Initial Size Classes Research Articles

Fluted giant clam (Tridacna squamosa) restocking experiment in an urban turbid reef environment

Abstract Giant clam populations in Singapore are endangered due to historical exploitation, habitat loss, and sediment pollution. Transplanting cultured giant clams onto reefs is a potential conservation strategy. This study examined the growth and survival of three initial size classes (50.0–60.0 mm, 60.1–70.0 mm, >70 mm) of cultured juvenile fluted giant clams, Tridacna squamosa, transplanted to three reef sites under two caging treatments (caged and uncaged). After 145 days, there was no significant difference in clam survival within the size classes and within caging treatments across reef sites, even though environmental conditions varied greatly between sites. However, there was a significant effect of initial size class on T. squamosa survival, with higher survival with increasing size class (50.0–60.0 mm: 11.1%; 60.1–70.0 mm: 34.1%; >70.0 mm: 46.9%). Clams in caged treatments had significantly lower survival (16.7%) than uncaged clams (43.1%), likely due to biofouling atop caged treatments reducing light availability. Growth rates in the caged treatment (2.2 ± SD 1.8 mm month−1) were also lower than those in the uncaged treatment (3.9 ± SD 2.2 mm month−1). By optimizing transplant procedures for Singapore's turbid reef conditions, T. squamosa restocking efforts could play an important role in boosting local population numbers to facilitate natural recovery.

Survival and sexual maturity of sexually propagated Acropora verweyi corals 4 years after outplantation

Most coral reef restoration efforts are carried out over 1–2 years, and few have assessed long‐term (over 3 years) outcomes. Although studies of outplantation of sexually propagated corals have reported promising initial results, few studies have followed outplanted corals to maturity. Here, we monitored sexually propagated Acropora verweyi corals for 4 years post‐outplantation to determine their survival and sexual maturity. These corals were outplanted when 4 months old in two size classes (small = 0.3–0.5 cm; large = 1.0–1.5 cm) at two sites in the northwestern Philippines. Four years after outplantation, the 240 colonies of A. verweyi exhibited 17.9% survival, with mean diameters ranging from 7.48–26.8 cm. Most of the surviving outplants were gravid (81.4% of the 43 colonies) with mean diameters of at least 11.8 cm. Higher survivorship was detected in the initial large size class outplants than in the small ones at the natal site, but not at the other site. However, 4 years after outplantation, there was no significant difference in terms of geometric mean diameter between the initial size classes or between the sites. Results show that 4‐month‐old outplants of sexually propagated corals can survive until sexual maturity and are already capable of contributing gametes for the potential recovery of degraded coral communities at age 4 years.

Nursery culture of sandfish Holothuria scabra in sea-based floating hapa nets: Effects of initial stocking density, size grading and net replacement frequency

Sea-based culture of early juvenile sandfish Holothuria scabra up to fingerling size (>2 g) using floating hapa nets has been confirmed as a viable nursery system in tropical countries such as the Philippines. However, production can be further optimized through more efficient rearing practices. In this study, we demonstrate the effects of initial stocking density, size grading and net replacement frequency during the culture of early juvenile sandfish in sea-based floating hapa nets (2 × 1 × 1 m). Testing different initial stocking density treatments ranging from 150 to 2000 early juveniles (4–10 mm; 0.02–0.06 g) per hapa net, we confirmed significantly faster growth (0.06–0.08 g d−1) and higher survival (72–97%) in low densities (≤500 hapa−1), compared to high densities (≥700 hapa−1: 0.02–0.04 g d−1; 67–80%). Low density culture can produce 2 g sandfish in about a month, while higher densities will require a 2–3 mo culture period to reach this size. Culture performance following size grading was also compared using three initial size classes (small, 0.05–0.99 g; medium, 1–1.99 g; and large, 2–3 g) and a mixed group (0.05–3.00 g). At 45 d, juveniles in pooled size-graded groups grew significantly faster (0.11–0.13 g d−1) than those in the mixed group (0.01 g d−1). Survival was significantly higher in the medium (85.3%) and large (84.7%) groups, than those in the small (54.4%) and mixed (45.6%) groups. However, size variation was not significantly mitigated by grading during the 45-d culture. Culture performance of sandfish was not significantly enhanced by more frequent net replacement for short-term rearing (30–45 d). Optimal results were gained from an initial stocking density of ≤500 early juveniles (5–10 mm) per floating hapa net which may be cultured in a month, without requiring net replacement and size grading to produce ≥2 g sandfish. However, in cases of high hatchery production, it is also feasible to adopt higher density stocking (e.g. >1000 hapa−1), but will require longer culture duration (60–85 d), monthly net replacement and size-grading to attain the same size. Results of this study can help fine-tune management practices for nursery culture of sandfish in sea-based floating hapa net nurseries in order to boost production of fingerlings needed for aquaculture and restocking.

Establishment of early-stage planted seedlings of a native woody species under a closed canopy of invasive Casuarina equisetifolia in the subtropical oceanic Ogasawara Islands

ABSTRACTExtirpation of invasive plants does not always result in successful restoration of native plant communities because it can alter ecosystem function or promote further incursion of other invasive plants. To test whether seedlings of native plants can become established without extirpating invasive plants, we evaluated the survival and growth of seedlings of a native tree species, Schima mertensiana, planted under closed forest dominated by an invasive species, Casuarina equisetifolia in the Ogasawara Islands, an oceanic archipelago in the western Pacific Ocean. The initial establishment of S. mertensiana is inhibited by the highly accumulated litter of C. equisetifolia; therefore, few seedlings and saplings of S. mertensiana were observed in the forest. We planted seedlings of three initial size classes, and their size parameters (diameter at ground level, height, and number of leaves) were monitored for 69 months. More than 75% of the planted seedlings survived during the study period. There were no significant differences in the number of surviving seedlings among the initial size classes. Steady growth of seedlings was observed regardless of initial size class. Our results indicate that planted S. mertensiana seedlings can survive and grow in forests without removing C. equisetifolia, and provide a case study that shows that planted seedlings of a native woody species can establish under a closed canopy dominated by an invasive woody species, at least for several years.

Projections of glacier change in the Altai Mountains under twenty-first century climate scenarios

We project glacier surface mass balances of the Altai Mountains over the period 2006–2100 for the representative concentration pathway (RCP) 4.5 and RCP8.5 scenarios using daily near-surface air temperature and precipitation from 12 global climate models in combination with a surface mass balance model. The results indicate that the Altai glaciers will undergo sustained mass loss throughout the 21st for both RCPs and reveal the future fate of glaciers of different sizes. By 2100, glacier area in the region will shrink by 26 ± 10 % for RCP4.5, while it will shrink by 60 ± 15 % for RCP8.5. According to our simulations, most disappearing glaciers are located in the western part of the Altai Mountains. For RCP4.5, all glaciers disappearing in the twenty-first century have a present-day size smaller than 5.0 km2, while for RCP8.5, an additional ~7 % of glaciers in the initial size class of 5.0–10.0 km2 also vanish. We project different trends in the total meltwater discharge of the region for the two RCPs, which does not peak before 2100, with important consequences for regional water availability, particular for the semi-arid and arid regions. This further highlights the potential implications of change in the Altai glaciers on regional hydrology and environment.

A Novel Process for the Study of Breakage Energy versus Particle Size

The energy size relationship is examined, either as the specific energy required breaking a particulate material from an initial size d1 to a final size d2, where d is usually the d80 size, or as the specific energy required to break a single particle. The present work uses the results obtained using a controlled frequency centrifugal crusher to crush particles of a predetermined size class under different rotation frequencies related to the kinetic energy of the particles at the moment of crushing. The paper calculates the relationship between the rotation frequency and the kinetic energy of the particles before crushing and examines the size distribution of the products. The study results allow presenting the relationship between the kinetic energy of the particles and the mass of particles produced below the initial size class. The work also produces the optimum mathematical model that describes this relationship among three proposed ones. According to this model one can calculate the energy required breaking half of the initial mass below the initial size class and the corresponding specific energy is appointed to the average size of the class. The parameters of the mathematical model can be used to compare the grindability of the different materials. The process can be used as an alternative to the drop weight technique used so far for the study of the breakage energy of minerals and rocks.

Natural mortality rates in tropical tunas: size really does matter

Important size-related variability in natural mortality rates has been revealed in populations of skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacares), and bigeye tuna (Thunnus obesus) in the western tropical Pacific Ocean using a new, size-structured tagging model. The tagging data were classified into release groups by size at release, and a growth model was used to predict size at each time at liberty interval. Natural and fishing mortality rates were categorized by broad size-classes and estimated by maximum likelihood. The method incorporates a correction for incomplete mixing of new releases. For each population, the natural mortality rate declined by about an order of magnitude over the initial size-classes. For skipjack and yellowfin tuna, there was also evidence of elevated natural mortality for some of the larger size-classes. Size- or age-related variability in natural mortality is likely to have important implications for tropical tuna stock assessment in the western Pacific.

Effects of End of Dry Season Shoot Removal on the Growth of Three Savanna Grasses with Different Phenologies1

BiotropicaVolume 31, Issue 3 p. 430-438 Effects of End of Dry Season Shoot Removal on the Growth of Three Savanna Grasses with Different Phenologies1 Juan F. Silva, Corresponding Author Juan F. Silva Centro de Investigaciones Ecologicas de Los Andes Tropicales (CIELAT). Fac. de Ciencias, Universidad de Los Andes, Mérida. Venezuela.2 Email: jsilva@ciens.ula.ve.Search for more papers by this authorJosé Raventós, José Raventós Centro de Investigaciones Ecologicas de Los Andes Tropicales (CIELAT). Fac. de Ciencias, Universidad de Los Andes, Mérida. Venezuela. Department d'Ecologia, Universitat d'Alacant, Campus de Sant Vicent del Raspeig, Ap. Correus 99, E-03080, Alacant, Spain. Email: jraventos@ua.esSearch for more papers by this author Juan F. Silva, Corresponding Author Juan F. Silva Centro de Investigaciones Ecologicas de Los Andes Tropicales (CIELAT). Fac. de Ciencias, Universidad de Los Andes, Mérida. Venezuela.2 Email: jsilva@ciens.ula.ve.Search for more papers by this authorJosé Raventós, José Raventós Centro de Investigaciones Ecologicas de Los Andes Tropicales (CIELAT). Fac. de Ciencias, Universidad de Los Andes, Mérida. Venezuela. Department d'Ecologia, Universitat d'Alacant, Campus de Sant Vicent del Raspeig, Ap. Correus 99, E-03080, Alacant, Spain. Email: jraventos@ua.esSearch for more papers by this author First published: 15 March 2006 https://doi.org/10.1111/j.1744-7429.1999.tb00385.xCitations: 6 1 Received 14 March 1997; revision accepted 27 April 1998. Read the full textAboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume31, Issue3September 1999Pages 430-438 RelatedInformation

Behavior of a polydisperse cluster of interacting drops evaporating in an inviscid vortex

The dynamics and evaporation of polydisperse collections of liquid drops in an axisymmetric, infinite, cylindrical vortex are described using a statistical model. This model describes both the dense regime where inter-particle effects are important and the dilute regime. The initial size distribution is partitioned into size classes and each initial size-class is followed dynamically and thermodynamically using a class-defined, drop-frame coordinate system. Each initial-size-class develops a continuum of sizes as drops centrifuge towards hotter surroundings and evaporate. A separate coordinate system tracks the gas phase. Because larger drops experience larger centrifugal force, they approach the hotter gas faster. However, for appropriate liquid heating times, the large drops might evaporate at a faster rate, and so the size-differentiated centrifugation previously observed and calculated for cold flow situations does not occur. Instead, a radially peaked drop size distribution is developed in the gas vortex. The centrifugal motion forms a drop-free inner vortex core bound by a cylindrical shell containing all the drops. This shell of gas and drops is called the drop cluster. Numerical calculations show that more parameters control dense clusters than dilute clusters; examples of these parametric relations include: (i the gas vortex, whereas drop size distribution controls the outer region; and (ii increases the maximum mass fraction of the evaporated compound and enhances penetration of the evaporated compound into the surroundings. Except for dilute clusters, the assumption of uniform drop number distribution in the cluster is found to be inappropriate. Instead, the drop size distribution always becomes non-uniform even if the initial size distribution is monodisperse and the initial drop number distribution is uniform. This development of non-uniformity is caused by drops at the cluster peripheries preventing heat conduction/convection to drops in the central cluster.

Effects of Interference from Calamagrostis rubescens on Size Distribution in Stands of Pinus ponderosa

SUMMARY (1) Pinus ponderosa Dougl. was grown as widely-spaced trees in monoculture and in mixture with the grass Calamagrostis rubescens Buckl. for four growing seasons on a forest site in north-western Montana, U.S.A. Interference from C. rubescens reduced biomass production of P. ponderosa. Weights of foliage, of above-ground woody tissue, and of roots were 430%, 450%, and 460% greater in the monoculture than in the mixture. (2) The frequency distribution of stem volumes in the monoculture became positively skewed after two growing seasons. Therefore, dominance and suppression associated with above-ground competition between trees are not necessary for the development of skewed size distributions in stands of P. ponderosa. (3) The size distribution became positively skewed more quickly, and remained more highly skewed, in the mixture than in the monoculture. (4) Interference from C. rubescens decreased the mean growth rate of stem volume in P. ponderosa, regardless of initial size class, but simultaneously increased the relative variation in growth rate. The greater variation in growth rate more than offset the tendency of slower growing stands to have more symmetrical size distributions.

Interactions among factors affecting growth, development and survival in experimental populations of Bufo terrestris (Anura: Bufonidae).

We designed a series of field experiments to investigate the importance of interactions between biotic and abiotic factors on the survival and development of larval cohorts of Bufo terrestris. Five "blocks" in a large pond represented environments of varying physical harshness. In the more severe blocks, increased density inhibited growth rates, yet in the more benign blocks, increased density enhanced growth rate. Although different blocks produced very different levels of survival to metamorphosis and size at metamorphosis, there were no interactions with density. Increased density produced lengthened development times in the harsher blocks, but had no effect in the less stressful blocks. Hatchlings that were in the lowest of 3 initial size classes never caught up with their larger contemporaries and survived poorly. Hatchlings in the middle and largest size classes performed equivalently in all parameters of growth and development, but hatchlings from the middle size class were less likely to survive than their larger contemporaries. The effects of initial size did not interact with block. The inhibitory patterns displayed by density in conjunction with varying physical environments are similar to those found in comparable experiments with plants.