Differences In Length Frequency Distributions Research Articles

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.

Evaluation of Potential Overwinter Mortality of Age-0 Walleye and Appropriate Age-1 Sampling Gear

AbstractPotential recruitment of age-0 Walleye Sander vitreus to adults is often indexed by the relative abundance of age-0 individuals during their first summer or fall. However, relationships between age-0 and adult Walleye abundance are often weak or nonsignificant in many waters. Overwinter mortality during the first year of life has been hypothesized as an important limitation to Walleye recruitment in lakes, but limited evidence of such mortality exists, likely due to difficulties in sampling age-1 Walleye during spring. The objectives of this study were to: 1) compare results from nighttime electrofishing to index relative abundance of age-1 Walleyes with relative abundance indices of minifyke nets in four eastern South Dakota lakes; 2) determine whether size-selective mortality was occurring in those four lakes; and 3) if size-selective mortality was occurring in these lakes, determine whether that mortality was attributed to body condition. We sampled four natural lakes in eastern South Dakota 2 wk after ice-off in 2013 and 2014. Precision of nighttime electrofishing (coefficient of variation = 216.6) was greater than that estimated for minifyke nets (coefficient of variation = 338.5) across both years. We detected no differences in length-frequency distributions of collected spring age-1 Walleye between the two gears. Age-0 fall relative abundance indices from electrofishing were significantly greater (P < 0.01) than spring age-1 nighttime electrofishing indices of relative abundance at three of the four study lakes, indicating that overwinter mortality may occur at a substantial rate during the first year of life for Walleye in these systems. Quantile–quantile regression plots showed evidence of size-selective mortality in three of four lakes sampled. However, body condition of age-0 Walleye appeared to have little to no influence on overwinter mortality. Instead, we suggest that smaller-sized walleye may be more vulnerable to overwinter predation. Collectively, these results provide evidence of previously hypothesized overwinter mortality within the first year for Walleye and indicate possibilities for indexing potential adult recruitment of Walleye just after this critical period.

Reproductive biology of Psammobatis rutrum (Chondrichthyes: Arhynchobatidae) in south Brazil, south-west Atlantic.

This study presents information on the reproductive biology of Psammobatis rutrum based on 55 males and 53 females obtained as by-catch from bottom trawlers off southern Brazil during July 2013 and September 2014 and includes a detailed description of the egg capsule. Total lengths (LT ) ranged from 22·3 to 31·6 cm and most of the sample comprised larger individuals, although there were no sexual differences in length-frequency distributions. Significant sexual differences were found for total length-disc width, LT -body mass and LT -eviscerated body mass relationships, with females being heavier and larger. Males started to mature at 25·5 cm LT and females, at 25·9 cm LT , while LT at maturity was calculated in 26·67 and 26·81 cm, respectively. Attaining larger sizes and mass may represent a reproductive investment for females, as observed in other rajoid species. Egg bearing females were first observed over 27·1 cm LT and ovarian fecundity was 1-12 vitellogenic follicles. The egg capsules were 2·22-2·62 cm length and had attaching fibrils on both lateral sides. Microscopically, the ventral face of the egg capsule was rougher than the dorsal face.

Distribution of demersal fishes along the US west coast (Canada to Mexico) in relation to spatial fishing closures (2003-2011)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 501:169-190 (2014) - DOI: https://doi.org/10.3354/meps10674 Distribution of demersal fishes along the US west coast (Canada to Mexico) in relation to spatial fishing closures (2003-2011) Aimee A. Keller1,*, W. Waldo Wakefield2, Curt E. Whitmire2, Beth H. Horness1, Marlene A. Bellman1, Keith L. Bosley2 1Fishery Resource Analysis and Monitoring Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Boulevard East, Seattle, Washington 98112, USA 2Fishery Resource Analysis and Monitoring Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanographic and Atmospheric Administration, 2032 S. OSU Drive, Newport, Oregon 97365, USA *Corresponding author: aimee.keller@noaa.gov ABSTRACT: A temporally and spatially variable Rockfish Conservation Area (RCA) was established as a marine protected area along the US west coast in 2002 to protect stocks of rockfishes Sebastes spp. Since the RCA falls within the region sampled annually by the West Coast Groundfish Bottom Trawl Survey, we utilized data collected from 2003 to 2011 to evaluate whether establishment of the RCA influenced catch per unit effort (CPUE), species richness, and size distribution of demersal fishes. We compared CPUE and species richness among 3 management areas (continuously closed, periodically closed, and open to commercial bottom trawling) using analysis of covariance models that account for variability due to area, year, and depth. The most appropriate models for CPUE (35 species treated individually and aggregated into 6 subgroups) and species richness were selected using Akaike’s information criterion. All of the best-fit models were highly significant (p < 0.0001), explaining 3 to 76% of the variation in catch. For 27 species and 5 subgroups, mean CPUE was significantly greater within the area continuously closed to commercial bottom trawling relative to areas periodically closed or open. The most appropriate model for richness included area and year, and mean richness was greatest in the area continuously closed to trawling. Species-specific length composition distributions were calculated from subsampled individual lengths for 31 species. Significant differences in length frequency distributions were observed, with a higher proportion (~65%) of larger fish most often present in areas continuously closed to commercial bottom trawling (20 of 31 species) relative to other areas. Our data suggest that the RCA is an effective management tool for conserving not only rockfishes, but also other demersal fish species. KEY WORDS: California Current System · Demersal fishes · Spatial fisheries management · Rockfish Conservation Area Full text in pdf format PreviousNextCite this article as: Keller AA, Wakefield WW, Whitmire CE, Horness BH, Bellman MA, Bosley KL (2014) Distribution of demersal fishes along the US west coast (Canada to Mexico) in relation to spatial fishing closures (2003-2011). Mar Ecol Prog Ser 501:169-190. https://doi.org/10.3354/meps10674 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 501. Online publication date: March 31, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

제3기 결정질 응회암에서 발달하는 미세균열의 길이 분포에 대한 통계적 분석

제3기 결정질 응회암에서 발달하는 미세균열 모집단의 길이분포에 대한 스케일링 성질을 조사하였다. 15개 방향각 및 5개 그룹 (I~V)에 대한 길이범위의 분포도에서 미세균열의 방향성에 따른 평균길이의 체계적인 변화가 나타난다. 분포도는 거의 남-북방향을 경계로 하여 좌우 대칭형태를 취하는 것이 특징이다. 미세균열의 모집단에 대한 길이-누적빈도 도표의 전 영역은 상관곡선의 분포양상에 의하여 3개 구간으로 구분할 수 있다. 특히, 5개 그룹에 대한 각 도표의 선형의 중앙구간은 멱함수 분포를 지시한다. 5개 그룹에 대한 중앙의 선형구간의 빈도비는 46.6%~67.8T의 범위이다. 한편 각 그룹에 대한 선형의 중앙구간의 기울기는 그룹 V(<TEX>$N60{\sim}90^{\circ}E$</TEX>, -2.02) > 그룹 IV(<TEX>$N20{\sim}60^{\circ}E$</TEX>, -1.55) > 그룹 I(<TEX>$N60{\sim}90^{\circ}W$</TEX>, -1.48), 그룹 II(<TEX>$N10{\sim}60^{\circ}W$</TEX>, -1.48) > 그룹 III(<TEX>$N10^{\circ}W{\sim}N20^{\circ}E$</TEX>, -1.06)의 순으로 나타난다. 거의 멱함수의 길이분포를 따르는 부집단(5개 그룹)에서는 지수(-1.06~-2.02)의 범위가 넓다. 5개 그룹간의 이러한 지수의 상대적인 차이는 방향성 효과의 중요성을 강조한다. 또한, 곡선의 하부에서의 기울기의 분리는 보다 긴 미세균열의 급격한 발달을 대변하며, 멱함수 지수의 감소로 반영된다. 특히, 이러한 분포양식은 <TEX>$N10{\sim}20^{\circ}E,\;N10{\sim}20^{\circ}W$</TEX> 및 <TEX>$N60{\sim}70^{\circ}W$</TEX>의 방향각에 대한 도표에서 볼 수 있다. 이들 3개 방향각은 연구지역 일대에서 발달한 단층의 주방향과 부합한다. 15개 방향각에 대한 길이-누적빈도 도표의 개개 특성을 보여주는 분포도를 작성하였다 상기한 도표들을 3개 그룹(A, B and C)의 범주에 따라 배열함으로서 이들 그룹간 길이-빈도 분포의 차이를 용이하게 도출할 수 있다. 분포도는 미세균열 조들에 대한 개별적인 분리의 중요성을 보여준다. 관계도에서, 보다 짧은 미세균열의 출현빈도는 그룹A > 그룹 B > 그룹 C의 순서를 보인다. 이들 3가지 유형의 분포양상은 미세균열이 성장하는 동안 발생한 과정들에 대한 중요한 정보를 드러낼 수 있다. The scaling properties on the length distribution of microcrack populations from Tertiary crystalline tuff are investigated. From the distribution charts showing length range with 15 directional angles and five groups(I~V), a systematic variation appears in the mean length with microcrack orientation. The distribution charts are distinguished by the bilaterally symmetrical pattern to nearly N-S direction. The whole domain of the length-cumulative frequency diagram for microcrack populations can be divided into three sections in terms of phases of the distribution of related curves. Especially, the linear middle section of each diagram of five groups represents a power-law distribution. The frequency ratio of linear middle sections of five groups ranges from 46.6% to 67.8%. Meanwhile, the slope of linear middle section of each group shows the order: group V(<TEX>$N60{\sim}90^{\circ}E$</TEX>, -2.02) > group IV(<TEX>$N20{\sim}60^{\circ}E$</TEX>, -1.55) > group I(<TEX>$N60{\sim}90^{\circ}W$</TEX>, -1.48), group II(<TEX>$N10{\sim}60^{\circ}W$</TEX>, -1.48) > group III(<TEX>$N10^{\circ}W{\sim}N20^{\circ}E$</TEX>, -1.06). Five sub-populations(five groups) that closely follow the power-law length distribution show a wide range in exponents( -1.06 - -2.02). These differences in exponent among live groups emphasizes the importance of orientation effect. In addition, breaks in slope in the lower parts of the related curves represent the abrupt development of longer lengths, which is reflected in the decrease in the power-law exponent. Especially, such a distribution pattern can be seen from the diagram with <TEX>$N10{\sim}20^{\circ}E,\;N10{\sim}20^{\circ}W$</TEX> and <TEX>$N60{\sim}70^{\circ}W$</TEX> directional angles. These three directional angles correspond with main directions of faults developed around the study area. The distribution chart showing the individual characteristics of the length-cumulative frequency diagrams for 15 directional angles were made. By arraying above diagrams according to the categories of three groups(A, B and C), the differences in length-frequency distributions among these groups can be easily derived. The distribution chart illustrates the importance of analysing microcrack sets separately. From the related chart, the occurrence frequency of shorter microcracks shows the order: group A > group B > group C. These three types of distribution patterns could reveal important information on the processes occurred during microcrack growth.

Age and growth of sea perch ( Helicolenus percoides) from two adjacent areas off the east coast of South Island, New Zealand

A validated ageing methodology using otolith thin sections is presented for sea perch ( Helicolenus percoides) in two adjacent areas off the east coast of South Island, New Zealand. Oxytetracycline marking of two adult fish held in captivity for 1 year suggested that a single dark growth increment formed during winter, commencing May or June. The annual formation of growth increments was confirmed by the observed progression of year classes in comparable samples from three different years, and the progression of length modes in several consecutive years that matched the estimated growth curves. Otolith interpretation was difficult because of a central dense region and the presence of many fine bands within each growth increment, but the latter could be counted, and it is considered that a validated ageing procedure is presented. Von Bertalanffy growth parameters were calculated for east coast South Island (ECSI) and Chatham Rise males and females. In both areas the growth rate of males is slightly but significantly faster than for females. Growth is relatively slow throughout life. From the maximum observed ages for ECSI and Chatham Rise fish of 35 and 59 years, the respective natural mortality rates are estimated to be 0.12 and 0.07 year −1, but the most plausible value for the species is likely to be at the lower end of this range. Some stock differentiation between the two areas is indicated, based primarily on differences in length-frequency distributions implying different patterns of year class strengths, but also on apparent differences in growth rates between areas. This supports the present management regime of separate commercial catch quotas.

Effects of mangrove deforestation on fish assemblage at Pak Phanang Bay, southern Thailand

Daytime sampling using a seine net was conducted at Pak Phanang Bay (Nakhon Si Thammarat Province, Thailand) in February and July 2006, to determine differences in fish assemblage structures between a mangrove site and an adjacent site completely cleared of mangroves. The overall numbers of fish species and individuals were significantly higher at the mangrove site than the cleared site in both months. Although benthic crustacean feeders showed more species and individual numbers at the mangrove site in both months, the opposite was found for zooplankton feeders. A cluster analysis, based on the abundance of each species, demonstrated that the fish assemblage structures were distinctly different between the two sites. In addition, significant differences in length frequency distributions for each of the four most abundant species were found between the sites in February and/or July. Small individuals of Scatophagus argus, Ambassis nalua, and Tetraodon nigroviridis were more common at the mangrove site, and of Chelon subviridis at the cleared site. These results suggest that mangrove deforestation exerts marked effects on fish assemblages.

Variability in low tide populations of tuatua, Paphies donacina, in Pegasus Bay, Canterbury, New Zealand

Paphies donacina (Spengler, 1793) populations were surveyed at 11 low tide sites on surf beaches along Pegasus Bay, Canterbury, New Zealand, during summer 1998. Random sampling was not feasible. At the non‐random sites chosen the average number of tuatua per 5 m of shoreline ranged between 0.1 and 62. Total wet weight biomass m‐2 was highest at the southern sites in the Bay. There were site‐related differences in length frequency distributions of tuatua populations. Northern populations included a wide length range and southern populations were dominated by larger bivalves. Average shell length increased significantly with distance south, being close to 40 mm at Waikuku and 80 mm at Taylors Mistake. The shell length: width and weight relationships were similar for tuatua collected over the whole geographic range. Average dry weight condition index varied significantly between sites (ANOVA F= 23.3, d.f. = 10, 329) depending on the length distribution of the contributing population. Where populations included a wide length range the condition index was positively correlated with shell length but in populations dominated by larger bivalves there was either no relationship or a negative relationship with shell length. Juvenile tuatua were found at average densities between 81 and 1200 m‐2 at all sites except Taylors Mistake. The mean length of recruits ranged from 2.2 to 3.1 mm and shell length was independent of both juvenile and adult density. These results are discussed in relation to the environmental and other factors thought to influence population structure and recruitment of tuatua in Pegasus Bay.

Abundance, Length Composition, and Migration of Spawning Inconnu in the Selawik River, Alaska

Abstract Inconnus Stenodus leucichthys in the Selawik River, Alaska, were sampled during spawning migrations in the years 1993–1996. Modified Petersen estimates of spawning inconnu were 5,190 (95% confidence interval = 3,690–7,272) for 1995 and 5,157 (3,038–12,983) for 1996. Fork lengths of migrating fish ranged from 52 to 120 cm. Minor differences in length-frequency distributions were observed among the 3 years sampled. Migrating inconnu reached holding areas 25 km below the spawning area in the first week of July and resided there for up to 1 month. Further upstream movement in late August was associated with precipitation. A short reach of river, approximately 12 km long, was identified as the spawning area by use of radiotelemetry. Postspawning migrations occurred as early as September 27 and were completed by October 19. Dispersal during the winter, as measured by tag returns, showed mixing with Kobuk River inconnu within the Selawik Lake–Hotham Inlet complex. Lack of observed interdrainage migratio...

Hand Grappling Blue Catfish in the Main Channel of a Mississippi River

Blue catfish Ictalurus furcatus were hand grappled, primarily by using scuba gear, from 30.5-cm-square × 122-cm-long wood boxes, May through July 1990–1993 in the Tallahatchie River, a principal tributary of the Yazoo River in Mississippi. During January through August 1990–1994, blue catfish also were collected with hoop nets (4.3 m long, having seven hoops with 1.07 m diameters and 3.81-cm-bar-mesh netting), which are standard gear for riverine fish stock assessments in Mississippi. During the study, 638 grabs yielded 29 blue catfish, and 638 overnight hoop-net sets yielded 71 blue catfish. Hand grappling caught larger blue catfish than did hoop netting. Mean total lengths (TL) of blue catfish captured by hand grappling and hoop netting were 77.3 em (SE, 2.1 cm) and 48.3 cm (SE, 0.8 cm), respectively. There were also differences in length-frequency distributions between methods, which confirmed hand-grappling selectivity for larger blue catfish. Overall. the hand-grappling catch rate for the entire study was about 24–25 grabs per fish captured. The overall hoop-netting catch rate was about 9–10 net sets per fish captured and about 50 net sets per fish captured for fish 60 cm TL or longer, which was the minimum size captured by hand grappling. Siltation in conjunction with strong currents and fluctuations in water level created logistic challenges to hand grappling. Hand grappling, as a specialized fishery, should be viewed as another component in the suite of environmental and sociological concerns linked to conservation initiatives for floodplain river ecosystems in the United States.

Estimating length frequency distributions of large reef fish underwater

We describe the training of divers to recognise and remove bias in estimating lengths of fish underwater. Divers were asked to allocate objects, from a population (N=50) with a known length frequency distribution, to ten 100 mm size classes. Observed and expected distributions were then compared and the divers informed of their errors. Training continued until divers consistently produced length frequency distributions that were not significantly different from the expected distribution (α=0.8) by the one sample Kolmogorov-Smirnov (K-S) test. Divers were trained in five trials, but after six months they had lost all their ability and had to be retrained. Three trained divers observing the “same” population of the large reef fish Plectropomus leopardus (Serranidae) produced length frequency distributions that were not significantly different (P>0.1) on 67% of occasions. Data collected by divers can be used to detect small but real differences in length frequency distributions of populations when analysed using the two sample K-S test. We suggest a means of determining within site variation in length frequency relative to between site variation.

Stock Structure of Rainbow Smelt in Western Lake Superior:Population Characteristics

Abstract Significant differences in length-frequency distributions, fecundity, and growth of rainbow smelt Osmerus mordax were found among collections from three zones along the Minnesota shoreline of Lake Superior. These differences were consistent with genetic evidence suggesting three discrete stocks of rainbow smelt. Geographic separation, possibly in combination with predation, may have been responsible for the isolation of stocks to the extent that local adaptations resulted in the observed differences. Although statistically significant, the actual differences in traditional population characters appeared small, potentially a result of weak or recently applied selective pressures. Future changes in predatory or competitive pressures or changes in exploitation rates may alter selective pressures and thus may have important influences on dynamics and condition of rainbow smelt stocks in Lake Superior. Received August 30, 1983 Accepted August 24, 1984