Negative Allometric Growth Research Articles

Potential to produce brown mussel integrated to a net-cage fish farm in a Mediterranean bay

In this study, we investigated the potential exploitation of the brown mussel Perna perna (Linnaeus, 1758) in an aquaculture farm (Monastir Bay, Mediterranean Sea, Tunisia). The quality of seawater as well as performance indicators such as Condition Index, length, weight, growth and frequency distribution of the mussel were determined over an annual cycle; from July 2017 to August 2018. Interestingly, P. perna has an extended sexual cycle during the year with two main spawning periods, the first in spring and the second in autumn, when suspended matter and Chlorophyll a were at their maximum concentrations in seawater. Spat mussels and young mussels showed significant growth rates from 1 July 2017 to 31 October 2017. Adult mussels exhibited negative allometric growth and a modal size of 41 to 50 mm. Results showed that several potentially toxic microalgae species developed at low densities in this marine zone. By using Solid Phase Adsorption Toxins Tracker (SPATT); lipophilic toxins including Okadaic acid and yessotoxins were detected at low levels in seawater and may be involved in the positive LSTs (lipophilic shellfish toxins) mouse bioassays in P. perna during the autumn. No other toxins such as paralytic shellfish toxins or amnesic shellfish toxins nor pathogenic bacteria or viruses were detected in P. perna. Altogether, our results suggest that finfish farms in Monastir Bay could be suitable sites for farming P. perna.

Age, growth, and mortality of Bogue (Boops boops, Linnaeus, 1758) from the Antalya Bay (Northwest Mediterranean Sea, Türkiye)

Bogue (Boops boops, Linnaeus, 1758) that was gathered in Antalya Bay had their ages, growth rates, and mortality examined. Using the von Bertalanffy equation, Lt = 37.50 (1 - e-0.15(t + 1.32)) (R2 = 0.988), growth in length was expressed for the entire sample without revealing any disparities between the sexes. The values of the allometric coefficient (b) of the length-weight relationships specify negative allometric growth (b < 3) in females, males, and overall sexes. Total and natural mortality were found to be Z= 1.12 y-1, and M= 0.36 y-1. The exploitation ratio E = 0.68 indicated that the population was overexploited.

SPECIES COMPOSITION, SIZE DISTRIBUTION, CONDITION FACTOR AND GROWTH PATTERN OF CICHLIDS FROM ZOBE RESERVOIR, DUTSIN-MA, KATSINA STATE, NIGERIA.

The species composition, size distribution, condition factor and growth pattern of cichlids from Zobe reservoir Dutsin-Ma, Katsina State was investigated between August and November 2022, with a view to understanding the distribution and well-being of cichlids in the water body. One hundred (100) cichlids were sampled from two (2) major landing sites (Makera and Garhi) of the reservoir, the fish were identified and separated before being transported in an ice box to the laboratory Biology Laboratory of the Federal University Dutsin-ma. At the laboratory, the length was measured to the nearest centimeter using a ruler while a sensitive weighing scale was used to measure the weight in grams. The results showed that four species were identified; Oreochromis niloticus (40), Oreochromis aureus (21), Sarotherodon galilaeus (21) and Coptodon zilli (18). The mean total length and weight were significantly higher (P<0.05) in O. niloticus compared to other species. The least was observed in O. aureus although it was not different significantly compared with C. zilli and S. galilaeus. The condition factor (K) of >1 was obtained in all the species with O. niloticus having the highest value of 2.26 which was significantly higher than 1.48 observed in O. aureus. All the species showed negative allometric growth, however, C. Zilli and O. aureus were very close to isometric growth with b values of 2.96 and 2.85 respectively. Although negative allometric growth was observed in all the species, the K values of >1 showed that all the cichlids in the Zobe reservoir are healthy and in good biological condition

Length–weight relationships and condition factors of six notothenioid fish species occurring off King George Island and Northern Victoria Land (Antarctica)

This research was conducted to study length–weight relationships (LWR) and condition factors of six Antarctic notothenioidei fish species including blackfin icefish (Chaenocephalus aceratus), single-angle icefish (Chionodraco hamatus), marbled rockcod (Notothenia rossii), black rockcod (Notothenia coriiceps), emerald rockcod (Trematomus bernacchii), and dusky rockcod (Trematomus newnesi) from the King Sejong Station on King George Island and Jang Bogo Station on the Northern Victoria Land. A total of 232 specimens were collected by fishing on the icebreaking research vessel ARAON from December 2020 to February 2021. The LWR parameters and condition factors differed depending on species, which can be affected by their distribution, species characteristics, and gravidity status. The exponent b values in LWR (W = aLb) ranged from 2.593 to 5.184. Four species including C. aceratus, C. hamatus, N. rossii, and T. bernacchii followed positive allometric growth, T. newnesi followed negative allometric growth, and only N. coriiceps showed isometric growth. These results can be helpful in understanding the ecological and growth conditions of six fish species living in the Antarctic Ocean, providing more information for future research on Antarctic fish.

Aquaculture and its conservation potential of critically endangered Jipe Tilapia (Oreochromis jipe) in Lake Jipe

Tilapia jipe (Oreochromis jipe) is listed as a critically endangered Cichlidae endemic to fast-shrinking Lake Jipe. Climate change and anthropogenic activities have significantly impacted the lakes’ ecology and species’ genetic integrity. Four months of Jipe tilapia culture growth performance was conducted in four selected farms within the Chala area, Taveta Sub-County of Taita Taveta County along the slopes of Mt. Kilimanjaro’s Kenya side. The study assessed the growth performance of 3rd generation mixed-sex Oreochromis jipe under aquaculture conditions. Fish sampling was done monthly to assess the growth performance of fingerlings stocked at an average weight of 5 ± 0.02 g and a stocking density of 5/m3. Total weight ranged between 123.72 g, and 74.70 g from the entire growth trial sample population. The highest and the least mean weight gains recorded were 108.87 ± 4.31g and 87.12 ± 4.40g for Farm B and D respectively. Similarly, farm B recorded the highest mean length (18.80 ± 0.27) while farm C recorded the least (17.31 ± 0.25) with no significant difference between the selected farms. Water quality parameters were within the normally acceptable tilapia culture ranges. The study findings indicated a negative allometric growth (b < 3) for all farms except Farm A. All growth trials demonstrated a good Condition factor (K) with a range of 1.82 to 2.19. The present study concluded that O. jipe has the potential for aquaculture and species genetic conservation and restocking due to its ease of propagation. The study recommends further G x E breeding program strategies, nutritional and general management studies, and a policy limiting genetic material transfer from its catchment.

Shell Dimension-Weight Relationship and Condition Index of the Invasive Mussel Mytella strigata in Sasmuan, Pampanga, Philippines

A total of 300 Mytella strigata were collected at three sampling points in the mussel coastal demonstration farm in Sasmuan, Pampanga, and subjected to morphometric and gravimetric measurements for the evaluation of its growth pattern and condition index. Designated sampling sites were based on the distances to the river mouth (200 m, 400 m, and 600 m) with varying water quality parameters (temperature, salinity, pH, water velocity, and chlorophyll-a). Mussels in Site 2 had significantly larger shell dimensions (SL = 2.862 cm, SW = 1.458 cm, SH = 0.926 cm), shell weight (0.640 g), and total live weight (1.150 g). Significantly higher (p < 0.05) soft-tissue dry weight (0.083 g), however, was obtained in Site 3, while comparable (p >0.05) soft tissue weight was observed in Site 2 (0.364 g) and Site 3 (0.413 g). Nevertheless, mussels in all sites demonstrated negative allometric growth (b < 3). The length-weight relationship revealed a weak to moderate, positive correlation. A significantly higher (p < 0.05) condition index was obtained in Site 3, which could have been influenced by higher chlorophyll-a and substantially lower water velocity. As such, this signifies its potential to have a well-established population in this spatial distance (600 m) from the river mouth. Hence, regular harvest and product development is recommended as strategic options to control its proliferation.

Determining Sexual Development and Size at Sexual Maturity of Sardinella tawilis and its Implications on Management

Reproductive biology is important in formulating management interventions for fish stocks. Limits on catch size are established based on the identified size at first sexual maturity of the target fish species, which can be accurately determined through histological analysis of gonads. The study investigated the reproductive characteristics of the endangered Sardinella tawilis and determined the size at first sexual maturity based on histological analysis. Between 2017 and 2018, 312 fish samples with different lengths were collected in Taal Lake's northern and southern basins. The length-weight relationship of S. tawilis shows that the species exhibits negative allometric growth. Female S. tawilis, characterized by larger sizes, are significantly more abundant in our catches than male individuals (mean sex ratio p<0.05) and exhibit an asynchronous oocyte development. Histological analysis of gonads showed that the size at sexual maturity for both male and female S. tawilis were at 75 to 79 mm FL, which was smaller than the reported size at sexual maturity based on morphological analysis. Smaller average and maximum lengths, as well as the size at first sexual maturity, could suggest that S. tawilis has experienced growth overfishing and a slowly degrading lake environment through time. Results highlighted the importance of ensuring that immature S. tawilis can enter sexual maturity and contribute to the population through reproduction. It is also highly recommended that the size of S. tawilis to be targeted by fisheries are individuals above 100 mm FL, which exhibited the highest proportion of spawning capable individuals.

Estimation of differential growth of the protandrous hermaphrodite marine gastropod Trochita trochiformis (Littorinimorpha: Calyptraeidae) using Schnute model cases

The snail Trochita trochiformis is a mollusk captured on the coasts of Jalisco and Guerrero of the Mexican Pacific. Despite its importance in artisanal fisheries, information on its population parameters is still being determined. This research aimed to determine the diameter-weight relationship, sex ratio, cohorts, and growth of this species. Specimens were captured from October 2019 to September 2021. Shell diameter (Sd), total weight (Tw), and the sex of the organisms were gathered from a total of 1763 females and 956 males. The sex ratio was 1.84:1, and the X2 test (P < 0.05) indicated significant differences. The Sd-Tw relationship for females and males was potential-type. The values of the allometry coefficient for both sexes were b = 2.61, b = 2.60 for females, and b = 2.62 for males. In all three cases, the t-Student test indicated negative allometric growth, which indicates that the species first grows in shell diameter, then in body weight. The ANCOVA did not show significant differences in the Sd-Tw relationships between sexes (P = 0.902). The Kolmogorov-Smirnov test applied to the Sd data showed differences between sexes (P < 0.001). In females, differences were observed in 71.5% by monthly comparisons, while in males, differences were found in 58.1%. Multinomial analysis showed three modal groups and 14 individual cohorts for both females and males. Case 2 of the Schnute model was the best for females (wi = 0.39) and males (wi = 0.53), showing sigmoidal Gompertz-type growth. The resulting growth curves showed that females exhibit accelerated growth concerning males and that both sexes reach their maximum size, 88.04 and 86.23 mm, respectively, at approximately 10 years of age.

Biology of the cleftbelly trevally Atropus atropos (Bloch and Schneider, 1801) from Ratnagiri coast of India

The cleftbelly trevally Atropus atropos (Bloch and Schneider, 1801) is one of the important carangid species landed mostly as trawl bycatch along Ratnagiri coast. Investigations were carried out on A. atropos with respect to length-weight relationship, condition factor, morphometrics, feeding and reproductive biology. The length-weight relationship indicated negative allometric growth in A. atropos. Morphometric measurements showed significant correlation with total length. The gut content analysis revealed A. atropos to be a carnivore fish feeding mainly on Acetes spp., small teleostean fishes, cephalopods, and squilla. Sex ratio showed dominance of males. Gonadosomatic index and maturity studies indicated that A. atropos has a protracted spawning season extending from May to December. Length at sexual maturity for females was estimated to be 171 mm. Fecundity ranged from 16458 to 138688 eggs with an average of 70097 eggs. Ova diameter studies showed that A. atropos spawns twice in a protracted spawning season. Keywords: By-catch, Carangidae, Carnivore, Reproductive biology, Spawning season

Body Indices and Population Dynamics of Setipinna breviceps (Cantor, 1849) from Batang Lassa Estuary, Sarawak, Malaysia

The Setipinna breviceps is a commercially important and highly esteemed food fish. This species has scant of scientific formation particularly on population parameters like growth, mortality and recruitment. The present study aimed to estimate the body indices and population parameters of Setipinna breviceps of Batang Lassa Estuary (BLE). Samples were collected between April 2019 and September 2020. A local made bag net known as Gnian (mesh size 1.25 to 4.00 cm) was used for sampling the fish. A total of 287 qualified specimens were used for this study. The length and weight of individual fish was measured to the nearest 0.1 cm and 0.01 g, respectively. The length ranged from 5.50 to 24.00 cm and growth coefficient (b) was 2.563 (R2 = 0.87) which clearly indicated a negative allometric growth. About 50% of individuals showed flat or slender body (Kn<1) and 47% of the specimens were rounded shaped (Kn>1) while 2.44% of fishes measured an ideal shape (Kn = 1). The parameters of growth L∞, K and ϕ’ were estimated at 24.15 cm, 0.23 yr-2 and 2.13, respectively. The estimated natural mortality and fishing mortality were 0.74 and 0.29 yr-2, respectively and exploitation rate was 0.28. The recruitment pattern during the study was observed at two possible unequal peaks. The present study concluded that the anchovy was under exploited (E<0.5) as demonstrated by the under-sized fishes caught with small mesh size net. However, considering the minimum lengths and length at first catch, the BLE could be a productive nursery ground for S. breviceps. Therefore, management actions are required to avoid juvenile catches.

Intraspecific phenotypic differences in climbing perch Anabas testudineus (Bloch, 1792) populations may be linked to habitat adaptations

The climbing perch, Anabas testudineus, is a nutritionally and economically significant food fish. The present study reveals the first comprehensive description of the life-history traits of A. testudineus scooped up through different traditional fishing gears from July 2020 to December 2020. Among the 120 collected specimens, the smallest and largest specimens were 8.5 cm–14.6 cm TL in Nilphamari and Patuakhali, respectively. The estimated b values for LLRs indicated positive allometric growth in all sampling points (b > 1.0). The LWRs of A. testudineus indicated positive allometric growth in the Gazipur and Nilphamari districts (b > 3.00) and negative allometric growth in the Patuakhali and Khulna districts (b < 3.00). A Wilcoxon sign-ranked test for WR showed no significant dissimilarity from 100, signifying the balanced habitat for A. testudineus. The estimated a3.0 was minimum in Khulna (0.0110) and maximum in Nilphamari (0.0825). “The Lm was estimated at 7.4032 (7.4) cm TL in Nilphamari and 8.86 (8.9) cm TL in Patuakhali”. Nineteen of twenty morphometric measurements and ten of twelve meristic characters showed substantial variations (p < 0.0001). The principal component analysis indicated shape variation and explained 85.361% of the total variance and showed differences in TL, SL, HL, LBD, LE1, D1D2, A1A2, and VV2. The cluster heatmap demonstrates that the other stocks segregated Gazipur stock. Our findings reveal a significant dataset about intraspecific phenotypic differentiation, which will aid the long-term exploration and management of A. testudineus species in Bangladesh and its neighboring countries.

First record of important biological parameters of Badis badis: A small indigenous species in Bangladesh

A total of 286 Badis badis were collected from the Sutiyahali Reservoir in Mymensingh from January to December 2022, and their sex ratios, first sexual maturity, length-weight relationships and condition factors were evaluated. The weight and length of B. badis varied from 0.81 to 1.01g (0.89±0.30) and 4.08 to 4.60cm (4.36±0.31), respectively. Logistic curves depicting a sex ratio and 50% maturity (L50) estimated at 4.5cm for females and 4.05cm for males, as well as males reaching first sexual maturity with a shorter length than females. Regression coefficients in every month differ significantly (p&lt;0.05), according to the regression equations. Each month, the values of the exponent b were less than 3 (b&lt;3), with the highest value of b recorded in August (2.80) and the lowest value recorded in January (2.33). This led to a monthly negative allometric growth being seen. A strong positive relationship is evident from the coefficient of determination (r2) values, which ranged from 0.92-0.98 with an average of 0.961. During the study, the average condition factor (Kn) value for B. badis was found to be 1.02±0.13, which is a positive indicator of the fish's physical well-being. The condition factor values varied between 0.84 to 1.39, making it abundantly clear that B. badis are in good health and the waterbody is an ideal habitat for their survival. Relative condition factor (Kr) values, which varied between studies and ranged from 0.78 to 1.01, also exhibited a noteworthy difference (p&lt;0.05). For its long-term management, the above findings will be very helpful.

Reproductive biology and gonadal cycle of Indian Potasi, Neotropius atherinoides (Bloch 1794) in Bangladesh

The present study was conducted to investigate the reproductive biology of Neotropius atherinoides in Bangladesh Fisheries Research Institute, Floodplain Sub-station, Santahar, Bogura, Bangladesh. A total number of 70 fish samples were collected on monthly basis from Atrai River and Jamuna River during the period from September 2021 to August 2022. The highest mean value of the gonado-somatic index (GSI) was recorded in July (12.55±2.50), whereas the lowest was found in January (0.46±0.11). Highest individual fecundity (7000±1900) and ova diameter (0.50±0.07 mm) was also observed in July. From the histological observation of the ovary, early peri-nucleolar stage, late peri-nucleolar stage, yolk vesicle stage, yolk granule stages were identified where the highest percentage (80%) of mature oocytes were observed in July. Based on the GSI, fecundity, and gonadal histology, the breeding season of N. atherinoides was observed from May to August and recorded a remarkable peak in July. In case of length weight relationship (LWR), the coefficient of determination value (r2) was found 0.95 and slope was found b=1.02 which indicated the pattern of negative allometric growth of this species as b&lt;3. In contrast, an increase was recorded in the fecundity associated with the rise of total length, body weight, and gonad weight, showed a significant linear relationship. This study would assist in the development of induced breeding techniques and provide valuable information for the sustainable management of this population in the inland open ecosystem.

Reproductive Biology of Pialy Fish, Aspidoparia jaya (Hamilton, 1822) in Bangladesh

A study to investigate the reproductive biology of Aspidoparia jaya was conducted in Bangladesh where a total of 80 fish samples were collected on monthly basis from Atrai River and Jamuna River during the period from January 2022 to December 2022. The highest values of the gonado-somatic index (GSI) was recorded in July (11.37±1.75%) and January (9.55±1.35%), whereas highest individual fecundity of 6990±1280 and 5755±1050 and ova diameter of 0.55±0.05 and 0.52±0.03 mm, respectively were also observed during these months. From the histological observation of the ovary, seven different stages of occytes were identified where highest percentage of mature oocytes was observed in July and January. Based on the GSI, fecundity, and gonadal histology, two breeding season of A. jaya was observed from May to August and from December to late January with a remarkable peak in July and January. In case of length weight relationship (LWR), the coefficient of determination value (r2) was found 0.95 and slope was found b= 2.02 which indicated the negative allometric growth pattern of this species as b&lt;3. In contrast, an increase was recorded in the fecundity associated with the rise of total length, body weight, and gonad weight, showed a significant linear relationship. This study would assist in the development of induced breeding techniques and provide valuable information for the sustainable management of this population in the inland open ecosystem.

First Knowledge on Data Poor Stock: LWR and Condition Factor of a Recently Established Population of Atherina boyeri in Atikhisar Reservoir, Turkiye

Fisheries management practices require reliable data for the assessment of data poor stocks. This paper reported the first knowledge on length-weight relationship (LWR) and condition factor of Atherina boyeri in Atikhisar Reservoir, Çanakkale, Türkiye. A total of 1103 individuals of which 132 were immature was captured in June 2021. The sex ratio male to female was 1:1.75. The relationship between weight (W) and total length (TL), standard length (SL), and fork length (FL) were estimated as W=9E-06TL2.9212, W=1E-05SL2.9082, and W=9E-06FL2.9495. A. boyeri exhibited a negative allometric growth. The mean of Fulton`s condition factor of A. boyeri population in Atikhisar Reservoir was determined as 0.619±0.061. The mean Fulton`s condition factor for female individuals were higher than the males` condition factor and the difference between sexes was statistically significant. The present study made available valuable information on the data poor stock by providing LWR and condition factor of A. boyeri in Atikhisar Reservoir, a new freshwater system for the very euryhaline amphidromous species. The findings of the present study will substantially contribute to the knowledge of the population dynamics of the commercially important species for fisheries managers and decision-makers to maintain sustainable population levels.

Biometric indices, growth pattern, and physiological status of captive-reared indigenous Yellowtail brood catfish, Pangasius pangasius (Hamilton, 1822).

The current study was conducted to comprehend the variation of the growth pattern and the physiological status of Pangasius pangasius (Hamilton, 1822) reared in the pond from July 2021 to September 2021. A total of 90 brood individuals were collected from the Meghna River and studied for the present experiment. The overall growth pattern for P. pangasius was isometric (b = 3.00) in the Meghna River, while the male fish showed positive (b > 3.00) and the female showed a negative allometric growth pattern (b < 3.00). The Fulton's condition factor (KF) value was greater than 1, indicating a healthy population and a habitat with abundant food sources. Moreover, the KF value was found to be substantially related to total body mass. On the other hand, both sexes of P. pangasius had relative weight average values of more than 100, simply indicates the fish is naturally obese and has enough stored energy to maintain its physiology. The calculated form factors suggested an elongated body shape, which is typical of many riverine fishes. In addition, a small number of morphological traits varied significantly in the current study. Likewise, in the case of morphometric features, the principal component analysis showed a considerable degree of connectedness between the male and female individuals. The blood values showed no significant difference between the sexes. This might result from feeding fish the same kind of food and maintaining them in the same environment. However, the higher temperature might have caused slight blood abnormalities in both sexes. The current findings strongly support raising this fish in captivity and would offer useful information for fish farm owners, entrepreneurs, stakeholders, and other concerns in Bangladesh and surrounding nations.

Reproductive cycle and sexual maturity size of landed Selene peruviana (Perciformes: Carangidae) on the coasts of the Ecuadorian Pacific

The Peruvian moonfish (Selene peruviana) is an important fisheries resource that is landed in the main fishing harbors of Ecuador. At the local level, little information is available regarding the biology of this species, which hinders the development of management plans. The present study evaluates the reproductive characteristics of S. peruviana such as the size at sexual maturity and reproductive cycle. Specimens were obtained from artisanal and industrial catches from January 2017 to December 2018. The morphometric characteristics, sex, and maturity stage of 886 specimens were determined, and the gonadosomatic index (GSI), hepatosomatic index (HSI), and relative condition factor (Kn) were estimated. The length-weight relationship and length at sexual maturity (L50) were evaluated with an allometry equation and multi-model analyses, respectively. The mean capture size (total length, TL) was 23.62 cm for males and 22.97 cm for females. A sex ratio (M:F) of 0.70:1.00 (χ2 = 26.28, P &lt; 0.05) was obtained. The allometric factor of the length-weight relationship for both sexes (b) was 2.63 (t = 12.16, P &lt; 0.05), and the coefficient of determination (r2) was 0.89, which suggests that negative allometric growth was present. The L50 (TL) was estimated to be 22.61, 23.86, and 23.27 cm for males, females, and sexes combined, respectively. The monthly GSI, HSI, and Kn values were significantly different (K-W, P &lt; 0.05) among study months. The maximum GSI values were observed in February and March, which constituted the period of highest reproductive activity. The HSI and Kn values exhibited similar trends. The size at sexual maturity was similar to the average catch size, which could indicate that S. peruviana is currently at the limit of its optimal catch size.

Pola pertumbuhan dan laju mortalitas Kepiting Bakau (jantan dan betina) jenis Scylla tranquebarica dan Scylla olivacea di Perairan Teluk Bintuni, Provinsi Papua Barat

The purpose of this study was to determine the shape of the growth pattern of the relationship between carapace width and weight, growth parameters, and mortality and exploitation rate of mangrove crabs in the waters of Bintuni Bay Regency. This research was conducted in Teluk Bintuni Regency, West Papua Province. The sampling locations were spread in three locations, namely Bintuni, Manimeri and Babo. Mangrove crab samples obtained from fishing traps caught by fishermen in the waters of Bintuni Bay, identified gender (male or female), and measured carapace width and weight, then the measurement data were analyzed using the help of several data analysis formulas. Based on the results of the analysis, it is evident that the mangrove crab S. tranquebarica has a value of b = 3.6223 (male) with a positive allometric growth pattern and b = 2.8100 (female) with a negative allometric growth pattern, while the type of S. olivacea has a value of b = 2.8612 (male) and b = 2.1581 (female). The growth parameter values for male and female of S. olivacea were able to reach asymptotic carapace width (CW∞) = 20.90 cm, while males and females of S. tranquebarica (CW∞) = 18.90 cm and 19.21 cm, respectively. Natural mortality of S. tranquebarica in the waters of Bintuni Bay is estimated at 0.90 per year (male) and 1.31 per year (female), while S. olivacea is 1.02 per year (male) and 1.12 per year (female).

Length-weight relationship and growth of Labeo bata

This study was executed to elucidate the length-weight relationship (LWR) yet the annual condition of the Labeo bata (Hamilton, 1822), an immensely important fishery of Bangladesh. Overall, 447 specimens employed during this study were collected by using traditional fishing gear (cast net). Total length (TL) of each individual was measured closest to 0.1 cm and whole body-weight (BW) nearest to 0.01 g accuracy, respectively. The values of ‘b’ indicated negative allometric growth patterns for males (b= 2.913) whilst an isometric value for females (b= 3.038) and both sexes (b= 2.989), respectively. Furthermore, the Fulton condition factor value was highest for males (0.98) over females (0.97). All of these outcomes will bring advanced scientific knowledge and will be helpful for sustainable management of this least concern fish species (Labeo bata) in the river ecosystem of Bangladesh.

Population dynamics and stock assessment of two major eels (Muraenesox bagio and Congresox talabonoides) from the marine waters of Bangladesh

Muraenesox bagio (black eel) and Congresox talabonoides (brown eel) are two major eels (Muraenesocidae) species which are commercially significant in the marine catch of Bangladesh, but population dynamics and stock assessment of marine eel fishery in Bangladesh are yet to be studied. This study is the first endeavour to analyze the population dynamics and stock assessment of this marine eels collected from July 2021 to May 2022 using three length-based methods namely TropFishR, the Length Based-Spawning Potential Ratio (LB-SPR) &amp;amp; the length-Based Indicators (LBI) and two catch-based methods including Depletion-Based Stock Reduction Analysis (DB-SRA) and the Catch-Maximum Sustainable Yield (CMSY). A slightly positive allometric growth pattern (b=3.10) for the black eel and a negative allometric growth pattern (b=2.33) for the brown eel were observed in the length-weight relationship. The parameters of von Bertalanffy Growth Function (VBGF) and the linearized length-converted catch curve (LCCC) analysis for black eel and brown eel were L∞=190.67cm and 166.63cm, k=0.18 year-1 and 0.16 year-1, and the total mortality, Z=0.70 year-1 and 0.45 year-1. The eel fishery is calculated to be overfished due to overexploitation and the stock’s spawning biomass (SPR=19% for black eel and 21% for brown eel) is close to the limit reference point but well outside the targeted range because the majority of the catches were found to have below-maturity levels. This study advised an optimum length limit to catch from 93 to 114 cm for black eel and 83 to 101 cm for brown eel. Though the estimated reference points of the CMSY were more optimistic than those from the DB-SRA, the tendency of the status of eel stock has been displayed moving towards overexploitation from a safe stock scenario. This study, therefore, recommended an annual landing limit of 250 mt as OFL (Over fishing limit) for the next ten years in association with existing management measures to maintain the present stock biomass of eel fishery over the BMSY level.