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Size Limits (size + limit)

Distribution by Scientific Domains

Life Sciences	54%
Earth and Environmental Science	27%

Kinds of Size Limits

minimum size limit

Selected Abstracts

Introducing size limits as a management tool for the recreational line fishery of silver kob, Argyrosomus inodorus (Griffiths and Heemstra), in Namibian waters

FISHERIES MANAGEMENT & ECOLOGY, Issue 3 2001
C. H. Kirchner
Individual silver kob Argyrosomus inodorus (Griffiths and Heemstra) first mature at just over 1 yr of age and the median age at maturity is approximately 1.5 yr. Spawning of silver kob was observed in the southern and central region of the stock's range, but little spawning activity was found in silver kob sampled from the northern region. The spawning period is protracted over 6 months (October,March), which coincides with warmer water temperatures (>15 °C) and the occurrence of large-sized spawning silver kob in the southern and central part of Namibia. Implementing a minimum size limit for the silver kob fishery is not recommended as it will have serious economic implications for the coastal communities. The protection of the spawning areas, Meob Bay and Sandwich, should be continued and a strict bag limit on large-sized silver kob is recommended for the Namibian silver kob recreational fishery. [source]

Stocking piscivores to improve fishing and water clarity: a synthesis of the Lake Mendota biomanipulation project

FRESHWATER BIOLOGY, Issue 12 2002
R. C. Lathrop
SUMMARYY 1.,A total of 2.7 × 106 walleye fingerlings and 1.7 × 105 northern pike fingerlings were stocked during 1987,99 in eutrophic Lake Mendota. The objectives of the biomanipulation were to improve sport fishing and to increase piscivory to levels that would reduce planktivore biomass, increase Daphnia grazing and ultimately reduce algal densities in the lake. The combined biomass of the two piscivore species in the lake increased rapidly from < 1 kg ha,1 and stabilised at 4,6 kg ha,1 throughout the evaluation period. 2.,Restrictive harvest regulations (i.e. increase in minimum size limit and reduction in bag limit) were implemented in 1988 to protect the stocked piscivores. Further restrictions were added in 1991 and 1996 for walleye and northern pike, respectively. These restrictions were essential because fishing pressure on both species (especially walleye) increased dramatically during biomanipulation. 3.,Commencing in 1987 with a massive natural die-off of cisco and declining yellow perch populations, total planktivore biomass dropped from about 300,600 kg ha,1 prior to the die-off and the fish stocking, to about 20,40 kg ha,1 in subsequent years. These low planktivore biomasses lasted until a resurgence in the perch population in 1999. 4.,During the period prior to biomanipulation when cisco were very abundant, the dominant Daphnia species was the smaller-bodied D. galeata mendotae, which usually reached a biomass maximum in June and then crashed shortly thereafter. Beginning in 1988, the larger-bodied D. pulicaria dominated, with relatively high biomasses occurring earlier in the spring and lasting well past mid-summer of many years. 5.,In many years dominated by D. pulicaria, Secchi disc readings were greater during the spring and summer months when compared with years dominated by D. galeata mendotae. During the biomanipulation evaluation period, phosphorus (P) levels also changed dramatically thus complicating our analysis. Earlier research on Lake Mendota had shown that Daphnia grazing increased summer Secchi disc readings, but P concentrations linked to agricultural and urban runoff and to climate-controlled internal mixing processes were also important factors affecting summer readings. 6.,The Lake Mendota biomanipulation project has been a success given that high densities of the large-bodied D. pulicaria have continued to dominate for over a decade, and the diversity of fishing opportunities have improved for walleye, northern pike and, more recently, yellow perch. 7.,Massive stocking coupled with very restrictive fishing regulations produced moderate increases in piscivore densities. Larger increases could be realised by more drastic restrictions on sport fishing, but these regulations would be very controversial to anglers. 8.,If the lake's food web remains in a favourable biomanipulation state (i.e. high herbivory), further improvements in water clarity are possible with future reductions in P loadings from a recently initiated non-point pollution abatement programme in the lake's drainage basin. [source]

Using scissors to quantify hardness of insects: do bats select for size or hardness?

JOURNAL OF ZOOLOGY, Issue 4 2007
P. W. Freeman
Abstract Scissors are used to determine the hardness of fresh insects of different size and taxa. Our results indicate a strong relationship between the size of an insect and its hardness, which can be expressed as log(Fmax)=0.65 × log(V)+,. Fmax is the maximal force needed to cut the insect and is our measure of insect hardness. V is the volume of the insect and , is a constant that can be derived for different insect taxa. The value of 0.65 was found as an average of beetle and moth samples, and this number appears consistent across insect taxa. We found that beetles averaged about 3.2 times harder than moths of the same size. Beetles were also more variable in hardness than moths, with the softest beetles about equal in hardness to an average moth of the same size. Using our data on insect hardness coupled with data on the diets of bats and their bite forces from the literature, we attempt to determine whether the upper size limit of insects taken by a bat is limited by the insect's dimensions or its hardness. Our results indicate that both these factors may be important. [source]

The properties of Jovian Trojan asteroids listed in SDSS Moving Object Catalogue 3

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007
Gy. M. Szabó
ABSTRACT We analyse 1187 observations of about 860 unique candidate Jovian Trojan asteroids listed in the 3rd release of the Sloan Digital Sky Survey (SDSS) Moving Object Catalogue. The sample is complete at the faint end to r= 21.2 mag (apparent brightness) and H= 13.8 (absolute brightness, approximately corresponding to 10 km diameter). A subset of 297 detections of previously known Trojans were used to design and optimize a selection method based on observed angular velocity that resulted in the remaining objects. Using a sample of objects with known orbits, we estimate that the candidate sample contamination is about 3 per cent. The well-controlled selection effects, the sample size, depth and accurate five-band UV,IR photometry enabled several new findings and the placement of older results on a firmer statistical footing. We find that there are significantly more asteroids in the leading swarm (L4) than in the trailing swarm (L5): N(L4)/N(L5) = 1.6 ± 0.1, independently of limiting object's size. The overall counts normalization suggests that there are about as many Jovians Trojans as there are main-belt asteroids down to the same size limit, in agreement with earlier estimates. We find that Trojan asteroids have a remarkably narrow colour distribution (root mean scatter of only ,0.05 mag) that is significantly different from the colour distribution of the main-belt asteroids. The colour of Trojan asteroids is correlated with their orbital inclination, in a similar way for both swarms, but appears uncorrelated with the object's size. We extrapolate the results presented here and estimate that the Large Synoptic Survey Telescope will determine orbits, accurate colours and measure light curves in six photometric bandpasses for about 100 000 Jovian Trojan asteroids. [source]

Management and Recovery Options for Ural River Beluga Sturgeon

CONSERVATION BIOLOGY, Issue 3 2010
PHAEDRA DOUKAKIS
caviar; CITES; criadero; Mar Caspio; puntos de referencia; sobrepesca Abstract:,Management of declining fisheries of anadromous species sometimes relies heavily on supplementation of populations with captive breeding, despite evidence that captive breeding can have negative consequences and may not address the root cause of decline. The beluga sturgeon (Huso huso), a species threatened by the market for black caviar and reductions in habitat quality, is managed through harvest control and hatchery supplementation, with an emphasis on the latter. We used yield per recruit and elasticity analyses to evaluate the population status and current levels of fishing and to identify the life-history stages that are the best targets for conservation of beluga of the Ural River. Harvest rates in recent years were four to five times higher than rates that would sustain population abundance. Sustainable rates of fishing mortality are similar to those for other long-lived marine species such as sharks and mammals. Yield per recruit, which is maximized if fish are first harvested at age 31 years, would be greatly enhanced by raising minimum size limits or reducing illegal take of subadults. Improving the survival of subadult and adult females would increase population productivity by 10 times that achieved by improving fecundity and survival from egg to age 1 year (i.e., hatchery supplementation). These results suggest that reducing mortality of subadults and adult wild fish is a more effective conservation strategy than hatchery supplementation. Because genetics is not factored into hatchery management practices, supplementation may even reduce the viability of the beluga sturgeon. Resumen:,El manejo de pesquerías de peces anádromos en declinación a veces depende estrechamente de la suplementación de poblaciones mediante la reproducción en cautiverio, no obstante la evidencia de que la reproducción en cautiverio puede tener consecuencias negativas y no abordar la causa principal de la declinación. El esturión beluga (Huso huso), una especie amenazada por el mercado de caviar negro y por reducciones en la calidad del hábitat, es manejado mediante el control de la cosecha y suplementación de poblaciones, con énfasis en esta. Utilizamos análisis de producción por recluta y de elasticidad para evaluar el estatus de la población y los niveles de pesca actuales y para identificar las etapas de la historia de vida que son los mejores blancos para la conservación del beluga en el Río Ural. Las tasas de cosecha en años recientes fueron cuatro a cinco veces mayores que las tasas que sustentarían la abundancia de la población. Las tasas sustentables de mortalidad por pesca son similares a las de otras especies marinas longevas como tiburones y mamíferos. La producción por recluta, que es maximizada si los peces son cosechados a la edad de 31 años, podría incrementar significativamente elevando los límites de talla mínima o reduciendo la captura ilegal de subadultos. La mejora de la supervivencia de hembras subadultas y adultas incrementaría la productividad de la población 10 veces más que la mejora obtenida incrementando la fecundidad y supervivencia de huevo a 1 año de edad (i. e., suplementación de poblaciones mediante reproducción en cautiverio). Estos resultados sugieren que la reducción de la mortalidad de peces silvestres subadultos y adultos es una mejor estrategia de conservación que la suplementación. Debido a que la genética no es considerada en las prácticas de manejo en los criaderos, la suplementación incluso puede reducir la viabilidad del esturión beluga. [source]

Broadbill swordfish: status of established fisheries and lessons for developing fisheries

FISH AND FISHERIES, Issue 4 2000
P. Ward
Guidelines for the assessment and management of developing swordfish fisheries are derived through an examination of five swordfish fisheries. As they develop, swordfish fisheries may be inclined to local depletion around underwater features, such as seamounts and banks. Few nations have applied the precautionary approach in managing their developing swordfish fisheries. Without controls, swordfish fisheries expand geographically and fishing effort increases, often overshooting optimum levels. However, it is difficult to distinguish clear evidence of fishery collapse; modern longliners harvest widely distributed tuna and swordfish and they are able to relocate to distant areas or switch between target species in response to fluctuations in species abundance and price. Furthermore, the wide distribution of swordfish combined with year-round spawning and high growth rates amongst juveniles probably contribute to the apparent resilience of swordfish stocks to intensive harvesting. Over half the world's swordfish catch is taken as an incidental catch of longliners fishing for tuna. In several areas, such as the North Atlantic, catch quotas have sometimes caused tuna longline fishers to discard swordfish. Minimum size limits have also resulted in discarding of swordfish in tuna fisheries and in dedicated swordfish fisheries. In addition to weakening the effectiveness of those management measures, bycatch and discarding add to the complexities of managing swordfish fisheries and to uncertainties in assessing the stocks. Longliners that target swordfish often fish at high latitudes where interactions with marine wildlife, such as seabird, are generally more frequent than at low latitudes. Concern over incidental catches of marine wildlife and other species is becoming a driving force in the management of several swordfish fisheries. Fishery management organisations will need to implement management measures to protect non-target species and gather reliable data and information on the situation by placing observers on boats fishing for swordfish. [source]

Introducing size limits as a management tool for the recreational line fishery of silver kob, Argyrosomus inodorus (Griffiths and Heemstra), in Namibian waters

An integrated serum proteomic approach capable of monitoring the low molecular weight proteome with sequencing of intermediate to large peptides

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2009
Karen Merrell
The low-abundance, low molecular weight serum proteome has high potential for the discovery of new biomarkers using mass spectrometry (MS). Because the serum proteome is large and complex, defining relative quantitative differences for a molecular species between comparison groups requires an approach with robust separation capability, high sensitivity, as well as high mass resolution. Capillary liquid chromatography (cLC)/MS provides both the necessary separation technique and the sensitivity to observe many low-abundance peptides. Subsequent identification of potential serum peptide biomarkers observed in the cLC/MS step can in principle be accomplished by in series cLC/MS/MS without further sample preparation or additional instrumentation. In this report a novel cLC/MS/MS method for peptide sequencing is described that surpasses previously reported size limits for amino acid sequencing accomplished by collisional fragmentation using a tandem time-of-flight MS instrument. As a demonstration of the approach, two low-abundance peptides with masses of ,4000,5000,Da were selected for MS/MS sequencing. The multi-channel analyzer (MCA) was used in a novel way that allowed for summation of 120 fragmentation spectra for each of several customized collision energies, providing more thorough fragmentation coverage of each peptide with improved signal to noise. The peak list from this composite analysis was submitted to Mascot for identification. The two index peptides, 4279,Da and 5061,Da, were successfully identified. The peptides were a 39 amino acid immunoglobulin G heavy chain variable region fragment and a 47 amino acid fibrin alpha isoform C-terminal fragment. The method described here provides the ability both to survey thousands of serum molecules and to couple that with markedly enhanced cLC/MS/MS peptide sequencing capabilities, providing a promising technique for serum biomarker discovery. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Preservation causes shrinkage in seahorses: implications for biological studies and for managing sustainable trade with minimum size limits

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2009
Julie L. Nadeau
Abstract 1.The implications of shrinkage associated with desiccation and ethanol preservation for seahorses (genus Hippocampus) were investigated using Hippocampus guttulatus (European long-snouted seahorse) as a model. Specifically, this research addressed the implications of preservation for taxonomy and life history studies and the application of minimum size limits (MSL) for managing seahorse trade. 2.In 2004, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) listed all seahorse species on its Appendix II, and recommended a 10,cm MSL as an interim means of ensuring sustainable international trade. Inconsistencies in seahorse measurement methods and repeatability posed challenges for applying the MSL. Moreover, the shrinking effect of desiccation on body length observed in other fish was assumed to be negligible for seahorses because of their high degree of ossification. 3.Changes in seahorse sizes were measured following immersion in ethanol and desiccation. H. guttulatus shrank on average by 0.1,2.3% when preserved in ethanol and 3.0,6.4% when dried, depending on the trait measured. Similar trends were observed in a sample of H. kuda (yellow seahorse). Specimen posture during drying, and measurement methods also influenced estimates of size. 4.Based on the shrinkage observed, 14,44% of captured seahorses that are dried could shrink to below the recommended MSL, even if all seahorses were longer than the MSL at capture. This demonstrates that small changes in body lengths can have significant implications for trade of species managed with size limits. 5.Recommendations are to (1) standardize seahorse measurement methods, (2) consider the effects of preservation and measurement technique on body lengths, and apply appropriate corrections in comparative studies and when developing fisheries management strategies, and (3) adjust size limits at the point of capture to ensure retained seahorses comply with the CITES recommended MSL. Copyright © 2008 John Wiley & Sons, Ltd. [source]