Differences In Size Selection Research Articles

Feasibility of Redo-Transcatheter Aortic Valve Replacement in Sapien Valves Based on In Vivo Computed Tomography Assessment.

Our aim was to assess the feasibility of repeat transcatheter aortic valve (TAV) replacement for degenerated Sapien3 (S3) prostheses by simulating subsequent implantation of S3 or Evolut, using in vivo computed tomography-based sizing and the impact on coronary and patient-prosthesis mismatch risks. Computed tomography scans from 356 patients with prior S3 TAV replacement implantation were analyzed. The in vivo sizing for second TAV based on averaged area of 3 levels of outflow, mid (narrowest) and inflow, was compared with in vitro recommendations, that is, same size as index S3 for second S3 and 1 size larger for Evolut. Risks of coronary obstruction and patient-prosthesis mismatch were determined by valve-to-aorta distance and estimated effective orifice area, respectively. Overall, the majority of patients (n=328; 92.1%) had underexpanded index S3 with an expansion area of 94% (91%-97%), leading to significant differences in size selection of the second TAV between in vivo and in vitro sizing strategies. Expansion area <89% served as a threshold, resulting in 1 size smaller than the in vitro recommendations were selected in 45 patients (13%) for S3-in-S3 and 13 (4%) for Evolut-in-S3, while the remaining patients followed in vitro recommendations (P<0.01, in vivo versus in vitro sizing). Overall, 57% of total patients for S3-in-S3 simulation and 60% for Evolut-in-S3 were considered low risk for coronary complications. Deep index S3 implantation (odds ratio, 0.76 [interquartile range, 0.67-0.87]; P<0.001) and selecting Evolut as the second TAV (11% risk reduction in intermediate- or high-risk patients) reduced coronary risk. Estimated moderate or severe patient-prosthesis mismatch risk was 21% for S3-in-S3 and 1% for Evolut-in-S3, assuming optimal expansion of the second TAV. Redo-TAV replacement with S3-in-S3 and Evolut-in-S3 could be feasible with low risk to coronaries in ≈60% of patients, while the remaining 40% will be at intermediate or high risk. The feasibility of redo-TAV replacement is influenced by sizing strategy, type of second TAV, native annular anatomy, and implant depth.

Leveraging Delta Smelt Monitoring for Detecting Juvenile Chinook Salmon in the San Francisco Estuary

Monitoring is an essential component in ecosystem management, and leveraging existing data sources for multiple species of interest can be one effective way to enhance information for management agencies. Here, we analyzed juvenile Chinook Salmon (Oncorhynchus tshawytscha) bycatch data that has been collected by the recently established Enhanced Delta Smelt Monitoring program (EDSM), a survey designed to estimate the abundance and distribution of the San Francisco Estuary’s (estuary) endangered Delta Smelt (Hypomesus transpacificus). Two key aspects of the EDSM program distinguish it from other fish surveys in the estuary: a stratified random sampling design and the spatial scale of its sampling effort. We integrated the EDSM data set with other existing surveys in the estuary, and used an occupancy model to assess differences in the probability of detecting Delta Smelt across gear types. We saw no large-scale differences in size selectivity, and while detection probability varied among gear types, cumulative detection probability for EDSM was comparable to other surveys because of the program’s use of replicate tows. Based on our occupancy model and sampling effort in the estuary during spring of 2017 and 2018, we highlighted under-sampled regions that saw improvements in monitoring coverage from EDSM. Our analysis also revealed that each sampling method has its own benefits and constraints. Although the use of random sites with replicates, as conducted by EDSM, can provide more statistically robust abundance estimates relative to traditional methods, the use of fixed stations and simple methods such as beach seining may provide a more cost-effective way to monitor salmon occurrence in certain regions of the estuary. Leveraging the strengths of each survey’s method can enable stronger inferences on salmon abundance and distribution. Careful consideration of these trade-offs is crucial as the management agencies of the estuary continue to adapt and improve their monitoring programs.

Leveraging Delta Smelt Monitoring for Detecting Juvenile Chinook Salmon in the San Francisco Estuary

Monitoring is an essential component in ecosystem management, and leveraging existing data sources for multiple species of interest can be one effective way to enhance information for management agencies. Here, we analyzed juvenile Chinook Salmon (Oncorhynchus tshawytscha) bycatch data that has been collected by the recently established Enhanced Delta Smelt Monitoring program (EDSM), a survey designed to estimate the abundance and distribution of the San Francisco Estuary’s (estuary) endangered Delta Smelt (Hypomesus transpacificus). Two key aspects of the EDSM program distinguish it from other fish surveys in the estuary: a stratified random sampling design and the spatial scale of its sampling effort. We integrated the EDSM data set with other existing surveys in the estuary, and used an occupancy model to assess differences in the probability of detecting Delta Smelt across gear types. We saw no large-scale differences in size selectivity, and while detection probability varied among gear types, cumulative detection probability for EDSM was comparable to other surveys because of the program’s use of replicate tows. Based on our occupancy model and sampling effort in the estuary during spring of 2017 and 2018, we highlighted under-sampled regions that saw improvements in monitoring coverage from EDSM. Our analysis also revealed that each sampling method has its own benefits and constraints. Although the use of random sites with replicates, as conducted by EDSM, can provide more statistically robust abundance estimates relative to traditional methods, the use of fixed stations and simple methods such as beach seining may provide a more cost-effective way to monitor salmon occurrence in certain regions of the estuary. Leveraging the strengths of each survey’s method can enable stronger inferences on salmon abundance and distribution. Careful consideration of these trade-offs is crucial as the management agencies of the estuary continue to adapt and improve their monitoring programs.

Performance of Bycatch Reduction Devices in the Small-Scale Shrimp Trawl Fishery of the Persian Gulf

High rates of discards have been noted for shrimp fisheries worldwide and especially for the small-scale shrimp trawl fisheries of the Persian Gulf. Bycatch reduction devices (BRDs) can significantly decrease discards in shrimp trawl fisheries. We tested the performance of a square mesh panel BRD (SMP) and a juvenile and trash fish excluder device (JTED) in the small-scale shrimp trawl fishery of the Persian Gulf. Efficiency of the BRDs was determined in terms of shrimp loss, by-product loss, the reduction in discards by weight and differences in size selectivity of commercial fishes. Where a JTED was used, reductions in catch, by weight, were (mean ± 95% CI) 12% ± 2.35 for shrimp, 31.9% ± 5.22 for by-product fish and 49% ± 7.52 for discards. Similar reductions were observed when a SMP was used: 16% ± 4.19, 38.3% ± 6.41 and 45% ± 6.15 for shrimp, by-product and discards, respectively. There was no significant difference in the exclusion rate of discards between the JTED and SMP. Significant difference was found for loss of shrimp between JTED and SMP. The mean escapement rate for by-product species in trawl net with JTED and SMP were 35% and 40%, respectively. Selectivity curves of both BRDs indicated, that for each species, the length of 50% retention probability (L50) were smaller than the length at maturity (LM) and an increase in bar spacing in JTED and mesh opening in SMP would be required to delay capture until fish had reached Lm. The results indicated that SMP allows a higher proportion of sub-legal by-product species to escape the trawl, compared to the JTED used in the study. Implementing BRD requirements for the Persian Gulf small-scale shrimp fisheries would contribute to meeting strict sustainability criteria, a good outcome for this small-scale fishery.

Reconciling conflict between the direct and indirect effects of marine reserve protection

SUMMARYNo-take marine reserves directly promote the recovery of predatory species, which can have negative indirect effects on prey populations in reserves. When harvesting also occurs on prey species there is potential conflict between the direct and indirect effects of protection, and reserves may not have conservation benefits for prey species. For example, sea urchins are fished in many regions, but may decline in reserves due to increased predation rates. To investigate this potential conflict, this paper compares density, size, biomass and reproductive potential of both a harvested and an unharvested urchin species between a long-term reserve and unprotected sites in California. Consistent with density-mediated indirect interactions, densities of the unharvested species were 3.4-times higher at unprotected sites compared to reserve sites. However, for the harvested species, densities were comparable between reserve and unprotected sites. Both species were consistently larger at reserve sites, and the biomass and reproductive potential of the harvested species was 4.8- and 7.0-times higher, respectively, than at unprotected sites. This is likely due to differences in size-selectivity between harvesting and predators, and potential compensatory effects of predators. While the generality of these effects needs to be tested, these results suggest mechanisms whereby reserves can benefit both predator and prey species.

Adhesive-based selection by a tentacle-feeding polychaete for particle size, shape and bacterial coating in silt and sand

We tested particle selection by a surface deposit-feeding, tentaculate spionid polychaete, Pseudopolydora kempi japonica Imajima and Hartman. In experiments with peroxide-cleaned, sizegraded but otherwise natural silts and sands, individual worms showed peak preference for particles 80‐99 mm in diameter, compared with previous (Self and Jumars, 1988) documentation of peak preference for particles of 7 mm in experiments conducted with plastic and glass beads. These results imply that microtektites will not in general be good tracers of mixing of mineral grains of comparable size. Animals exhibited statistically signie cant but not marked differences in size selectivity for subrounded versus subangular grain shapes; the size preference peak was broader in subangular grains, for which orientation of the grain can alter probabilities of both contact and retention. When one size class of grains was coated with the bacterium Halomonas halodurans (ATCC 29686), animals in general showed enhanced selection (relative to controls with no food value on any size class) of that size and smaller grains, even though these smaller grains lacked food value. Greatest selection, however, generally occurred for the coated size class. Results frominclusion of glass beads in some of the experiments and from separate experiments with tentacle analogs imply that this selective capability may be largely passive and mechanical. Natural grains, due to surface texture, have more surface area for adhesive contact than do smooth glass beads so that larger grains than beads are retained. Bacteria-coated grains, in turn, appear to be picked up preferentially due to adhesion with the bacterial coating; petroleum jelly-coated microscope slides also succeed in selective retention of the size class that is bacterially coated. Substantial selection by adhesiveutilizing deposit feeders apparently can be achieved without investment in complex, time- and energy-consuming sensory systems and behaviors. Experiments with natural grains showed notably more scatter than prior experiments with glass beads, but this difference is consistent with the mechanism. For nonspherical particles, both contact and retention depend on orientation as well as size.

Quantifying the roles of competing static gears: comparative selectivity of longlines and monofilament gill nets in a multi-species fishery of the Algarve (southern Portugal)

Fishing trials with monofilament gill nets and longlines using small hooks were carried out in Algarve waters (southern Portugal) over a one-year period. Four hook sizes of Mustad brand, round bent, flatted sea hooks (Quality 2316 DT, numbers 15, 13, 12 and 11) and four mesh sizes of 25, 30, 35 and 40 mm (bar length) monofilament gill nets were used. Commercially valuable sea breams dominated the longline catches while small pelagics were relatively more important in the gill nets. Significant differences in the catch size frequency distributions of the two gears were found for all the most important species caught by both gears (Boops boops, Diplodus bellottii, Diplodus vulgaris, Pagellus acarne, Pagellus erythrinus, Spondyliosoma cantharus, Scomber japonicus and Scorpaena notata), with longlines catching larger fish and a wider size range than nets. Whereas longline catch size frequency distributions for most species for the different hook sizes were generally highly overlapped, suggesting little or no differences in size selectivity, gill net catch size frequency distributions clearly showed size selection. A variety of models were fitted to the gill net and hook data using the SELECT method, while the parameters of the logistic model were estimated by maximum likelihood for the longline data. The bi-normal model gave the best fits for most of the species caught with gill nets, while the logistic model adequately described hook selectivity. The results of this study show that the two static gears compete for many of the same species and have different impacts in terms of catch composition and size selectivity. This information will be useful for the improved management of these small-scale fisheries in which many different gears compete for scarce resources.

Comparative fixed gear studies in the Cyclades (Aegean Sea): size selectivity of small-hook longlines and monofilament gill nets

Fishing trials with monofilament gill nets and longlines using small hooks were carried out at the same fishing grounds in Cyclades (Aegean Sea) over 1 year. Four sizes of MUSTAD brand, round bent, flatted sea hooks (Quality 2316 DT, numbers 15, 13, 12 and 11) and four mesh sizes of 22, 24, 26 and 28 mm nominal bar length monofilament gill nets were used. Significant differences in the catch size frequency distributions of the two gears were found for four out of five of the most important species caught by both the gears ( Diplodus annularis, Diplodus vulgaris, Pagellus erythrinus, Scorpaena porcus and Serranus cabrilla), with longlines catching larger fish and a wider size range than gill nets. Whereas longline catch size frequency distributions for most species for the different hook sizes were generally highly overlapped, suggesting little or no differences in size selectivity, gill net catch size frequency distributions clearly showed size selection, with larger mesh sizes catching larger fish. A variety of models were fitted to the gill net data, with the lognormal providing the best fit in most cases. A maximum likelihood method was also used to estimate the parameters of the logistic model for the longline data. Because of the highly overlapped longline catch size frequency distributions parameters could only be estimated for two species. This study shows that the two static gears have different impacts in terms of size selection. This information will be useful for the more effective management of these small-scale, multi-species and multi-gear fisheries.

Influence of the carrier composition on thermal field-flow fractionation for the characterisation of sub-micron polystyrene latex particles

A study on the influence of the carrier composition in a ThFFF system on the retention and thermal diffusion of sub-micron polystyrene latex particles has been carried out. Various factors that may influence retention were studied. These include: the type of electrolyte and surfactant, their respective concentrations, and the addition of an organic modifier. Particle retention is highly sensitive to small changes in the carrier composition. It is demonstrated that under the conditions applied, secondary effects, such as particle–wall and particle–particle interactions, are negligible. Addition of surfactants is required to minimise particle–wall interactions. Generally, retention increases at higher electrolyte concentration. Furthermore, the addition of acetonitrile (ACN) to an aqueous carrier leads also to an increased retention. The type of surfactant as well as its concentration is of influence on the retention time. The three surfactants that were studied, i.e., sodium dodecyl sulfate, Brij 35 and cetyltrimethylammonium bromide, showed significant differences in particle retention behaviour. The observed differences in retention in the carriers can be attributed to actual changes in thermal diffusion. D T appears to be mainly determined by the interaction between the particle’s surface and the carrier liquid, and is therefore highly sensitive to changes in the chemical composition of the particle surface and the carrier. Strong differences in size selectivity were found for different carrier compositions. This allows a relatively easy optimisation of the separation. On the other hand, it complicates the size and composition analysis of particles.

Semi-pelagic longline selectivity for two demersal species from the Azores: the black spot sea bream ( Pagellus bogaraveo) and the bluemouth rockfish ( Helicolenus dactylopterus dactylopterus)

The selectivity of four hook sizes (STELL brand 1 Manufactured by SIAPEL, Setubal, Portugal 1 , Quality 2335, numbers 12, 9, 6 and 4) used in a semi-pelagic longline fishery was studied in the Azores. Two species were caught in sufficient numbers for modelling of selectivity: the black spot sea bream ( Pagellus bogaraveo) and the bluemouth rockfish ( Helicolenus dactylopterus dactylopterus). A maximum likelihood method was used to fit a versatile model which can be used to describe a wide range of selectivity curves; from bell-shaped to asymptotic. Significant differences in size selectivity between hooks were found for both species. In the case of Pagellus bogaraveo, the smallest hook (number 12) had the lowest catch rates and all hooks were characterised by logistic-type selectivity curves, with sizes at 50% selectivity of: 27.9, 30.4, and 32.8 cm for hooks numbers 12, 9 and 6, respectively. The number 9 hook was the most efficient for Helicolenus d. dactylopterus, with selectivity curves varying from strongly skewed to the right for the number 12 hook to logistic-type for the numbers 6 and 4 hooks. Sizes at 50% selectivity for this species were 16.8, 18.7, 20.7, and 22.0 cm, respectively.

Species and size selectivity in a Portuguese multispecies artisanal long-line fishery

The species and size selectivity of long-lines using small hooks were studied off the south coast of Portugal using “Mustad” brand round bent, flatted sea hooks (Quality 2316 DT) numbers 15, 13, and 11 baited with razor shell clam (Ensis siliqua). Hook numbers 13 and 11 are 49 and 109% larger respectively than number 15 hooks in terms of overall size (maximum width × maximum length). A total of 39 900 hooks were fished in 45 sets and 35 species of fish and cephalopods were caught. As a group, 13 species of sea breams (Sparidae) dominated the catch by numbers (58%) and weight (73%). Six species of sea breams, along with the greater weever fish (Trachinus draco) accounted for 81% of the total catch by weight, with the common or white sea bream (Diplodus sargus) being the most important (29%). Catch size distributions by hook size were, in general, highly overlapped for all species and hook size had little apparent effect on minimum size at capture. All hooks caught a wide range of sizes per species, but the catch rate (number of fish per 100 hooks) was significantly lower for the largest hook. Except for the black sea bream (Spondyliosoma cantharus), capture of illegally sized or immature fish was minimal. Small increases in average size with hook size were evident for four species: Diplodus sargus, D. vulgaris, Lithognathus mormyrus and Serranus cabrilla. No differences in size selectivity were detected for Boops boops, D. annularis, Spondyliosoma cantharus and Trachinus draco. A skew-normal model adequately described differences in size selectivity in five of six species.

The foraging ecology of the Gulf of Mexico stone crab Menippe adina (Williams et Felder)

Laboratory experiments were used to study prey species and size selection by the Gulf of Mexico stone crab Menippe adina (Williams et Felder) on oysters, i.e., Crassostrea virginica Gmelin and southern oyster drills Stramonita ( Thais) haemastoma Grey. Stone crabs select smaller rather than larger oyster drills, and smaller rather than larger oysters. Two results support the idea that size selection in this crab is more the result of mechanical limitations to feeding on large prey than active choice for smaller prey. First, differences in size selection disappear when feeding rates are weighted by differences in handling times, which increase with prey size. Second, an estimate of prey value (tissue dry mass divided by handling time) does not differ dramatically with prey type or size, suggesting large variations in handling time obscure differences in prey energy content. Stone crabs select small oysters over small oyster drills. Stone crabs attack larger oyster drills more frequently than small oyster drills, and persist longer before rejecting them as prey. Neither attack frequency nor persistence increase significantly with increasing oyster size. We also studied aggressive interactions between stone crabs provided with oysters as prey and found that larger stone crabs had greater feeding rates than smaller crabs, and exhibited higher frequencies of dominant behaviors. Our results suggest that the relative importance of active choice vs. mechanical limitations in determining prey selection varies with the specific crab predator-prey system. Gulf of Mexico stone crabs may also affect oyster and oyster drill populations by selectively removing smaller individuals. Finally, smaller stone crabs may be forced to forage in suboptimal habitats, or at suboptimal times, by larger, more aggressive conspecifics.

Exploitation of Walleye (Stizostedion vitreum vitreum) in Lac Des Mille Lacs, Northern Ontario, by Commercial and Sport Fisheries, 1958–75

Harvests by three types of gear from Lac des Mille Lacs showed considerable differences in size selection of walleye (Stizostedion vitreum vitreum). Angling gear was most selective for smaller walleye (primarily 4–6 years old) and commercial gill nets and trap nets were most selective for larger walleye (primarily 5–11 years old), indicating there was not effective competition for fish of the same size. The great difference in size selectivity of the gears should serve as a caution against basing inferences about the status of stocks based on harvest from a single or similar gear.From 1971 to 1975 the total annual harvest (5.24 kg/ha) exceeded the theoretical potential yield (3.91 kg/ha) by 34%.The large number of age-groups (1–12), the high sport fishery catch per unit of effort (0.40 fish per man-hour) and the lack of appreciable change in rate of growth suggested no inimical effects on the walleye fishery due to exploitation.Walleye accounted for 62% of the total harvest (1971–75) reflecting both the preference for this species and their vulnerability to conventional (passive) commercial gear. The sport fishery harvest for the same period accounted for 92% of the total harvest. Key words: Percidae, exploitation, Stizostedion, gear selectivity