Length Frequency Distributions Research Articles

Length-Frequency Distribution and Relative Condition Factor of Brycinus nurse in the New Calabar River, Niger Delta, Nigeria

This study assessed the length-frequency distribution and condition factor of Brycinus nurse from two sampling stations in the New Calabar River. A total of 401 individuals of B. nurse were collected from artisanal fishers and assessed between February 2020 and January 2021. The collected samples were analyzed for growth pattern using FISAT II. The mean values were 11.80±1.59 cm and 9.52±1.28 cm for total length and standard length The mean weight was 20.63±8.38 g. The length-weight relationship revealed an exponent b value of 2.539, showing negative allometric growth. The condition factor ranged from 1.09 to 1.42 indicating that the species is in good growth condition. The size structure of B. nurse recorded indicated that most individuals were relatively medium to small sizes and were not allowed to grow to adults as a result of overfishing. Therefore, proper management and intervention is needed to manage overexploitation of B. nurse in the New Calabar River.

Effects of a trawling ban on the growth of young-of-the-year European hake, Merluccius merluccius in a Mediterranean fishing exclusion zone

This study evaluates the effects of a trawling ban on the growth of young-of-the-year (YOY) European hake, Merluccius merluccius (L., 1758) by comparing size structure, length–weight​ relationship, condition and growth in three gulfs along the coast of northern Sicily (central Mediterranean Sea), one of which has been subject to a trawl ban for 15 years. Hake ranging between 60 and 330 mm were collected from 50 to 200 m depth in May 2005. The length frequency distribution of YOY fish showed a higher modal length in the untrawled gulf and comparable densities in the three gulfs, while larger fish were more abundant in the untrawled gulf. Length–weight relationships and condition factors did not highlight any trend linked to the effects of fishing and suggested a large variability of the system. Growth curves had comparable slopes while different intercepts in both length–weight and growth curves suggest that the observed larger modal size of the first cohort in the untrawled gulf could be linked to better condition and growth during the initial life stage in the pelagic environment.

Population structure and biological aspects of lobster (Panulirus spp.) of the Madura Strait landed in Situbondo of East Java, Indonesia

Lobster is an important economic fishery resource in domestic and international trade. The high economic value of lobster due to increasing market demand has led to its intensive exploitation. The enactment of specific regulations on lobster proves the urgency of its management. Madura Strait is one of the unique biogeographical sea regions of East Java. This research was conducted in January-March 2021 at Pasir Hitam Beach, Situbondo. The purpose of this study was to determine the species composition of lobsters, the frequency distribution and the growth form, and the sex ratio. The analysis applied is class distribution of length and weight classes, regression analysis, and chi-square. The lobster catches consist of 4 species, namely Scalloped spiny lobster (Panulirus homarus), Ornate spiny lobster (P. ornatus), Painted spiny lobster (P. versicolor), and Mud spiny lobster (P. polyphagus). P. homarus is the most dominant species. The frequency distribution of carapace length and weight of P. homarus, P. ornatus, and P. versicolor has met the minimum size limits rules. The length and weight relationship of P. Homarus and P. ornatus were negative allometric, while P. versicolor isometric. Lobster sex ratio is in a balanced condition.

Population parameters of several groupers (Famili Serranidae) in Labuan Bajo waters, East Nusa Tenggara

Labuan Bajo has a fertile aquatic ecosystem, one of them is the coral reef ecosystem. This condition happened because of the supply of nutrients that are carried through Indonesia Through Flow and the local upwelling phenomena. Various species of reef fish of various sizes have been caught in Labuan Bajo waters. In general, the type of reef fish that dominates is grouper fish catch by using handline fishing gear. Furthermore, there is damage that occurs in the coastal ecosystem causes changes in ecological functions and disrupted ecosystem benefits. In addition, pressure from overuse did not provide opportunities for resources to carry out recovery makes the condition of resource stocks threatened. This study aims to determine the parameter aspects of the population of several types of grouper fish in Labuan Bajo waters. The types of grouper studied included Plectropomus leopardus, P. maculatus, P. oligacanthus, and Variola albimarginata. Data collection was carried out by enumerators from April to August 2019 which included the daily data on the length and weight distribution of groupers. Length-frequency distribution data is analyzed by estimating fish population parameters using the Electronic Length Frequency Analysis (ELEFAN I) program which is packaged in the FAO-ICLARM Stock Assessment Tool II (FiSAT II) software. The results of the analysis showed the equation of growth parameters for Von Bartalanffy for P. leopardus is Lt = 89.06(1-e−0.24(t+0.52)); P. maculatus is Lt = 76(1-e−0.54(t+0.23)); P. oligacanthus is Lt = 72.32(1-e−0.66(t+0.19)); and V. albimarginata is Lt = 45(1-e−0.51(t+0.29)). The length at first birth of each species is Lt=0 P. leopardus = 10.45 cm, Lt=0 P. maculatus = 8.88 cm, Lt=0 P. oligacanthus = 8.52 cm, and Lt=0 V. albimarginata = 6.19 cm. Meanwhile, the exploitation rate (E) of P. leopardus, P. maculatus, P. oligacanthus, and V. albimarginata were 0.81; 0.53; 0.45; and 0.70.

The length–weight relationships and clasper maturity of two shark (Carcharhinus sorrah, Carcharhinus falciformis) of landed in Prigi Coastal fishing Port Trenggalek East Jawa

Sharks are often found in all the waters are scattered in various regions of the world. On the other hand, shark fisheries have declined globally due to shark fishing as well as the demand is very high. The length-frequency distribution for Carcharhinus sorrah distributed between 33-131 cm in Carcharhinus falciformis is distributed between 51-161 cm. The length-weight relationship of Carcharhinus falciformis between is allometric negative, while on Carcharhinus sorrah allometric positive. The maturity level of shark in august in the Full Classification (FC) category,5.6% in the Non Full Calcification (NFC) category 7.4% and in the Non-Calcification (NC) category 87.0%, September in the Full Classification (FC) category, 48.7% in the Non Full Calcification (NFC) category, 17.9 % and in the Non-Calcification (NC) category 33.3 %, October in the Full Classification (FC) category, 72,7 % in the Non Full Calcification (NFC) category, 6.1 % and in the Non-Calcification (NC) category 21.2 %. The maturity level of the clampers in FC (Full Classification) conditions occurs in October and Males are the most common. The sex ratio of the spot-tail shark (Carcharhinus sorrah) was dominated by male fish, with the maturity class being dominated by non-calcification (NC). whereas in silky sharks (Carcharhinus falciformis is dominated by females, while in january many Immature / Non-Calcification (NC) months of march are dominated by Ripe / Full-Calcification (FC). This study provides information about the length-weight relationship and clasper matured for two shark species whose results will be used for stock assessment and sustainable management of sharks.

Abundance and Distribution, Growth Pattern, Sex Ratio and Gonadosomatic Index (GSI) of Liza falcipinnis (Valenciennes, 1836) from Ojo Axis of Badagry Creeks, Lagos, Nigeria

A study on seasonal abundance, morphometric and meristic data, growth pattern, condition factor, sex ratio and gonadosomatic index of Liza falcipinnis (Valenciennes, 1836) from the Ojo axis of Badagry creek, Nigeria was conducted from May 2019 to March 2020. A total of 1012 species were randomly selected, having 499 females and 513 males. The length frequency analysis and length-weight relationships (LWR) were determined. Sex ratio was determined by Chi-square analysis. The results showed that morphometric data are: 0.5 - 2.5 mm for ED, 2.1 - 12 mm for HL, 1.7 - 8.1 mm for HD, 2.5 - 11.7 for BD, 2.6 - 233.3 mm for TL and 9.23 - 1006 g for BW for the combined sexes. The slope (b) shows an allometric growth pattern. The intercept ‘a’ and slope ‘b’ of the LWR (LogW = a + bLogL) were Log W=15.39+ 0.34 LogL (r= 0.54) for combined sexes, Log W= 12.49+ 0.02 log L (r= 0.38) for males and Log W= 18.23+ 0.01 log L (r=0.16) for females.The length frequency distribution indicated that species were dominated by two year classes (Ages 1 and 2). Condition factors were generally low. The values ranged between 0.68 - 0.85 for combined sexes. The gonadosomatic index for female was highest in August, 2019 (17.77%) with Mean±SD of 2.88±0.75; which indicated the peak of spawning period in the study area.Sex ratio difference was significant (P<0.05). Sexual differences were significant; the females are phenotypically larger than the male.

MATURITY MEASUREMENT ON BIGEYE SCAD (Selar crumenophthalmus BLOCH 1793) TO INDICATE OVERFISHING

Bigeye scad (Selar crumenophthalmus) is one of the small pelagic economical species from the family of Carangidae. The annual landing of Carangids in Ambon Island sharply dropped in 2018. Meanwhile, demand for these fish has increased following the local population growth. Was the reduction of fish products showing an indication of overfishing? To answer this, we measured the maturity of bigeye scad caught in Ambon waters during east monsoon (May to July 2019 and March to June 2020), including the length-frequency distribution. We found that the minimum size was 5 cm, the maximum (Lmax) was 23 cm, and the optimum length (Lopt) was 18.7 cm. The estimated length of first maturity (Lm) of bigeye scad was 18.3 cm. This study showed that the optimum length was slightly longer than maturity length. Less than 30% of the catch of bigeye scad was immature and indicated a small probability of recruitment overfishing. Arround 57% of megaspawner found during this study showed more robust broodstocks to produce survival larvae into the population. The possibility of overfishing is relatively low for the bigeye scad fishery during the east monsoon, except for the reduction in the maturity size should be concerned.

Life‐history traits of Guntea loach, Lepidocephalichthys guntea (Hamilton, 1822) in the Payra River, southern Bangladesh

AbstractThe present study provides the first wide‐ranging elucidation of life‐history traits, including length–frequency distribution (LFD), length–weight and length–length relationship (LWR and LLR), form factor (a3.0), best condition factor (allometric, KA; Fulton, KF; relative, KR; and relative weight, WR), length at first maturity (Lm), natural mortality (Mw) and optimum catchable length (Lopt) of Lepidocephalichthyes guntea from the Payra River in southern Bangladesh. A total of 470 fishes were randomly collected seasonally from February 2019 to January 2020, using several traditional fishing gears (cast nets; drag nets; lift nets; and gill nets). The total length (TL), standard length (SL) and total body weight (BW) of each individual fish were measured with a 0.01 cm and 0.01 g precision, respectively. The TL size classes of 6.00–6.99 cm and 7.00–7.99 cm TL were the numerically dominant groups among the total fish population. Exponential b values of LWR (TL vs. BW) indicate a positive allometric growth (b = 3.20) pattern in the Payra River. The b value of LLR also indicates the same growth pattern. The estimated a3.0 value was 0.007, indicating the fish has an elongated body profile. Among the four types of condition factors, KF is the best‐suited tool for evaluating the well‐being of L. guntea in the Payra River. Additionally, WR exhibited very significant divergence from 100 (p < .0001), designating an imbalanced habitat for L. guntea. The calculated Lm, Mw and Lopt values were 6.54 (~6.5 cm) in TL, 1.16/year and 7.46 cm TL for L. guntea in the Payra River, respectively. Thus, the results of the present study could be used in the future for improved management of this species in Payra River, as well as for linking ecosystems.

Population Dynamics of the Caroun Croaker Johnius carouna (Cuvier, 1830) in Coastal Fishing Ground in the Middle Gulf of Thailand

The stock status of coastal species is currently of high concern among the people. In the Gulf of Thailand, Croakers are important economic species commonly found in the coastal fishing ground, especially in Nakhon Si Thammarat province. The population dynamics of the Caroun croaker, Johnius carouna (Cuvier, 1830), was investigated using length-frequency distribution data collected from February 2019 to January 2020. The length-weight relationship equation suggested that J. carouna is isometric growth. The asymptotic total length (L∞) and curvature growth (K) were 22.28 cm and 0.72 year-1, respectively. Based on L∞ and K, the total mortality rate during the study period was estimated at 3.66 year-1; natural mortality and fishing mortality rates were estimated at 1.62 and 1.74 year-1, respectively. While biological data revealed that matured size was 15.3 cm, the fishing data suggested that the average catch size (15.12 cm) was slightly smaller than the matured size. The exploitation rate was 0.52 year-1. The result from this research suggests that current fishing pressure is slightly high. This study suggested that increasing catch size by increasing mesh size of gillnets seems to be a better solution to improve J. carouna stock in Thasala fishing ground in the future. HIGHLIGHTS The first report onJohnius carouna fishery biology in coastal fishing ground in the middle Gulf of Thailand Johniuscarouna is an isometric fish Matured size of Johniuscarouna is 15.3 cm Current fishing pressure on Johniuscarouna is slightly high GRAPHICAL ABSTRACT

The Biological Aspects of the Main Targets of Troll Line at Palabuhanratu Fishing Port, Indonesia

The biological aspect is a piece of basic information that is commonly presented in assessing the level of environmental friendliness of fishing gear or fishing vessel. This study was conducted to analyze the biological aspects of the main catch of the troll line at the Palabuhanratu Fishing Port, Sukabumi, Indonesia. The biological aspects analyzed consisted of length frequency distribution, length-weight relationship, to the average feasibility status of the caught target fish. There were three main target commodities for fishing from the troll line that was identified during the research activity, namely yellowfin tuna (Thunnus albacares), skipjack tuna (Katsuwonus pelamis), and frigate tuna (Auxis thazard). A total of 14 troll line fleets were obtained as a source of research data based on the accidental sampling method. The total number of 1404 fish consisting of 480 yellowfin tuna, 475 skipjack tuna, and 449 frigate tuna were obtained as research data objects. The stratified random sampling method was used in determining the observed sample fish data. Yellowfin tuna were distributed at size 29 – 148 cm, skipjack tuna at size 29 – 88 cm, and frigate tuna at size 23 – 82 cm. Analysis of the length-weight relationship showed a negative allometric growth pattern in the three main fishing target commodities. The analysis of the feasibility of the average fish caught based on compared of L50% to ½ L∞ shows that the average size of tuna and frigate tuna caught is undersize for catching, while the average skipjack caught has reached a legal size. The results of this study indicate that there is a need for a review of the use of fishing hooks in the fishing activity of the troll line fishing fleet. Increasing the hook size can be used to avoid catching fish that are at a size that is not suitable for catching.

Gillnet Selectivity on the Narrow-barred Spanish Mackerel (Scomberomorus commerson) Fishery in Pangandaran Waters

Analyzing the selectivity of gillnet fishing gear using two different mesh sizes, namely 3.5 and 4 inches. Gillnets of these mesh sizes are commonly used by fishermen in Fish Landing Base (PPI) Cikidang, Pangandaran Regency, West Jawa. A total of 8 fishing trips were conducted at the coastal waters around PPI Cikidang, Pangandaran Regency, West Java from August 2018 to January 2019 using gillnet fishing gear As for each trip, 2-3 times the operation of the tool is carried out. The operation of the fishing gear is carried out with the help of vessels measuring 2-3 Gross Tonnage (GT). The catch obtained was differentiated based on the main catch and bycatch and the amount is calculated for analysis of the proportion of the catch. Mackerel (Scomberomorus commerson) is caught as the main catch, the fork length was measured for analysis of the length frequency distribution and selectivity curves. The operation of gillnets with a mesh size of 3.5 inches obtained a higher proportion of bycatch compared to gillnets with a mesh size of 4 inches. In addition, the length distribution of mackerel caught by gillnets with a mesh size of 3,5 inches is smaller (27-49 cm FL) compared to a mesh size of 4 inches (40-55 cm FL). Based on the distribution of length distribution, gillnets with a mesh size of 3.5 inches are more dominant in catching mackerel in a smaller size class interval than gillnets with a mesh size of 4 inches. Meanwhile, based on the selectivity curve for the length of mackerel with a 50% chance of being caught, it shows that gillnets with a mesh size of 3.5 or 4 inches are selective in catching mackerel, this is because the chances of catching fish at more than L50 are high.

Güneydoğu Karadeniz’de dağılım gösteren kahküllü horozbina balığı Parablennius tentacularis (Brünnich, 1768)’de yaş tahmini ve en uygun büyüme modelinin seçimi

By the study's coverage, 522 individuals of tentacled blenny (Parablennius tentacularis (Brünnich, 1768)), were caught with the bottom trawl operations (commercial fisheries and scientific field surveys) between May 2010 and March 2012 from the southeastern Black Sea. The size distribution range of the sample varied between 4.8-10.8 cm. The difference between sex length (K-S test, Z=3.729, P=0.000) and weight frequency distributions (K-S test, Z=3.605, P=0.000) was found to be statistically significant. The length-weight relationship models were defined as isometric with W = 0.009L3.034 in male individuals and positive allometric with W = 0.006L3.226 in female individuals. Otolith and vertebra samples were compared for the selection of the most accurate hard structure that can be used to determine the age. Otolith was chosen as the most suitable hard structure. The current data set was used to predict the best growth model. For this purpose, the growth parameters were estimated with the widely used von Bertalanffy, Gompertz and Logistic growth functions. Akaike's Information Criterion (AIC), Lmak./L∞ ratio, and R2 criteria were used to select the most accurate growth models established through these functions. Model averaged parameters were calculated with multi-model inference (MMI): L'∞ = 15.091 cm, S.E. (L'∞) = 3.966, K'= 0.232 year-1, S.E. (K') = 0.122.

ESTIMATES OF LENGTH-BASED POPULATION PARAMETERS OF SKIPJACK TUNA (KATSUWONUS PELAMIS, LINNAEUS 1798) FROM A POLE & LINE FISHERY IN MAUMERE-SIKKA, INDONESIA

Several population parameters of skipjack tuna (Katsuwonus pelamis) taken by pole and line gear from Maumere Waters from March 2017 to February 2018 were analyzed. A total of 2,194 skipjack tuna was sampled randomly. Fishing activities were carried out around FADs (Fish Aggregating Devices) and free fish shoal. Observers and enumerators collected data from several landing sites and by direct on-board observations. This study aims to provide length-frequency distribution by season, estimate growth mortality parameters, and estimate stock exploitation rate using FISAT software. The results showed that the total catch was dominated by skipjack tuna; up to 80% with the CPUE of 30.8 kg/person/trip, and the skipjack tuna’s length distribution ranged from 26 to 69 cm FL. Length at first capture (Lc) was 34.71 cm FL, and immature fish dominated the total catch with 53%, indicating growth overfishing. The calculated von Bertalanffy growth (VBG) parameters were L= 70.35 cm, K = 0.55 yr-1, and t0 = -0.39 yr. Natural mortality (M) was estimated to be 0.92 and fishing mortality (F) was 0.91. The mean longevity of skipjack tuna is estimated to be 3.2 years, with an exploitation rate (E) of 0.50. Sustainable exploitation of skipjack tuna determined from this analysis could be developed with an Emax of 0.73. There is a focus on reducing the catch of immature fish through various methods that include changing the fishing target area from FADs to fishing on natural fish schools and using gear modifications such as larger-sized (lower number) hooks.

Morphology character and length-weight relationship of Goblinfish (Neovespicula depressifrons) Tetraogidae in Percut Sei Tuan Coastal, North Sumatera, Indonesia

The research was conducted in Percut Sei Tuan Aquatic with goblinfish (Neovespicula depressifrons) as the main object. Goblinfish was caught at a brackish aquatic which is mangroves are grown. This study aimed to analyse the relationship between weight-length, growth pattern, length-frequency distribution, and condition factors of goblin fish. Danish seines with mesh size net of 1 inch, ½ inch, and ¼ inch was used for fishing. After the fish caught, then measured the total length and weighed, measurements were conducted in the laboratory. The total length of fish caught is in the range of 24-65 mm and a weight of 0.2 - 3 g. The resulting group size consisted of 7 groups with class intervals of 42-47 mm is the mode group size. From the analysis of the length-weight relationship, the constant value of b = 0.972 and the value of the condition factor ranges from 0.90 to 1.37 with an average value of CF > 1.

Amending survey design to improve statistical inferences: Monitoring recruitment of juvenile reef fish in the eastern Gulf of Mexico

Many species of interest to management and conservation remain data-limited, and the data that are available are often unable to produce statistically reliable population trends. We examined 10 years of juvenile reef fish catch data from two gear-specific, fishery-independent surveys in the eastern Gulf of Mexico to assess our ability 1) to characterize population trends for various reef species sampled using haul seines or otter trawls and 2) to amend our survey, as logistics would allow, to improve those characterizations. Species richness, catch-per-unit-effort, and length-frequency distributions were generally similar between gear types, suggesting a single survey (i.e., one gear type) may be sufficient. Simulation-based power analyses for the reef fish species indicated that overall, otter trawl data provided greater power for detecting trends over a 10-year period (41–75 % probability to detect a 50 % change in abundance) than haul seine data (27–52 %). Likewise, otter trawl data provided greater power for detecting trends from one year to the next (22–53 % probability to detect a 50 % change in abundance in one year) than haul seine data (15–33 %). Simplifying data collection from two surveys to a single, trawl-only survey (and approximately doubling the number of trawl tows) was more efficient, more effective, and more powerful (64–91 % for the amended design with more tows) in detecting abundance trends. Furthermore, by increasing sample size but retaining all other design elements, the data collected during the trawl survey before and after the change remain comparable; the time series was not interrupted. These changes increase our confidence in estimating population trends, predicting productivity, and informing management and conservation decisions.

“The Road not taken” statistically taken: A probabilistic analysis of Frost’s poem

“The Road Not Taken” is an exemplary poem composed by Robert Frost in 1916. The focal point of the paper is a careful statistical study of this poem intensifying several features such as: Whether the number of words per line follows uniform distribution or not. Studying the frequency distribution of word length and fitting a suitable probability model. Do the number of vowels follow a binomial or a quasi binomial model? Are the number of letters per line uniformly distributed? Computing the empirical probability of each alphabet in the poem. Analysis of rhythm in the poem. Analysis of parts of speech used in the poem. From the statistical analysis it is found that a Zero truncated Poisson distribution is a good fit for the frequency distribution of word length. The number of words per line may be taken as distributed uniformly in the poem which is tested by Chi Square goodness of fit test. Binomial distribution turns out to be a good fit for the number of vowels per stanza in the poem. The number of letters per line are distributed uniformly in the poem which is also tested by Chi Square goodness of fit test. The poem is following the rhythmic scheme abaab cdccd efeef ghggh. The number of words between two successive rhythmic words can be trichohotomized. The proportion of the first 13 letters (A to M) is more and significantly different as compared to that of the last 13 letters (N to Z). Finally verb is the maximum used part of speech in the poem.

Growth, Condition, Maturity and Mortality of the Dwarf Gourami, Trichogaster lalius (Hamilton, 1822) in a Wetland Ecosystem (Beel Dakatia), Southwestern Bangladesh

The dwarf gourami, Trichogaster lalius, is a low-cost freshwater edible fish for the people of South Asian countries containing a variety of essential nutrients. The first wide-ranging explanation on the population parameters specifically; length-frequency distribution (LFD), length-weight relationships (LWRs), length-length relationship (LLR), form factor (a3.0), condition factors (allometric, KA; Fulton’s, KF; relative, KR; relative weight, WR), size at first sexual maturity (Lm) and natural mortality (Mw) of T. lalius were estimated. 768 specimens were collected over one calendar year (March 2019 to February 2020) from a wetland ecosystem named Beel Dakatia, Khulna, southwestern Bangladesh through various traditional fishing gears. Lengths (in cm) and weight (in g) were assessed through a wooden fitted measuring scale and digital balance with accuracy 0.1 cm and 0.01g, respectively. In the current study, the total length ranged from 2.6-9.9 cm while the bodyweight ranged from 0.63-23.80 g for T. lalius. The TL size for classes of 7.00 to 7.99 and 8.00 to 8.99 cm indicated numerically prominent groups. Moreover, the calculated allometric coefficient (b) of LWRs represented a negative allometric growth pattern (b<3.00) for T. lalius in the Beel Dakatia. Noticeably, the a3.0 was 0.015 signifying that the fish is fusiform in shape. KF is the best-suited tool to assess the well-being of T. lalius among the four types of condition factors. According to Wilcoxson signed-rank test, the WR revealed significantly dissimilarities from 100 (P<0.0001), signifying the unbalanced territory for T. lalius. Moreover, the estimated Lm was 5.91 (~6.0) cm TL and Mw was 1.28 year-1 in the Beel Dakatia, southwestern Bangladesh. Finally, the knowledge about the biological aspects of T. lalius may be used for improved management tools in the future.

Age, growth and mortality of the yellowmouth barracuda Sphyraena viridensis (Sphyraenidae) from eastern coasts of Algeria

AbstractAge and growth of the yellowmouth barracuda Sphyraena viridensis (Cuvier, 1829) was examined in 698 individuals (184 &lt; TL (mm) &lt; 1210; 25 &lt; TW (g) &lt; 7125), sampled monthly from commercial catches in eastern coasts of Algeria between January 2007 and January 2008. Marginal increment analysis of 159 sectioned sagittal otoliths combined with information derived from length–frequency distribution showed that annulus formation occurs between June and August. Maximum observed age of males and females is 14 and 13 years respectively. Back calculations of total length-at-age were used to fit the data to the Bertalanffy growth model: TL = 1113(1 – e−0.165(t+2.251)) in males and TL = 958.3 (1 – e−0.247(t+1.422)) in females. The coefficient of allometry of the length weight relationship is 3.02 and 2.99 in males and females, respectively. Growth performance index Ø = 3.33. Natural mortality (M) was estimated as 0.45 year−1, fishing mortality (F) was 0.06 year−1and the exploitation rate (E) was 0.11.

Population structure and shell dimension of the invasive veined whelk (Rapana venosa)

The veined whelk (Rapana venosa) is a widely known invasive species in the Black Sea. This species exerts negative impacts on the Black Sea ecosystem including destruction of bivalve, mussel and oyster populations. This study aimed to examine population structure using the length-frequency distribution and shell dimensions of R. venosa, collected from the Black Sea. A total of 506 specimens were collected from the Trabzon Coast and classified into 6 age groups using the Bhattacharya method. The Von-Bertalanffy growth parameters were calculated as L∞ = 10.29 cm, k = 0.09, t0 = 1.25 yr–1. The mortality and exploitation rates were estimated as total mortality Z = 0.51 yr–1, fishing mortality F = 0.31 yr–1, annual mortality M = 0.20 yr–1 and exploitation rate E = 0.60 yr–1. This study will help understanding the growth of R. venosa and its management.

Length-Weight Relationship, Sex Ratio and Condition Factor of Merlangius merlangus (Linnaeus, 1758) From the Sea of Marmara, Turkey

In this study, some biological properties of Merlangius merlangus (Linnaeus, 1758) were examined. In this context, relationship of length-weight, distribution of length-frequency, sex ratios and condition factors were examined. A total of 303 individuals were taken by random sampling from fishing vessels (beam trawl) in the Sea of Marmara. Minimum length and weight values of all sample individuals was found 10.0 cm and 6.6 g, maximum length 41.2 cm and 535 g was found. The average length was found 17.15±0.49 cm and the average weight was 47.03±7.57 g. Length-weight relationship for all samples as W=0.0044TL3.1777 regression coefficient r2=0.98 was determined. Growth type, positive allometric was determined for all samples and both sexes (b˃3; P˂0.05). The sex ratio (F:M) was calculated as 1:1.27. The mean values of condition factor (K) were calculated as 0.729±0.089, 0.733±0.091 and 0.737±0.081 for male, female and combined sex respectively. There are no significant differences between male and female (P˃0.05).