishing mortality. The length at first capture (L50) was higher than the length at first maturity (Lm) of the species. So, for management purposes, more yields could be obtained by increasing the fishing activities on this species for a substantial harvest.