Length Frequency Distributions Research Articles

Comparing indicators of recreational fishing in Port Phillip Bay, Australia, from 2008 to 2011 with variability from a background period (2003–07)

Understanding the effects of anthropogenic disturbances on marine environments that support recreational fisheries requires suitable monitoring data. Although catch rates are frequently considered to inform resource status for commercial fisheries, similar time series data are generally unavailable for recreational fisheries. This study is based on 9 years of data from boat-based recreational fishing surveys in Port Phillip Bay, Australia. Harvest rates and length distributions of the retained catches for three target species were statistically compared over 4 years following commencement of shipping channel dredging (2008–11) with variability from a background period (2003–07). Mean harvest rates were generally within historical ranges, with increases for snapper (Chrysophrys auratus) and King George whiting (Sillaginodes punctatus) and decreases for sand flathead (Platycephalus bassensis). Length–frequency distributions were not significantly different to the background period, except for increased mean length of snapper and King George whiting in 2011. This study demonstrates that data obtained from sampling recreational fishers can provide valuable information to monitor harvested resources and maintain social amenity for recreational fisheries during periods of anthropogenic disturbance. Trends in harvest rates from recreational fishing surveys may also complement catch rates from commercial fisheries for assessments of multisector fisheries or stand-alone assessments for recreational-only fisheries.

Relationships between fish and otolith dimensions of Pomatomus saltatrix (Linnaeus, 1766) (Perciformes: Pomatomidae) in southeastern Brazil

ABSTRACT The bluefish, Pomatomus saltatrix (Linnaeus, 1766), was used as a species-specific model to study morphometric relationships between otolith size and relative growth variables. Length-weight relationships between Otolith (Length-OL, Height-OH, and Weight-OW) and fish measurements (Total Length-TL and Total Weight-TW) were determined for fishes captured monthly during the year 2015 off the southeastern coast of Brazil. The ANCOVA and Kruskal-Wallis analysis did not indicate significant differences in the relative growth constants between sexes and length frequency distributions (p > 0.05). The condition factor also did not present significant differences between sexes, and right and left otolith measurements (p > 0.05). A total of 398 specimens were sampled: TL = 43.6-67.0 cm, TW = 365-2400 g, OL = 9.65-15.25 mm, OH = 3.65 - 5.45 mm and OW = 0.03-0.11 g. The LWR for grouped sexes was TW = 0.050TL2.55 and otoliths OW = 6.17E-05OL2.59. The best adjustments were TL vs OL (r2 = 0.90); OL vs OW (r2 = 0.90); TW vs OW (r2 = 0.81); and TW vs OL (r2 = 0.80). These results showed that such relationships are helpful tools for predicting the fish size and weight from otoliths, which may be used in food habits and paleontology studies, and other fisheries management applications.

Spatial distribution of Donax trunculus (Linnaeus, 1758) populations along the intertidal area of the Gulf of Cádiz (SW, Spain)

Spatial distribution of Donax trunculus (Linnaeus, 1758) populations along the intertidal area of the Gulf of Cádiz (SW, Spain)

Spatiotemporal distribution and growth pattern of Venus nux (Gmelin, 1791) in the Gulf of Cádiz (Southern Spain)

Spatiotemporal distribution and growth pattern of Venus nux (Gmelin, 1791) in the Gulf of Cádiz (Southern Spain)

Annual reproductive cycle and shell length frequency distribution of the clam Mactra chinensis in the dredge fishing ground in Mikawa Bay

Annual reproductive cycle and shell length frequency distribution of the clam <i>Mactra chinensis</i> in the dredge fishing ground in Mikawa Bay

Assessment of Technical and Economic Efficiencies of Gillnet Types with Different as against the Usual Same, Hanging Ratios at the Top and Down Ropes, Compared with a Standard Gillnet, In The Volta Lake, Ghana

The study was conducted at ten fishing sites, in Stratum VII of the Volta Lake, comparing the technical and economic performances of gillnet types with different as against the usual same, hanging ratios at the top and down ropes, with a standard gillnet of hanging ratio 0.5 at the top and down ropes. The objective was to determine whether gillnet types with different hanging ratios at the top and down ropes could be superior in enhancement of the performance of monofilament gillnets over the usual gillnet types with same hanging ratios at the top and down ropes, by determining principally the; fishing efficiency, cost efficiency and the index of economic efficiency of the net types, under the same fishing conditions. In April-June 2016, the depth of the fishing sites, the quantity and value of fish caught, and the costs of the fishing operations were determined; and in February 2017, the length frequency distribution of Oreochromis niloticus and Sarotherodon galileus, caught by the net types was recorded for differences. The results showed that the gillnet types with different hanging ratios at the top and down ropes, recorded superior efficiencies over the gillnet types with same hanging ratios. It was concluded that different hanging ratios, at the top and down ropes, combined with slack netting constituted a superior intervention for enhancing technical and economic efficiencies of monofilament gillnets.

Length‐weight relationship for two flounder species from Iranian waters of the Persian Gulf

The length-weight (LWR) relationship was estimated for the first time for two flounder species viz. Pseudorhombus elevatus Ogilby, 1912 and Solea elongata Day, 1877 from Iranian waters of the Persian Gulf. Fishes were collected using fishing boat during August to December 2017. No information is available in FishBase regarding the LWRs of these species. The b values of the LWR was 2.98 for P. elevatus and 3.10 for C. elongate , and the r 2 values are 0.996 and 0.989, respectively. These estimates can be used for estimation of biomass of the studied fishes employing length frequency distributions.

Assessing sources of uncertainty in length-based estimates of body growth in populations of fishes and macroinvertebrates with bootstrapped ELEFAN

The determination of rates of body growth is the first step in many aquatic population studies and fisheries stock assessments. ELEFAN (Electronic LEngth Frequency ANalysis) is a widely used method to fit a growth curve to length-frequency distribution (LFD) data. However, up to now, it was not possible to assess its accuracy or the uncertainty inherent of this method, or to obtain confidence intervals for growth parameters within an unconstrained search space. In this study, experiments were conducted to assess the precision and accuracy of bootstrapped and single-fit ELEFAN-based curve fitting methods, using synthetic LFDs with known input parameters and a real data set of Abra alba shell lengths. The comparison of several types of bootstrap experiments and their outputs (95% confidence intervals and confidence contour plots) provided a first glimpse into the accuracy of modern ELEFAN-based fit methods. The main components of uncertainty (precision and reproducibility of fit algorithms, seed effects, sample size and matrix information content) could be assessed from partial bootstraps. Uncertainty was mainly determined by LFD matrix size (months x size bins), total number of non-zero bins and the sampling of large-sized individuals. A new pseudo-R² index for the goodness-of-fit of von Bertalanffy growth models to LFD data is proposed. For a large, perfect synthetic data set, pseudo-R²Phi’ was very high (88 to 100%), indicating an excellent fit of the growth model. The small Abra alba data set showed a low pseudo-R²Phi’, from to 54% to 68%, indicating the need for more samples (length measurements) and a larger LFD data matrix. New, robust, bootstrap-based methods for curve fitting are presented and discussed. This study demonstrates a promising new path for length-based analyses of growth and mortality in natural populations, which are the basis for a suite of methods that are included in the new fishboot package.

Estructura poblacional y biología reproductiva del tiburón martillo Sphyrna lewini (Carcharhiniformes: Sphyrnidae) capturado en la pesca artesanal de Oaxaca, México

Background: Sphyrna lewini, is a semi-oceanic and cosmopolitan species globally distributed throughout tropical and warm temperate seas. In the northeastern tropical Pacific, this specie represents an important contribution to the biomass of artisanal and small-scale fisheries. Goals: In this study the aim was to obtain information about length frequency distribution and reproductive aspects of S. lewini, in Oaxaca, Mexico. Methods: Samples were taken from August 2001 to December 2007 in four landing sites of the artisanal fleet on the coast of Oaxaca. Results: Samples were collected 388 females and 434 males. Total length ranged from 44-308 cm for males and from 44-332 cm for females. The catches were made up of neonates (24.3%, 44-74 cm), juveniles (42.2%, 75-170 cm) and adults (33.5%, > 170 cm). The sex ratio shows differences by size, and season. The greatest catches were recorded in the rainy season (85.5%), with a predominance of juveniles and adults, and a higher proportion of males. In the dry season (15.5%) were recorded with a predominance of larger sizes >100 cm in both sexes. The females reached sexual maturity (TL50) at 198.8 cm and the males at 181 cm, based on characteristics and measurements of reproductive organs. A total of 37 gravid females with sizes between 175 and 281 cm were registered, from April to August. Gravid females had between 15-42 embryos, varying from 44-54 cm. Conclusion: S. lewini was present year round in the study area with the greatest catch from April to September, the season when pregnant females were present.

Temporal variation of sex ratio, growth pattern and physiological status ofEutropiichthys vacha(Schilbeidae) in the Ganges River, NW Bangladesh

ABSTRACTThe present study illustrates the first complete temporal variations of sex ratio (SR), length-frequency distributions (LFDs), growth pattern based on length-weight relation (LWR), length-length relationships (LLRs) and physiological status of Eutropiichthys vacha in the Ganges River, Bangladesh. A total of 1386 specimens (male = 652, female = 734) were collected from the fishers catch during January to December, 2016. For each individual, total length (TL), fork length (FL), standard length (SL) and body weight (BW) were measured using digital slide calipers and electronic balance with 0.01 cm and 0.01 g precision. The overall SR differed statistically from the expected 1:1 ratio, although females were greater in percentage throughout the year, except in April. The TL of males and females ranged from 6.2–19.9 cm and 6.5–20.6 cm, respectively. The overall growth pattern was negative allometric for both sexes, though ANCOVA reveals significant difference in LWRs. All LLRs were highly significant wi...

Reproductive strategy of spadenose shark, Scoliodon laticaudus Muller and Henle, 1839 along north-eastern Arabian Sea

Scoliodon laticaudus constitute a major fishery along the north-west maritime states of India. Despite its contribution to the fishery, there is a dearth of information about the reproductive characteristics of the species in the region. The limited fecundity and its distribution in sensitive ecosystem could make it vulnerable to the impacts of targeted fishing and habitat degradation. Therefore, the present study was envisaged to collect information about the reproductive strategy of the shark which is essential for developing proper management measures for the sustainable exploitation of the resource. A total of 1,277 S. laticaudus specimens were studied to collect information about the maturity parameters, reproductive periodicity and reproductive potential of the species from the Gujarat coast of India. The length frequency distributions for both the sexes showed that mean and modal lengths of the exploited shark were 40.5 cm and 47.5 cm, respectively. Male and female sharks were found to mature at lengths of 33.8 cm and 35.8 cm, respectively which were lower compared to the predominantly targeted length group of the fishery. Though large and ripe ova were observed along with small developing ova throughout the year in the ovaries of the shark, significant increase (p ≤ 0.01) in mean ova diameter was observed during March and April followed by October and November which suggest the peak reproductive period of the shark. There was a significant relationship (p ≤ 0.01) between maternal body size and litter size where the larger females were recorded to produce more number of embryos compared to the smaller ones. The actual number of embryos carried by a single female ranged from a minimum 8 to a maximum of 19 embryos per pregnant female, with a mean embryo number of 10 per pregnant female. The higher mean size of embryos was recorded in August and September which coincided with the highest number of post-partum females and therefore, might be considered as the major parturition period. The length at birth (L0) was calculated to be 13.7 cm. The breeding behavior of the species appeared to be continuous as developed embryos were observed throughout the year. The present study provides vital information for deriving the appropriate size and time for the sustainable exploitation of the resource. Further study should be conducted to understand the relationship between spawning stock biomass and recruitment dynamics considering the lower reproductive potential of the species so that the optimum spawning biomass could be assessed to ensure sustainability of this resource.

A holistic approach to the age validation of Mullus barbatus L., 1758 in the Southern Adriatic Sea (Central Mediterranean)

The growth of Mullus barbatus has been widely studied using different methods, but no previous study has focused on age validation. The uncertainty in estimating the age of the red mullet by otolith reading is linked to the number of false-growth increments laid down before the annulus. The capture of red mullets in the early life stage allowed us to estimate their size at the metamorphosis from the pelagic to the demersal phase. The comparison between the metamorphosis size and the back-calculated length of the first growth increment clarified the position of the false growth increment on the otolith. Moreover, the analyses of the otolith marginal increments in adult and juvenile specimens allowed us to define the deposition patterns of their annuli. The modal components of the length–frequency distribution analysis (LFDA) were identified in the winter survey (ELEFAN and Bhattacharya methods), and they did not show significant differences from the length back-calculation of the annuli. Moreover, no significant differences were found between the growth curves calculated by otolith reading (back-calculation and direct otolith reading) and the LFDA. The agreement between the length–frequency results and the otolith age estimation either corroborated or indirectly validated the growth pattern estimated in the otoliths of the red mullet, mainly when the direct validation methods (e.g. mark-recapture, captivity, radiochemical) were difficult to implement, like the case of this species. The comparison of the results of the present work to previous Mediterranean studies showed agreement with the slow growth pattern.

Mode technology assessment of mass transport master plan in Greater Jakarta (Jabodetabek)

The aim of this paper is to evaluate the appropriateness of the proposed mass transit mode technology in the Greater Jakarta (Jabodetabek) Public Transport Master Plan. The analysis is focused on the estimated demand on the proposed bus rapid transit (BRT) network. A transport demand model based on the four step modeling approaches is prepared to estimate the demand on each proposed BRT route. Prior conducting a simulation, the model developed from previous works is calibrated and validated with various primary data namely, trip length frequency distribution and bus passenger data obtained from the field. In parallel, some assumptions and operational scenarios were established by taking into account the total number of ridership, maximum passenger flow, operational headway and proposed mode capacity. The appropriateness of the proposed mode was assessed and analyzed. The results show that the ridership and operational headway exceed the standard commonly used for the operational aspects of BRT on some proposed BRT routes. In addition, the evaluation shows that the proposed routes should be shifted to a rail base mass transit technology in order to maintain best level of services.

Behavioral pattern of pill bugs revealed in virtually infinite multiple T-maze

A behavior called turn alternation has been studied extensively in terrestrial isopods. This behavior is seen when they alternate their path choice on successive trials of the T-maze test. We made the multiple T-maze device which consists of two turntables with a T-maze mounted on each and examined the behavior of 36 pill bugs (Armadillidium vulgare) that each completed 130 successive T-maze trials. As a result, in addition to turn alternation, turn repetition (turning in the same direction on two successive turns) appeared at a rate of 20%. In the turn sequences, we observed segments consisting of successive turn alternations and defined the number of turn alternations in a segment as the length of it. Cumulative frequency distribution of segment lengths obeyed power law with exponent of 1.76. This result suggests that pill bugs in the multiple T-maze device behaved as Levy walkers which forage in an environment, where resources are unpredictably distributed.

Spatial and temporal dynamics of European hake (Merluccius merluccius) in the North Sea

Abstract Catches of European hake (Merluccius merluccius) in the North Sea have increased substantially during the last decade, even though there is no directed commercial fishery of hake in this area. We analysed the spatial distributions of hake in the northern the parts of its range, (where it is less well-studied), using ICES international bottom trawl survey data from 1997 to 2015. We examine length-frequency distributions for (i) distinct modes enabling the assignment of fish into categories which likely corresponded to the ages 1, 2, and 3+ and (ii) patterns of seasonal spatial distribution for the different groups. Age categories 1 and 2 fish were most abundant in the northern North Sea, and appear to remain in the North Sea until 2 years of age, when they move into deeper waters. Their distribution has expanded into the western-central North Sea in the last decade. Age category 3+ fish were most abundant in the northern and central North Sea during summer, indicating a seasonal influx of large individuals into this area likely associated with spawning activity. The distribution of these older fish has gradually expanded westward in both seasons.

Growth of the Anchovy Anchoa tricolor in a brazilian subtropical estuary.

This study aimed to describe the growth parameters of Anchoa tricolor in a subtropical estuary. From August 2010 to July 2011, 10.009 specimens of the anchovy Anchoa tricolor, mean total length 4.2 cm (±1.45), were captured in the intertidal region of the Estuarine Complex of Paranaguá (25º 15' - 25° 35' S and 48° 20' - 48° 45' W). Species´s weight/length relationship for grouped genders was described as follow: W = 0.0000591.Lt3.282 (length in centimeters; weight in grams) showing a positive allometric growth pattern (b>3; P=0.000). Significant differences concerning weight/length relationship for males, females and unsexed individuals were identified. Parameters of the length to age growth curve were estimated by adjusting a von Bertalanffy growth equation from aged individuals from a length-frequency distribution: L∞ = 10.06 (1-e-17715(t + 0.205)) (length in centimeters, age in years). The age to attain 95% of the asymptotic length ( A95 ; longevity sensu Taylor) was estimated at 1.7 years. Size frequency distributions indicate that A. tricolor uses the estuarine area as reproductive and growing grounds, especially during the first year of the life cycle, where the species represent a key element for ecosystem functioning due to relatively high abundance and energy transference from plankton to top predators.

Impacts of hatchery-reared mandarin fish Siniperca chuatsi stocking on wild fish community and water quality in a shallow Yangtze lake

Mandarin fish Siniperca chuatsi, a valuable piscivorous fish, have been stocked into many lakes in China since the 1990s. This study did the first attempt to evaluate the ecological effects of hatchery-reared mandarin fish stocking in the Yangtze River basin lakes. Our study demonstrated a significant change in fish community composition after mandarin fish stocking, but no fish extinction was observed. No significant difference was observed in the total density of 13 forage fish before and after mandarin fish stocking, but the total biomass showed a significant decline after mandarin fish stocking. Significant differences in length-frequency distributions were observed for Carassius auratus, Pseudorasbora parva and Toxabramis swinhonis captured before and after stocking mandarin fish. No significant change in habitat distribution was detected before and after mandarin fish stocking. A marked decline in total nitrogen and a slight decline in total phosphorus were observed while a slight increasing trend for Secchi depth was found after stocking. Our findings suggested that mandarin fish stocking can increase predation pressure on forage fish and subsequently optimize the food web structure. Also, mandarin fish stocking has the potential to improve water quality and may be a feasible strategy to alleviate eutrophication of shallow Yangtze lakes.

Seasonal changes in fish catch and environmental variables in a large Tropical Lake, Volta, Ghana

AbstractFish species assemblage and selected environmental variables were monitored in Lake Volta from September 2014 to August 2016 to determine seasonal variability in species composition, catch and environmental variables that determine the structure of the fish community. A total of 1,557 individual fish belonging to 41 species, 25 genera and 13 families were recorded. The important fish species with respect to frequency of occurrence, abundance and weight, respectively, were as follows: Chrysichthys (100%; 43.03%; 17.93%), tilapias (100%; 28.97%; 17.86%), Alestes (100%; 14.13%; 32.10%) and Bagrus (91.67%; 5.65%; 12.80%) in that order. The composition of fish species and their temporal variation in experimental catches were similar to that of commercial catches. There were no significant differences (p &gt; 0.05) in species abundance, weight and diversity indices between the dry and wet seasons. The modal class of length frequency distribution of the dominant species in the catch, Chrysichthys, reduced from 125 mm in 2006 to 95 mm in the current study indicating overfishing. Environmental variables considered showed little variation and within optimal ranges for fish survival and did not differ significantly between seasons. Canonical Correspondence Analysis showed that environmental variables explained 43.30% of the variation in species abundance with Lake water level, nitrite‐nitrogen and total dissolved solids being the main environmental factors influencing the structure of the fish community.

Population dynamics of Prochilodus nigricans (Characiformes: Prochilodontidae) in the Putumayo River

ABSTRACT The black prochilodus (Prochilodus nigricans) is one of the most landed scaled fish species of the middle and upper parts of the Putumayo River, in the tri-national area between Colombia, Ecuador and Peru. Despite its importance, biological information about this species is too scant to guide fisheries management in this portion of the Colombian Amazon. In this study, 10884 individuals were sampled in the fish markets of Puerto Leguízamo between 2009 and 2017. This sampling was used to document reproductive patterns, but also growth and mortality parameters from length frequency distributions. The size at which all fish were mature was 22 cm Ls, which should be the established as the minimum size of capture to ensure that all fish have had a chance to reproduce before being caught. Growth and mortality parameters indicated a slower growth in the Putumayo than in other Amazonian rivers and a relatively high exploitation rate.

Sexual dimorphism in the gammaridean amphipod, Urothoe carda Imbach, 1967, from an intertidal sandflat in southern Japan

AbstractSpecies of the gammaridean amphipod genus, Urothoe, commonly occur on intertidal and shallow subtidal sandy bottoms. Sexual dimorphism is reported for some species of Urothoe, but the descriptions are semi‐quantitative, lacking allometric growth models. A distinct sexual dimorphism was detected in Urothoe carda Imbach, 1967 collected from an intertidal sandflat in western Kyushu, Japan, in March, June, August, and October, 2015. The analysis for the total length–frequency distribution and maturity in each sex showed a female‐biased sex ratio (3.6 for mature individuals). Mature males had the larger eye and longer antenna 2 versus total length, expressed as generalized linear models (gamma distribution; logarithmic link‐function). Based on other studies on Urothoe spp. and peracarids, the above differences may suggest higher mate searching activity in male U. carda, with its larger eye functioning during the nocturnal excursion into the water column and its longer antenna 2 equipped with calceoli effective in detecting receptive females in the sediment.