Length Classes Research Articles

The biggest or the most abundant? Predation of the Black Drum Pogonias cromis (Perciformes, Sciaenidae) on benthic organisms in southern Brazil

Predators that consume larger prey acquire a greater net return of energy per individual, even though they are less abundant. The objective of this work is to analyze the feeding biology of Pogonias cromis in southern Brazil, in order to test for the occurrence of ontogenetic changes in diet as fish reach larger sizes, by consuming larger prey as they grow. Between August 2014 and May 2016, 347 specimens were collected from catches of the fishing fleet that operate in the Patos lagoon estuary and in the adjacent marine area of Cassino beach, that use artisanal fishing gillnets. The prey-specific relative importance index, food overlap, niche breadth and prey length preference were calculated for three length classes, class 1 (27.8–48.73 cm), class 2 (48.73–69.66 cm) and class 3 (69.66–90.60 cm). A total of 13 food items (6 species of crustaceans, 5 species of mollusks, fish fragments and non-animal fragments) were identified, where two species of mollusks (Heleobia australis and Erodona mactroides) represented 90.49% of the diet. The overlap index was moderate between classes 1 and 2, high between 2 and 3 and moderate between 1 and 3. There was a low niche breadth at the population level and for each length class. There were no significant differences in the length of prey consumed among classes. The data obtained here indicates that P. cromis can be classified as a predator specialized in mollusks, with low tendency to ontogenetic changes in southern Brazil. Considering information from the population of P. cromis from Argentina, it can be inferred that the species in the waters of southern South America is a benthic predator adapted to local conditions.

Predicting Fishing Footprint of Trawlers From Environmental and Fleet Data: An Application of Artificial Neural Networks

The increasing use of tracking devices, such as the Vessel Monitoring System and the Automatic Identification System, have allowed, in the last decade, detailed spatial and temporal analyses of fishing footprints and of their effects on environments and resources. Nevertheless, tracking devices usually allow monitoring of the largest length classes composing different fleets, whereas fishing vessels below a regulatory threshold (i.e., 15 m in length-over-all) are not mandatorily equipped with these tools. This issue is critical, since 36% of the vessels in the EU fleets belong to these “hidden” length classes. In this study, a model (namely, a cascaded multilayer perceptron network) is devised to predict the annual fishing footprints of vessels without tracking devices. This model uses information about fleet structures, environmental characteristics, human activities, and fishing effort patterns of vessels equipped with tracking devices. Furthermore, the model is able to take into account the interactions between different components of the fleets (e.g., fleet segments), which are characterized by different operating ranges and compete for the same marine space. The model shows good predictive performance and allows the extension of spatial analyses of fishing footprints to the relevant, although still unexplored, fleet segments.

Population dynamics of the Brown mussel Perna perna at a Rocky beach near Cape Coast, Ghana

AbstractThe brown mussel, Perna perna, is an ecologically important species which has a great potential for aquaculture in Ghana. Though it is harvested from the wild for consumption locally, there is no information on its population parameters to guide its management and subsequent culturing. The species inhabiting Iture rocky beach near Cape Coast (Ghana) was therefore investigated to elucidate its growth and other population parameters. Specimens had shell length ranging from 5.00 to 78.0 mm, a modal shell length class of 35.0–39.9 mm, and exhibited negative allometric growth. The asymptotic length (L∞), growth coefficient (K), and growth performance index (Φ') were 80.10 mm, 0.49 per year, and 3.49, respectively. The recruitment pattern showed that P. perna has year‐round recruitment with a single peak between April and July. Total mortality (Z) was estimated at 2.79 per year, while natural mortality (M) and fishing mortality (F) were 0.87 and 1.92 per year, respectively. The calculated exploitation level of the population (E = 0.69) suggests possible overfishing of the mussels at Iture rocky beach. These results could serve as baseline information for management of the mussel population in Ghana.

Heterogeneous sensor-based condition monitoring in directed energy deposition

The objective of this work is to detect in situ the occurrence of lack-of-fusion defects in titanium alloy (Ti-6Al-4 V) parts made using directed energy deposition (DED) additive manufacturing (AM). We use data from two types of in-process sensors, namely, a spectrometer and an optical camera which are integrated into an Optomec MR-7 DED machine. Both sensors are focused on capturing the dynamic phenomena around the melt pool region. To detect lack-of-fusion defects, we fuse (combine) the data from the in-process sensors invoking the concept of Kronecker product of graphs. Subsequently, we use the features derived from the graph Kronecker product as inputs to a machine learning algorithm to predict the severity (class or level) of average length of lack-of-fusion defects within a layer, which is obtained from offline X-ray computed tomography of the test parts. We demonstrate that the severity of lack-of-fusion defects is classified with statistical fidelity (F-score) close to 85% for a two-level classification scenario, and approximately 70% for a three-level classification scenario. Accordingly, this work demonstrates the use of heterogeneous in-process sensing and online data analytics for in situ detection of defects in DED metal AM process.

Biological Aspects, Catch and Length Distribution of African Catfish, Clarias gariepinus and Common Carp, Cyprinus Carpio in in Lake Lugo, South Wollo, Ethiopia

Determining biological parameters such as length to weight relationship, sex ratio and size at first maturity of threatened fishes give good information on their growth performance and help manage and conserve fish populations in their natural water bodies. In this study, some biological parameters were reported for Clarias gariepinus and Cyprinus carpio. Samples were taken at monthly intervals from October 2013 to September 2017 in Lake Lugo, South Wollo, Ethiopia. The objective of the study was to determine length to weight relationships, length class frequency, sex ratio and size at first maturity of the fishes. Total length (TL) of the species was measured to the nearest 0.1 cm and total body weight (TW) to the nearest 1 g. The physico-chemical parameters were also measured: transparency by using secchi disk, conductivity by Wagtach International conductivity meter and pH by pH meter. The results showed that the parameters were within the permissible limits except the pH level at Gedam Sefar sampling site. A total of 672 fish specimens were collected. Length (cm) to weight (g) relationship for C. gariepinus was sketched as: TW = 0.015TL2.8, n = 81, r2 = 0.901 and for C. carpio as: TW = 0.018TL2.85, n = 591, r2 = 0.926, which, in both cases, showed a curvilinear relationship, signifying the fishes followed negative allometric growth. The sex ratio between males to females showed significant difference (C. gariepinus: χ2 = 4.46, P<0.05; C. carpio: χ2 = 12.0, P<0.05). Size at first sexual maturity (L50) for C. gariepinus was 31.7 cm for females and 31.1 cm for males, while L50 for C. carpio was 19.2 cm for females and 19.3 cm for males.

Volume recovery and estimation of commercial volumes of Okan (Cylicodiscus gabunensis Harms) in southern Cameroon

The objective of this study was to quantify the volume of residues and develop volume equations for estimation of commercial outside-bark volumes of Okan (Cylicodiscus gabunensis) at different logging stages. Two hundred and five stems with diameter at breast height (DBH) varying between 65 and 167 cm were cut and scaled (by successive logs) and followed at forest management unit 09 004b in South Cameroon. The relationships between the scaled volumes and the measured dendrometric variables were established using weighted regressions. The largest proportion (>63%) of the total volume of discarded waste was observed at the stump. Modelling the proportion of stem residues, although resulting in a low R2 value, was best described by considering log length and quality class. Commercial volumes were estimated using DBH, the proportion of waste, grade quality and commercial length. Although difficult to estimate, commercial length offers better results compared with the use of grade quality. These results can contribute to better management of Okan’s commercial timber stocks in South Cameroon.

Effects of water temperature and prey density on recent growth of chub mackerel Scomber japonicus larvae and juveniles along the Pacific coast of Boso–Kashimanada

The effects of temperature and prey density on the recent growth rate (RGR) of chub mackerel, Scomber japonicus, were examined. Scomber spp. larvae and juveniles were collected along the Boso–Kashimanada Pacific coast in Japan between March and July in 2015 and 2016. Larvae and juveniles identified as S. japonicus using DNA were subjected to stomach-content and otolith-increment analyses. The effects of temperature and prey density on RGR were analyzed using a generalized linear mixed model (GLMM), which showed that temperature positively affected the RGR of larvae in the body length (BL) classes 11 mm classes and effects of prey density on RGR for larger (> 11 mm) larvae and juveniles were stronger than those for smaller (< 9 mm) larvae. S. japonicus larvae transform into juveniles at around 12 mm BL, and the increased feed demands of juveniles likely lead to prey-density-dependent growth. The otolith increment widths of larvae and juveniles were significantly narrower than those during the same stages in 1-year-old S. japonicus collected from purse seine fisheries operated in the Joban or Kashimanada areas, suggesting growth-dependent mortality.

Reproductive biology of the protandric hermaphrodite fat snook Centropomus parallelus Poey 1860 in a tropical estuary, northeastern Brazil

ABSTRACTThe aim of the present study was to analyze the reproductive aspects of the fat snook, Centropomus parallelus, in a tropical estuary. During the study period, 187 specimens were collected, including 73 females and 114 males. The length at first sexual maturity was estimated to be 224 mm for the females and 141 mm for the males. An extensive reproductive period, January to August, was observed for the females based on the gonadosomatic index. For the males, the highest values were from July to October. Sexual segregation was observed in length classes, with predominance of males and females in the smaller and larger sizes, respectively. This pattern, observed in protandric hermaphrodites, has been confirmed with the identification of an individual in sexual transition. The average relative fecundity was 14,260 oocytes. The average absolute fecundity was 491,036 oocytes/female, and the average size of the vitellogenic oocytes was 435 µm. Management actions are suggested for better conservation of the species.

Simple nonlethal identification criteria for two endangered freshwater pearl mussels, Margaritifera laevis and Margaritifera togakushiensis, in Hokkaido, northern Japan

AbstractSpecies identification is a fundamental process for ecological studies and conservation practices, and simple nonlethal identification criteria are important for endangered species. This study developed species identification criteria for two endangered freshwater pearl mussels (Margaritifera laevis and Margaritifera togakushiensis) based on linear discriminant functions (LDFs) that were established considering intraspecific regional morphological differences from sites at Hokkaido, northern Japan. We collected a total of 1,110 mussels from 52 rivers across 32 watersheds in two geographical regions (east and west). Shell morphologies (length, height, and width) of the collected mussels were measured, followed by species identification with gel electrophoresis banding patterns of 16S rRNA polymerase chain reaction products. LDFs were constructed for two size classes (≥40 mm and &lt; 40 mm) using forward stepwise procedures to determine key morphological differences between the two species and consideration of whether regional morphological differences improved identification accuracies. The LDFs revealed that the morphologies of the two species were clearly distinguished by the relationship between height and length for both size classes. Region‐specific LDFs produced better identification accuracies. Regardless of region, the maximum length of M. laevis exceeded 100 mm, whereas all M. togakushiensis were &lt; 100 mm in length. Identification accuracies of the established LDFs were high for each of the five length classes (0–20 mm, 20–40 mm, 40–60 mm, 60–80 mm, and 80–100 mm) with 85–96% (mean: 92%) accuracy in the east and 67–96% (mean: 80%) in the west. These criteria for species identification will progress future ecological studies and conservation practices for freshwater mussels.

Technological level of high power wheel tractors

The aim of the work is a comparative assessment of the technological level of high-power wheeled tractors in the natural-industrial conditions of the Eastern agrozone of the Siberian Federal District. As the main criterion for adaptation to natural production conditions, when forming models and algorithms for assessing the technological level of Russian-made production tractors of different configuration, we used a generalized net performance indicator corresponding to the minimum reduced costs for different classes of rut and groups of tillage operations with specific characteristics of specific traction resistance of working machines and the nominal values of technological speed. According to the simulation results, rational traction modes were defined, limited by 7-15% skidding of propulsions and the corresponding change ranges and axle distribution of wheeled 4K4b tractors of different configurations. For the prevailing class of rut length more than 1000 m, the required tractor power, taking into account the employment in operations of different groups, was 260 kW on single wheels and 250 kW doubled with an operating weight of 14.64-17.60 t and 15.70-18.38 t respectively. With an average for the agrozone, the rut length class of 600–1000 m, the optimum values of the mass-energy parameters of the tractor are at the level of 0.80–0.81 from those indicated. According to the criterion of the technological level in the natural production conditions of agrozones with a rut length of more than 1000 m, the Kirovets tractors of models K-740P, K-742C and K-742P with an operating capacity of 284-298 kW on single wheels and tractor RSM-2375 (240 kW) on dual are mostly efficient (Kэ ≥ 0, 950). Doubling the tractor wheels increases productivity by 5-6% and fuel efficiency of the aggregates up to 14% with a two-fold decrease in pressure on the soil.

Analysis of a Length-Structured Density-Dependent Model for Fish.

We present a length-structured matrix model for fish populations in which the probability that a fish grows into the next length class is a decreasing nonlinear function of the total biomass of the population. We present mathematical results classifying the dynamics that this density-dependent model predicts. We illustrate these results with numerical simulations for an invasive white perch population and show how the mathematical results can be used to predict the persistence and/or boundedness of the population as well as an equilibrium structure that is dominated by small fish. We illustrate the results with management recommendations for an invasive white perch population.

Growth and mortality parameters of the black-chinned tilapia Sarotherodon melanotheron melanotheron (Pisces: Cichlidae) in a small lagoon in the Central Region of Ghana

This study quantified growth, mortality, and exploitation rate of the black-chinned tilapia (Sarotherodon melanotheron melanotheron) population in Etsir Lagoon, a small brackish waterbody at Abandze (5°11′ N, 1°5′ W) in the Central Region of Ghana for management of the stock. Fish samples were collected monthly between April 2014 and March 2015, and specimens measured 3.9–13.8 cm SL with a mode in the 7.0–7.9 cm length class. Analysis of the length-frequency data of 861 specimens using the ELEFAN method indicated a growth constant (K) of 0.93 yr−1, and asymptotic length (L∞) of 14.3 cm SL for the population. The short lifespan (tmax = 3.2 years) determined for the species and estimated growth parameters suggest stunting in the population, as in other brackish water populations in Ghana. The total mortality (Z), natural mortality (M), and fishing mortality (F) coefficients: 5.09 yr−1, 2.15 yr–1 and 2.95 yr−1, respectively, indicate fishing as a major contributor to total mortality. The calculated exploitation rate (E = 0.58) of the population suggests overexploitation of the stock, however, the all-year- round recruitment in the population probably ensures production at levels that compensate for its relatively high exploitation rate.

The annual reproductive cycle and sex inversion of the Picnic seabream,Acanthopagrus berda(Forsskål 1775) from Indian waters: Histological and morphometric description

The annual reproductive cycle of picnic seabream, Acanthopagrus berda (Forsskal, 1775), one of the potential aquaculture candidate from estuarine waters of Calicut, Kerala (India) was studied. Based on the morphological and histological studies, the ovotestes of A. berda were classified as active male, active female, inactive male, inactive female, transitional and undifferentiated. Histological observation of transitional gonads showed signs of degeneration in the testicular lobe, proliferation of connective tissue and empty sperm ducts indicating protandrous hermaphroditism in A. berda. Ovary was classified into seven maturity stages (virgin, developing virgin, developing, maturing, mature, running, spent) and testis into five maturity stages (resting, maturing, mature, running, spent). Gonadal development in A. berda indicated resting phase (February–July), pre‐spawning phase (March–August) and spawning phase (August–December). Inactive (24.6%) and active males (21.6%) were observed as dominant in smaller length classes (140–250 mm TL), whereas inactive (18%) and active females (51%) were observed as dominant in larger length classes (251–450 mm TL). Few primary females (28.1%) were observed in smaller (below 250 mm TL) and few primary males (28.5%) were observed in larger length classes (above 250 mm TL). From the present study, it can be concluded that in A. berda, most of the individuals function first as males and then change sex to female, but few continue to function as either male or female throughout their lifespan indicating digynous protandrous hermaphroditism.

Comparative Morphometry of the Genus Thais from Nembe, Bakana and Calabar

Aim: Morphometry of Thais spp found in the Niger Delta Mangrove vegetation of Bakana, Calabar and Nembe were examined and compared.&#x0D; Study Design: The study is a cross-sectional observational study&#x0D; Place and Duration of Study: The study ws carried out in Bakana, Calabar and Nembe during a period of six months(January to June, 2018).&#x0D; Methodology: A total of 600 specimens (100 specimens per month) were collected during a period of six months (January to June 2018) from the three sampling communities. Three different species were identified namely: Thais coronata, Thais haemastoma and Thais lacera. Shell dimensions were measured to the nearest millimeter using Vernier calipers and weighed, to get the morphometric Characteristics: Whorl Diameter (WD), Shell length (SL), Shell width (SW), Body whorl length (BWL), Aperture length (AL), Aperture Width (AW) Shell Breadth (SB), and Animal Weight (AW). Number of whorls, number of primary spiral cord on the body and number of ridges or teeth inside of outer tip of the aperture were counted.&#x0D; Results: The disparity between the morphometric traits across the different species identified were minimal as most of the species had similar values of morphometric traits. However, differences can be identified using their colour; thais coronata (dirty light grey), T haemastoma (light grey), and T lacera (plane grey). The Three (3) species had a modal length class of 3.5cm to 4.5cm. Thais coronata and Thais lacera had a modal weight class of 9-11grams while Thais haemastoma had a modal weight class of 6-7grams. It was observed with the aid of length/weight relationship that the found in all study.&#x0D; Conclusion: It was observed with the aid of length/weight relationship that the Thais specimen found in all study locations exhibited a very weak linear relationship with very low R2 values across locations. The exponent b of Thais coronata and Thais haemastoma and T. lacera across the three study locations indicate a negative allometric growth pattern. The Month of April for samples collected from Nembe had the highest condition factor for the three (3) species. T. coronata (4.4), T. lacera (6.38) and T haemastoma (5.5).

Documentation of Freshwater Mussels (Unionidae) in the Diet of Round Gobies (Neogobius melanostomus) within the French Creek Watershed, Pennsylvania

The round goby (Neogobius melanostomus) was discovered in 2013 in the French Creek (Allegheny River Drainage) watershed and is the first documented invasion outside of the Lake Erie basin in Pennsylvania. The round goby throughout the Laurentian Great Lakes is known to eat dressenid mussels (Dreissenidae), but consumption of either dressenids or native mussels (Unionidae) in tributaries to Lake Erie is minimal based on low populations of any bivalves. The French Creek watershed, on the other hand, harbors 29 species of native freshwater mussels as well as introduced fingernail clams (Sphaeriidae; Corbicula fluminea). The objectives of this study were to document the diet of round gobies in the French Creek watershed to determine whether consumption of native freshwater mussels was occurring. Round gobies were collected in the summer months (May–Sept.) of 2016 via kick seine in four locations, dissected, and their stomach contents identified to lowest possible taxa. We separated the gobies into categories based on length classes, in order to determine if diet changed with increased size and age. Unionid mussels were consumed by all length classes, particularly in length class one (30–44 mm), but diet shifted to a dominance of sphaeriids in length class four (≥75 mm). Round gobies also consumed benthic aquatic insects, a large percentage of which were chironomids (greater than 24% in all size classes). This is the first documentation of unionid consumption by the round goby in Pennsylvania that poses possible threats to native mussels in the French Creek watershed.

Reproductive biology of the armored catfish Neoplecostomus microps in a coastal Atlantic Forest stream, southeastern Brazil

This work aims to analyze reproductive attributes of the species Neoplecostomus microps (Steindachner, 1877), a well-known species of the catfish family Loricariidae but little con - templated in ecological studies. We describe the reproductive behavior of the species and compare the patterns identified in 2 different basins. The specimens (117 males and 102 females), collected in the Macae River, did not present a bias in sex ratio during the year. In the largest length classes, males predominated and attained earlier maturity than females. The length−weight relationship showed positive allometric growth for both sexes. The variation of the gonadosomatic index and frequency of maturation stages indicated a reproductive period of 4 to 6 mo, starting in September and reaching a peak in November. The mean absolute fecundity was 43.83 (SD = 7.62) oocytes, ranging from 32 to 55 oocytes. The frequency distribution of oocyte diameter of mature ovaries revealed 3 clutches, suggesting batch spawning. A prolonged reproductive period, low fecundity, large eggs, possible parental care, and repeated spawns recorded for N. microps suggest a strategy that maximizes parental fitness. The population structure and reproductive characteristics of this species indicate a tendency toward equilibrium. The early maturation in females in the Macae River population may favor a more rapid replacement of juveniles in the population as a response to the unstable environmental conditions that the population experiences in the rainy season.

Productivity of logging large diameter logs and long logs during final cutting in a mountain forest in Japan

ABSTRACTA large portion of planted forests in Japan have recently reached maturity. These trees have grown larger than previous stands, and are more difficult to log using current techniques. This study aimed to develop an improved logging system for logs with relatively larger diameters and lengths in Japan. In a moderate-slope mountain forest in Toyama Prefecture, we evaluated the productivity of final cutting and compared the productivity of each log length class (4 m, 6 m, and 8 m) using both current-sized and larger-sized machine harvesting systems. Moreover, different felling techniques for large diameter trees were assessed using a mechanical wedge that is commonly used in central Europe. We found that felling using the mechanical wedge had additional safety benefits. Furthermore, the productivity using the larger machine system was higher than those using the current techniques and systems; however, the productivity was only marginally higher for larger machines across log length classes.

Population Dynamics and Exploitation Rate of Coral Grouper Plectropomus leopardus in the Sarappo Islands, Pangkep Regency, South Sulawesi

The coral grouper Plectropomus leopardus is a fish which plays important ecological roles in coral reef ecosystems. It is also a well-known and sought-after commodity in both local and export markets, leading to pressure on wild P. leopardus populations. The aim of this study was to describe the population dynamics and determine the exploitation rate of coral grouper (P. leopardus) populations in the Sarappo Islands, Pangkep Regency South Sulawesi, Indonesia. Coral grouper samples from Sarappo Island were caught using hand-line gear. Class length and weight data were analysed using the Bhattacharya method, von Bertalanffy model and Pauly empirical equation incorporated in the FiSAT II program to determine growth rate, mortality, and exploitation rate. The length frequency distribution of coral groupers sampled had length class means ranging from 20.0 cm to 57.1 cm. The 30.1 cm midpoint class had the highest catch frequency (162 fish) while the 57.1 cm class had the lowest frequency (3 fish). The length-weight relationship indicated an allometric growth pattern (b<3), with a growth coefficient (K) of 0.7. The total mortality (Z), natural mortality (M) and fishing mortality (F) were 3.03, 1.28, and 1.75, respectively, giving an exploitation rate E = 0.58 which exceeded the MSY limit (0.5). Coral grouper (P. leopardus) size structure was dominated by fish with immature gonad indices, increase in body length was faster than weight gain, fishing mortality was high, and the rate of exploitation exceeded the sustainable limit.

More Results on the Domination Number of Cartesian Product of Two Directed Cycles

Let γ ( D ) denote the domination number of a digraph D and let C m □ C n denote the Cartesian product of C m and C n , the directed cycles of length n ≥ m ≥ 3 . Liu et al. obtained the exact values of γ ( C m □ C n ) for m up to 6 [Domination number of Cartesian products of directed cycles, Inform. Process. Lett. 111 (2010) 36–39]. Shao et al. determined the exact values of γ ( C m □ C n ) for m = 6 , 7 [On the domination number of Cartesian product of two directed cycles, Journal of Applied Mathematics, Volume 2013, Article ID 619695]. Mollard obtained the exact values of γ ( C m □ C n ) for m = 3 k + 2 [M. Mollard, On domination of Cartesian product of directed cycles: Results for certain equivalence classes of lengths, Discuss. Math. Graph Theory 33(2) (2013) 387–394.]. In this paper, we extend the current known results on C m □ C n with m up to 21. Moreover, the exact values of γ ( C n □ C n ) with n up to 31 are determined.

SELECTIVITY OF Decapterus macarelus (SCAD) DRIFT GILLNET IN KAYELI BAY MALUKU BY KITAHARA’S METHOD

To study the gear selectivity on scad Decapterus macarelus fishing experiments using drift gill net with differents mesh sizes were conducted in Kayeli Bay Buru Island Maluku. To obtain data of fork length size composition, drift gillnets were operated at fish agregation devices along night time. The selectivity of drift gillnets for scad were estimated with Kitahara’s method. Mesh selectivity by a drift gillnet used for scad Decapterus macarelus shows a peaked curved with the efficiency at the peak of mesh selectivity increasing in proportion to the mesh size. The optimum size selectivity (fishing efficiency) of scad are ratio of 185 mm fork length class and 38 mm mesh size, 225 mm and 45 mm mesh size, and 255 mm and 51 mm mesh size.