Analysis Of Length-frequency Data Research Articles

Change in body size in a rapidly warming marine ecosystem: Consequences of tropicalization

Climate change is profoundly affecting the physical environment and biota of the Northeast U.S. Continental Shelf ecosystem. To understand adaptations to climate change, in particular warming temperatures, we used bottom trawl survey data to describe the size of individual fish and macroinvertebrates. Using species distribution models to estimate abundance and biomass, we determined body size in weight for all modeled species. We demonstrate a tendency for increased abundance and biomass and a concomitant decline in body size over time. An analysis of length frequency data supports this assertion. There was no trend in the combined anthropogenic removals from the ecosystem, i.e. catches, suggesting a limited role of fisheries in influencing these changes. The changes in the fish and macroinvertebrate communities are consistent with the hypothesis of a tropicalization of this ecosystem, where the ecosystem experiences a change in diversity, abundance, biomass, and the size of individuals consistent with lower latitudes. The changes in how productivity is expressed in the ecosystem factors into how human populations relate to it; in a practical sense, change in body size will likely influence the strategies and efficiencies of harvest procedures and the industries built to support them.

Estimation of Growth Parameter on Sailfin Catfish (Pterygoplichthys pardalis) in Bengawan Solo River, Central Java Province

Bengawan Solo river 548.53 km is the longest river in Java Island Indonesia, which crosses provinces of Central Java and East Java. Bengawan Solo river is heavily polluted by agricultural, industrial and domestic wastes, especially in Surakarta Residence, Central Java. The impacts of pollution in Bengawan Solo river are poor water quality, the population of native fish has declined sharply and some were almost extinct. The fish that develop was Sailfin catfish (Pterygoplichthys pardalis) because these fish were resistant to pollution. The study aimed to determine the growth parameters of Sailfin catfish (P. pardalis) in Bengawan Solo river. Estimation of growth parameter using length frequency data analysis was done using the FISAT program package. The results of growth parameters of Sailfin catfish (P. pardalis) showed that infinity length (L∞) = 41.75 cm; acceleration of growth (K) = 0.48 cm/year. Natural mortality (M) = 1,1; fishing mortality (F) = 2.47; and total mortality (Z) = 3.57. Exploitation rate (E) = 0.69. The conclusion is the fishing mortality of Sailfin catfish is quite high, while natural mortality is low because the fish are resistant to pollution.

Bycatch of the Isla del Rosario (Gulf of Salamanca, Colombian Caribbean) artisanal shrimp fishery in an approximation to the biodiversity impact

In the period March 2009-February 2010 the fish bycatch of the artisanal shrimp fishery operating off the beach of Isla del Rosario (Gulf of Salamanca, Colombian Caribbean) was evaluated and length-frequency data analysis were done for five of the main ichthyic species. For this purpose, data registered in the project “Pesca artesanal del Magdalena”, processed in the Fisheries Information System of Invemar (SIPEIN) to obtain fishery variables, on a monthly basis, was used. Between shrimp and fish fauna 38,265 kg were registered. The ichthyic bycatch fauna was composed of 59 fish species, distributed in 23 families, being Engraulidae, Sciaenidae, and Mugilidae the most representative. Regarding the engraulid Cetengraulis edentulus biomass, it was the most important species. Ichthyic bycatch to shrimp relationship was 1.2:1.0 with shrimp beach seine. During the assessed year, the highest mean Landing Per Unit Effort (LPUE) was present in the dry season, but November (rainy season) was the month with the highest shrimp LPUE. The indicators, Lc (mean length) and spawning/juvenile proportion, evidence growth overfishing for the species Bairdiella ronchus , Cathorops mapale , Mugil incilis and Trichiurus lepturus . The state of this fishery and the impact it generates on the ecosystem is discussed. Measures for its proper management are recommended.

A new approach for estimating stock status from length frequency data

Abstract This study presents a new method (LBB) for the analysis of length frequency data from commercial catches. LBB works for species that grow throughout their lives, such as most commercially-important fish and invertebrates, and requires no input in addition to length frequency data. It estimates asymptotic length, length at first capture, relative natural mortality, and relative fishing mortality. Standard fisheries equations can then be used to approximate current exploited biomass relative to unexploited biomass. In addition, these parameters allow the estimation of length at first capture that would maximize catch and biomass for a given fishing effort, and estimation of a proxy for the relative biomass capable of producing maximum sustainable yields. Relative biomass estimates of LBB were not significantly different from the “true” values in simulated data and were similar to independent estimates from full stock assessments. LBB also presents a new indicator for assessing whether an observed size structure is indicative of a healthy stock. LBB results will obviously be misleading if the length frequency data do not represent the size composition of the exploited size range of the stock or if length frequencies resulting from the interplay of growth and mortality are masked by strong recruitment pulses.

Ecología poblacional de Cittarium pica (Gastropoda: Trochide) en la isla de San Andrés, Reserva Internacional de Biósfera, Seaflower.

Cittarium pica is a conspicuous gastropod of the rocky coastlines of the Caribbean. Given its importance in the diet of Caribbean communities, it has been over-exploited, even reaching extinction in some places, and the species has been included in the red lists of marine invertebrates in some countries. Its fishery in San Andres Island-Colombia is artisanal without any regulation, leading to a decrease in its population. Taking into account the socio-economic, cultural and ecological importance of C. pica and its vulnerability to extinction, it is urgent to develop management actions directed to increase the resilience of the species and its sustainability as a fishery resource. To assess the current population state of C. pica from San Andrés Island, we estimated size structure, sex structure, maturation size, and growth parameters, based on length-frequency data analysis. From September to December 2013, and January to March 2014, we randomly collected 458 individuals at eight representative sites of the rocky shores of the island. We measured the longest diameter of the shell base, determined the sex by the color of the gonad, and thus determined the minimum maturation size. We found, that 80 % of the population consisted of small individuals < 25.5 mm sizes. The sex ratio was 1:1 except in November, where males were more abundant. The minimum size at the beginning of maturity for both sexes was 14.07 mm. The growth parameters of von Bertalanffy: K (0.730 yr-1), L∞ (110.78 mm) and Φ (3.95) were higher when compared to other populations of the Caribbean. The total mortality was 3.39 yr-1, while natural and fishing mortalities were 1.02 yr-1 and 2.36 yr-1, respectively. The maximum annual recruitment pulse was estimated for June, and the maximum exploitation rate for a sustainable yield was between 0.563 and 0.640, when the catch size was greater than 40 mm or 50 mm, respectively. The exploitation rate was estimated in 0.70, suggesting a strong extractive resource pressure. With these results we recommend the closure of the fishery and constant monitoring to promote and the population recovery is verified. Until a monitoring shows that the population recovers on the island.Until a monitoring shows that the population recovers on the island.

Use of the SLW index to calculate growth function in the sea cucumber Isostichopus badionotus.

Age and growth analysis is essential to fisheries management. Indirect methods to calculate growth are widely used; however, length frequency data analysis in sea cucumbers is complicated by high data variability caused by body wall elasticity. Here we calculated Isostichopus badionotus parameters of the von Bertalanffy growth function. In order to address bias produced by body wall elasticity, we compared the performance of four measurements and one compound index that combines different biometric parameters: the square root of the length-width product (SLW). Results showed that variability in length data due to body wall elasticity was controlled by using body length (Le) from the SLW compound index. Growth in I. badionotus follows a negative allometric tendency. Slow or zero growth periods were observed during October and November, when weather conditions were adverse.

Length-based growth, maturity and natural mortality of the cockfish Callorhinchus callorhynchus (Linnaeus, 1758) off Coquimbo, Chile

The growth rate, reproductive aspects, and natural mortality of chimaeras and ratfish are poorly known. In this study, life-history parameters for cockfish Callorhinchus callorhynchus (Holocephali—Callorhin- chidae) are estimated, which is an important fish resource exploited in Chile. Specimens were sampled from the artisanal fishery captures, from November 2006 to November 2007. The standard length (SL) of males fluctuated between 20 and 62 cm, and between 21 and 70 cm for females. Von Bertalanffy growth parameters were estimated through length-frequency data analysis using MULTIFAN. The length-weight relationship and von Bertalanffy growth parameters were significantly different for males and females, as well as the length at 50% maturity. For males a model with 5 age-classes was the best, with asymptotic length L∞=52 cm SL, growth coefficient K=0.473 yr −1 ,a nd age at length zero t0=−0.690 yrs. For females the best model was represented by 10 age-classes (L∞=70.3 cm SL, K=0.193 yr −1 , t0=−1.158 yrs) in the length- frequency data sets. Length at 50% maturity of males was estimated in 43.7 cm SL, and in 50.2 cm SL for females. The natural mortality rate fluctuated between 0.42 and 0.82 yr −1 for males and between 0.12 and 0.37 yr −1 for females, depending upon the method used. It is concluded that C. callorhynchus is a species with life- history parameters significantly different between males and females, and such differences should be taken into account in future population dynamics analysis.

Distribution and ecology of Chaenocephalus aceratus (Channichthyidae) around South Georgia and Shag Rocks (Southern Ocean)

Chaenocephalus aceratus (Family Channicthyidae) is one of the dominant species of demersal fish living on the South Georgia shelf where it is caught in low numbers as by-catch in the mackerel icefish and Antarctic krill commercial fisheries. Data collected during 14 demersal fish surveys, from 1986 to 2006, are analysed to investigate biomass, distribution, growth and diet. Biomass estimates from a swept area method ranged from 4,462 to 28,740 tonnes on the South Georgia and Shag Rock shelves although few fish were caught at Shag Rocks. Analysis of length frequency data indicated that growth was fast in the first five years with males and females attaining lengths at first spawning of 440 mm TL and 520 mm TL. The diet was comprised of fish and crustaceans, with an ontogenetic shift in diet from Euphausia superba and mysids to benthic fish and decapods observed to begin at 250 mm TL. In larger fish (>500 mm TL) the diet was dominated by fish. C. aceratus diet is sufficiently different from the other species of channichthyids around South Georgia to suggest that these species have undergone resource partitioning.

Age and growth of the naticid gastropod Polinices pulchellus (Gastropoda: Naticidae) based on length frequency analysis and statolith growth rings

In Red Wharf Bay, UK the naticid gastropod, Polinices pulchellus, was more abundant and more highly aggregated during the summer months (June–August 2001) than during the winter (December 2000). Whilst small numbers of juvenile P. pulchellus (4–6 mm shell length) were present throughout the year the population consisted mainly of individuals of 12–14 mm shell length. Juvenile snails grew rapidly in size during the winter and early spring; growth then virtually ceased between May and June, following which there was a further period of rapid growth between August and February. Densities ranged between 57 and 4,073 ha−1 and the largest individual collected during this investigation measured 16.2 mm in shell length. Statoliths from adult P. pulchellus revealed the presence of a settlement ring and two prominent growth rings (rings 1 and 2). A curvilinear relationship exists between statolith diameter and shell length in snails up to 16 mm in length. Settlement rings ranged in diameter from 19.7 to 45.2 μm (mean 29.8 μm; SE=0.41) giving an estimated shell length of the settled juvenile of 1.1 mm. The diameter of ring 1 and ring 2 were significantly correlated indicating that rapid growth during the first year is maintained during year 2. Shell lengths estimated from the diameters of the prominent statolith rings and those obtained from length frequency data analysis (LFDA), were broadly congruent strongly suggesting an annual periodicity to the statolith rings. The largest snails (>15 mm) present within this population were estimated to be between 2 and 3 years old. Von Bertallanfy seasonal growth curves obtained from the LFDA predicted values of L∞, K and t 0 of 14.32 mm, 1.54 and −0.14 years, respectively, suggesting that P. pulchellus rapidly attains its maximum asymptotic size.

Changes in growth of juvenile southern bluefin tuna (Thunnus maccoyii): an analysis of length-frequency data from the Australian fishery

Modal analysis is applied to historical length–frequency records of the Australian southern bluefin tunafishery, in order to quantify the variation in mean length from year to year. In the South Australian fishery in the first half of March, the mean length has ranged between 54 cm and 64 cm for 1-year-old fish, 73 cm and 85 cm for 2-year-old fish, and 85 cm and 100 cm for 3-year-old fish. The mean lengths of 2-, 3- and 4-year-old fish, and the increment from age 1 to age 3, have increased substantially over the history of the fishery. This increase in growth is probably a response to a decline in the population due to heavy fishing. In many years in the Western Australian fishery, two or more groups of 1-year-old fish were found: the mean lengths of these groups typically differed by 10 cm. Growth rates also varied markedly according to the season of the year.

Effect of individual variability on estimation of population parameters from length-frequency data

We consider estimation of mortality rates and growth parameters from length-frequency data of a fish stock when there is individual variability in the von Bertalanffy growth parameter Linfinity and investigate the possible bias in the estimates when the individual variability is ignored. Three methods are examined: (i) the regression method based on the Beverton and Holt's (1956, Rapp. P.V. Reun. Cons. Int. Explor. Mer, 140: 67-83) equation; (ii) the moment method of Powell (1979, Rapp. P.V. Reun. Int. Explor. Mer, 175: 167-169); and (iii) a generalization of Powell's method that estimates the individual variability to be incorporated into the estimation. It is found that the biases in the estimates from the existing methods are, in general, substantial, even when individual variability in growth is small and recruitment is uniform, and the generalized method performs better in terms of bias but is subject to a larger variation. There is a need to develop robust and flexible methods to deal with individual variability in the analysis of length-frequency data.

Occurrence of Zebra Mussels in Near-shore Areas of Western Lake Erie

We measured biomass, percent coverage, and length-frequency of zebra mussels in near-shore areas of western Lake Erie between 16 September and 10 November 1993 as part of a larger study on the ecological relationship between diving ducks and zebra mussels. Wet weight biomass of zebra mussels, determined by SCUBA diving, ranged from 0 to 3,611 g/m 2 and averaged ( ± 1 SE) 1,270 ± 380 g/m 2 (n = 11). Percent coverage of lake bottom by zebra mussels ranged from 0 to 70% and averaged 17 ± 4.0% (n = 27). Percent coverage of zebra mussels was relatively high in the northern portion (28–70% coverage) and in the southwestern portion (18–40%), but relatively low ( < 5%) in the southeastern portion of the study area. Percent coverage by zebra mussels, determined from underwater videography, was highly correlated (r 2 = 0.96) with zebra mussel biomass. Analysis of length-frequency data indicated that there was prominent recruitment of juvenile zebra mussels at only three of eight sites. Average shell length ranged from 11 mm to 15 mm at the other five sites. The non-uniform distribution of zebra mussels, as determined from biomass and videography, may have important ramifications when assessing zebra mussel impacts on waterfowl. These data may also be used when assessing impact of zebra mussels on other aquatic organisms in the near-shore areas of western Lake Erie.

Life history strategies of the squid,Illex illecebrosus,in the Northwest Atlantic

Resume Time series (1965-1985) of lllex illecebrosus catch and morphomctric data from the Northwest Atlantic were analysed to describe geographic variability in population structure. The areas studied were NAFO sub-areas 3 to 6, which range from Newfoundland to the northeastern USA shelf. Population components, reflecting seasonal spawning groups, were identified based on analysis of length frequency data. Components 3 and 4 represent two prominent life cycles: the summer spawners and winter spawners respectively. Components 1, 2, and 5 do not represent different life cycles, but result from the capacity to shift between life cycles by prolonging (or shortening) the life span. The presence of up to five components in the southern area illustrates a life history strategy involving protracted spawning and complex population structure. There was clear geographic variability in annual catch, with fluctuations being most extreme in the most northem area. Annual catch levels in al1 areas were significantly correlated with the abundance of the winter-spawning component, as represented by the number of squid within samples which belong to component 4. Population structure in the most northem area was simplest and catch levels therefore were most dependent on the highly migratory winter-spawning component. This leads to greater catch variability in the most northern area than in the other areas. The advantages of good feeding conditions may compensate for the risks associated with long-range migrations, especially recruitment failure. Life history strategies involving migratory and non-migratory population components limit the risk of recruitment failure. The overall resultant life history strategy for Illex illecebrosus is one that ensures survival of the species by stabilizing recruitment in at least one (southern) area through protracted spawning, complex population structure and interaction of spawning components.

Age and Growth of Labeo gonius (Cyprinidae) in Kali River, Uttar Pradesh, India

Studies on the age and growth of Labeo gonius (Cyprinidae) collected from the River Kali, Uttar Pradesh, India, were made by analysis of the annuli found on the scales and through analysis of length-frequency data. A straight line relationship was observed between the scales and body length as expressed by the following equation: Y = -1.2127 + 1.0850 X. The fish attained mean lengths of 14.2, 20.6, 23.9, 26.4, 28.5 and 30.0 cm at the ages of I, II, III, IV, V and VI years, respectively. The growth of the species in cm could be expressed by the von Bertalanffy growth equation as: Lt = 45{1-exp-(-0.21 (t-t0))). Some observations on seasonality of growth are presented.

Current and future trends in fisheries stock assessment and management

There are currently three dominant approaches to fisheries stock assessment: analysis of catch-at-age data; simple models of biomass dynamics (often called surplus production models) that rely only on catch and some index of abundance; and analysis of length frequency data. A key characteristic of all these methods is that they rely primarily on one type of data and ignore most of what is known about the biology of the species in question and what has been learned from fisheries elsewhere. Other information is sometimes included subjectively after the stock assessment is complete. The first major trend in assessment methods is developing ways of incorporating all that is known about the biology of a species into a single unified assessment procedure. The second major development is in methods of incorporating uncertainty in stock assessment, using statistical decision theory. At present few agencies have formal methods for treating the uncertainty inherent in stock assessment, and therefore uncertainty is often ignored. A number of trends in fisheries management are reviewed, including adoption of formal harvest strategies, recognition that fisheries management is a matter of decision-making and risk-taking, and the use of Monte-Carlo evaluation of fisheries management options. Future trends in stock assessment and management will likely include more attention to the behaviour of fishermen in response to regulations, more involvement of user-groups in decision-making, much more allocation of property rights, including complete privatization of some fisheries, and demand for evaluation of cost effectiveness of research and management activities. Threats to commercial fisheries as now known are discussed, including growing allocation to recreational and aboriginal users, environmentalists and the impact of aquaculture.

Growth in Tropical Cephalopods: An Analysis Based on Statolith Microstructure

Validated size-at-age data are presented for two tropical squid species (Loliolus noctiluca and Loligo chinensis) and a sepioid (Idiosepius pygmaeus). Estimates of age were obtained from daily increments in the statolith. All species reached adult size in less than 200 d. For each species, growth in mantle length was linear over the sizes sampled. In L. chinensis, growth was fastest during December–January (summer), with males showing faster growth rates than females. For I. pygmaeus, females generally had a higher growth rate than males. The slowest growth rates for both sexes occurred in the August–September (winter) period. The size-at-age data indicated rapid linear or exponential growth and a short life span of less than 1 yr. In contrast, growth curves generated from analysis of length frequency data (ELEFAN software package) suggested an asymptotic growth curve and ages in excess of 3 yr, and such analyses therefore appear inappropriate. The results of this study and a review of the literature revealed that rapid growth and short life span is the norm for pelagic cephalopods, with tropical species growing considerably faster than their temperate counterparts.

Age, growth and natural mortality rates of some cichlid fishes of Lake Malawi

The growth rates, lengths at maturity, fecundity and natural mortality of several cichlids of importance in trawl catches in Lake Malawi are described. Growth rates were determined by analysis of length frequency data from trawl catches. The breeding season for each species was determined by monthly examination of the gonads, and fecundity determined by egg counts from ripe ovaries. Lengths at maturity were calculated from the proportion of mature fish during breeding seasons. Natural mortality rates were determined from length frequency data from an unfished area of the lake. Values of the growth constant K ranged from 0.487 to 0.671. The ratio of length at maturity to asymptotic length varied from 0.56 to 0.82. Growth parameters are compared with those of other cichlids. Most species mature in their third year. Fecundity was proportional to the square of the length in four of the five species. The species studied appeared to produce only one batch of eggs per breeding season. Instantaneous natural mortality rates ranged from 0.92 to 1.69.

Population Studies on the Toheroa, Amphidesma ventricosum Gray (Eulamellibranchiata)

The ecology, distribution, and commercial importance of the toheroa, Amphidesma ventricosum Gray, are discussed. The habitat favoured by that portion of the population at present known is a beach fully exposed to heavy surf, with a fine sand and sufficient residual moisture to prevent desiccation at low tide. Frequent dense blooms of phytoplankton are necessary to provide an adequate food supply. Estimates of numerical abundance for various beaches are given, showing that violent fluctuations in numbers may occur, sometimes, but not always, with epidemic mortalities. The sampling technique for estimat- ing numerical abundance is described and discussed. The growth rate has been estimated for several different beaches, both by interpreting the annual growth-rings of the shell, and by analysis of length frequency data. The South Island toheroa have a significantly lower growth rate than those in the North Island. It is shown that the distribution of age classes on the beach is inconsistent with the assumption that the species is confined to the littoral region. In particular, the younger toheroa are almost invariably fewer in numbers than would be expected in a self-contained popula- tion. From this, and from the extreme fluctuations in numbers which occur from time to time, it is concluded that some part of the population is located in the sublittoral. The spatial distribution of the beach toheroa shows a high degree of over-dispersion (or aggregation) which is mainly attributable to variations in environmental conditions. Vertical and horizontal zonation of size groups may sometimes occur, but the contributing factors are obscure. Statistical aspects are discussed in appendices.