Inshore spawning of cobia (Rachycentron canadum) in South Carolina

We documented inshore spawning of the recreationally important cobia (Rachycentron canadum) in Port Royal Sound (PRS) and St. Helena Sound (SHS), South Carolina, during the period from April to June in both 2007 and 2008. Histological analysis of ovaries confirmed the presence of actively spawning females inshore, and gonadosomatic index (GSI) values from females collected inshore (mean=7.8) were higher than the values from females caught offshore (mean=5.6); both of these mean values indicate that spawning occurred locally. Additionally, we conducted an ichthyoplankton survey in 2008 and found cobia eggs and larvae as far as 10 and 15 km inshore from the mouths of SHS and PRS, respectively. A study of egg development that we conducted in 2007 and 2008 using hatchery-reared cobia eggs provided descriptions of embryological development of cobia. Comparison of visual and quantitative characteristics of the field-collected eggs with those of the hatchery-reared eggs allowed positive identification of eggs collected in plankton samples. The ages of field-collected eggs and presence of females with hydrated oocytes in PRS and SHS observed in our ichthyoplankton survey and histological analysis indicated that wild cobia spawn in the afternoon and early evening. The inshore migration of cobia from April to June, the presence of actively spawning females, significantly higher GSI values, and the collection of eggs inside PRS and SHS all confirm that these estuaries provide spawning habitat for cobia. Because of the potential for heavy exploitation by recreational anglers as cobia move inshore to spawn in South Carolina, current management strategies may require review.

Temporal trends (2000–2011) and influences on fishery-independent catch rates for loggerhead sea turtles (Caretta caretta) at an important coastal foraging region in the southeastern United States

Seasonal trawling was conducted randomly in coastal (depths of 4.6–17 m) waters from St. Augustine, Florida, (29.9°N) to Winyah Bay, South Carolina (33.1°N), during 2000–03, 2008–09, and 2011 to assess annual trends in the relative abundance of sea turtles. A total of 1262 loggerhead sea turtles (Caretta caretta) were captured in 23% (951) of 4207 sampling events. Capture rates (overall and among prevalent 5-cm size classes) were analyzed through the use of a generalized linear model with log link function for the 4097 events that had complete observations for all 25 model parameters. Final models explained 6.6% (70.1–75.0 cm minimum straight-line carapace length [SCLmin]) to 14.9% (75.1–80.0 cm SCLmin) of deviance in the data set. Sampling year, geographic subregion, and distance from shore were retained as significant terms in all final models, and these terms collectively accounted for 6.2% of overall model deviance (range: 4.5–11.7% of variance among 5-cm size classes). We retained 18 parameters only in a subset of final models: 4 as exclusively significant terms, 5 as a mixture of significant or nonsignificant terms, and 9 as exclusively nonsignificant terms. Four parameters also were dropped completely from all final models. The generalized linear model proved appropriate for monitoring trends for this data set that was laden with zero values for catches and was compiled for a globally protected species. Because we could not account for much model deviance, metrics other than those examined in our study may better explain catch variability and, once elucidated, their inclusion in the generalized linear model should improve model fits.

Poroviscoelastic characterization of particle-reinforced gelatin gels using indentation and homogenization.

Hydrogels are promising materials for bioengineering applications, and are good model materials for the study of hydrated biological tissues. As these materials often have a structural function, the measurement of their mechanical properties is of fundamental importance. In the present study gelatin gels reinforced with ceramic microspheres are produced and their poroviscoelastic response in spherical indentation is studied. The constitutive responses of unreinforced gels are determined using inverse finite element modeling in combination with analytical estimates of material parameters. The behavior of composite gels is assessed by both analytical and numerical homogenization. The results of the identification of the constitutive parameters of unreinforced gels show that it is possible to obtain representative poroviscoelastic parameters by spherical indentation without the need for additional mechanical tests. The agreement between experimental results on composite gelatin and the predictions from homogenization modeling show that the adopted modeling tools are capable of providing estimates of the poroviscoelastic response of particle-reinforced hydrogels.

Adjustment of ocean color sensor calibration through multi-band statistics

The band-by-band vicarious calibration of on-orbit satellite ocean color instruments, such as SeaWiFS and MODIS, using ground-based measurements has significant residual uncertainties. This paper applies spectral shape and population statistics to tune the calibration of the blue bands against each other to allow examination of the interband calibration and potentially provide an analysis of calibration trends. This adjustment does not require simultaneous matches of ground and satellite observations. The method demonstrates the spectral stability of the SeaWiFS calibration and identifies a drift in the MODIS instrument onboard Aqua that falls within its current calibration uncertainties.

A sudden collapse in distribution of Pacific sardine (Sardinops sagax) off southwestern Australia enables an objective re-assessment of biomass estimates

Fishery-independent estimates of spawning biomass (BSP) of the Pacific sardine (Sardinops sagax) on the south and lower west coasts of Western Australia (WA) were obtained periodically between 1991 and 1999 by using the daily egg production method (DEPM). Ichthyoplankton data collected during these surveys, specifically the presence or absence of S. sagax eggs, were used to investigate trends in the spawning area of S. sagax within each of four regions. The expectation was that trends in BSP and spawning area were positively related. With the DEPM model, estimates of BSP will change proportionally with spawning area if all other variables remain constant. The proportion of positive stations (PPS), i.e., stations with nonzero egg counts — an objective estimator of spawning area — was high for all south coast regions during the early 1990s (a period when the estimated BSP was also high) and then decreased after the mid-1990s. There was a decrease in PPS from the mid-1990s to 1999. The particularly low estimates in 1999 followed a severe epidemic mass mortality of S. sagax throughout their range across southern Australia. Deviations from the expected relationship between BSP and PPS were used to identify uncertainty around estimates of BSP. Because estimation of spawning area is subject to less sampling bias than estimation of BSP, the deviation in the relation between the two provides an objective basis for adjusting some estimates of the latter. Such an approach is particularly useful for fisheries management purposes when sampling problems are suspected to be present. The analysis of PPS undertaken from the same set of samples from which the DEPM estimate is derived will help provide information for stock assessments and for the management of purse-seine fisheries.

Age, growth, and reproduction of permit (Trachinotus falcatus) in Florida waters

We examined 536 permit (Trachinotus falcatus, 65–916 mm FL) collected from the waters of Florida Keys and from the Tampa Bay area on Florida’s Gulf coast to describe their growth and reproduction.Among permit that we sexed, females ranged from 266 to 916 mm in length (mean=617) and males ranged from 274 to 855 mm (mean=601). Ages of 297 permit ranging from 102 to 900 mm FL were estimated from thin-sectioned otoliths (sagittae). The large proportion of otoliths with an annulus on the margin and an otolith from an OTC-injected fish suggested that a single annulus was formed each year during late spring or early summer.Permit reach a maximum age of at least 23 years.Permit grew rapidly until an age of about five years, and then growth slowed considerably. Male and female von Bertalanffy growth models were not significantly different, and the sexes-combined growth model was FL=753.1(1–e –0.348(Age+0.585)). Gonad development was seasonal, and spawning occurred during late spring and summer over artificial and natural reefs at depths of 10–30 m. Ovaries that contained oocytes in the final stages of oocyte maturation or postovulatory follicles were found during May–July. We estimated that 50% of the females in the population had reached sexual maturity by 547 mm and an age of 3.1 years and that 50% of the males in the population had reached sexual maturity by 486 mm and an age of 2.3 years. Because Florida regulations restrict the maximum size of permit caught in recreational and commercial fisheries to 20-inch (508-mm), most fish harvested are sexually immature. With the current size selectivity of the fishery, the spawning stock biomass of permit could decrease quickly in response to moderate levels of fishing mortality; thus, the regulations in place in Florida to restrict harvest levels appear to be justified.

白皮松花粉管发育过程中RNA、蛋白质和多糖类物质的合成及其动态变化

花粉管是有花植物受精过程中雄性生殖单位的载体，它同根毛、真菌菌丝一样，具有典型的极性顶端生长模式。裸子植物花粉与被子植物相比，具有萌发时间较长，生长缓慢等特点。但是目前人们对于裸子植物花粉萌发和花粉管生长的机理还不清楚。本文以裸子植物白皮松（Pinus bungeana）的花粉为材料，采用细胞学和生理生化方法，包括应用普通光学显微镜、荧光显微镜、激光扫描共聚焦显微镜、显微红外光谱（FTIR）和透射电镜（TEM）等技术，对其花粉萌发和花粉管生长过程进行了较为系统的研究，旨在进一步揭示裸子植物花粉管发育的调控机制。 本论文首先研究了外源Ca2+ 和3种调钙药物（A23187、EGTA、TMB8）对白皮松花粉萌发和花粉管生长的影响。结果表明，在离体培养条件下，高浓度的Ca2+（1%）能完全抑制白皮松花粉的萌发，低浓度的Ca2+ 则影响不大，而花粉萌发和花粉管生长的最适Ca2+ 浓度为0.01%。用Ca2+ 载体A23187、Ca2+ 螯合剂EGTA和钙通道阻滞剂TMB8分别处理花粉后，花粉萌发和花粉管生长均受到抑制。另外，用 Ca2+ 荧光探针 Fluo-3AM标记，对Ca2+ 的分布变化进行了观察，发现在花粉萌发的初期，Ca2+ 向萌发孔聚集。在正常生长的花粉管中Ca2+ 呈梯度分布，顶端荧光最强。与对照相比，A23187处理后花粉粒中荧光增强，而EGTA和TMB8处理的花粉粒中荧光强度均减弱。并且这3种调钙药物还破坏了花粉管顶端的Ca2+ 浓度梯度，最终导致花粉管的生长受阻。 花粉萌发和花粉管的生长依赖于RNA和蛋白质的不断合成。在放线菌素D的存在下，花粉萌发基本不受影响，但花粉管的生长速度下降，花粉管中RNA含量也减少。而经过放线菌酮处理后，花粉萌发和花粉管生长均受到抑制，花粉管中蛋白质含量降低，同时花粉管顶端显著膨大。通过SDS-PAGE的结果表明，花粉粒萌发前后蛋白质图谱有明显差异。FTIR光谱分析表明，两种抑制剂处理均导致花粉管壁的化学组成发生了变化，例如蛋白质和饱和酯含量减少，而羧酸的含量增加。此外，由放线菌酮和放线菌素D处理后，花粉管的超微结构也发生了明显变化，其中特别是花粉管顶端的分泌系统遭到严重破坏。 纤维素的正常合成对于白皮松花粉管的生长是必需的。在正常培养基中添加纤维素生物合成抑制剂2，6-二氯苯腈（DCB）后，花粉萌发几乎不受影响，但是花粉管的形态发生异常，生长速率降低。DCB处理还导致花粉管壁中纤维素含量下降，而胼胝质在花粉管顶端积累。用识别酯化果胶的JIM7和识别酸性果胶的JIM5对离体培养的白皮松花粉管进行标记后，发现果胶成分呈异常分布图式。FTIR光谱分析结果表明花粉管细胞壁中蛋白质、羧酸以及饱和酯含量增加。同时，在电镜下观察发现，花粉管细胞壁顶端呈现不均匀加厚，其中主要的细胞器，如高尔基体和线粒体等膜结构均遭到破坏。 上述结果说明，白皮松成熟花粉粒中已含有花粉萌发和花粉管早期生长所必需的Ca2+ 和RNA，但是在花粉管的后续伸长过程中仍需要外源Ca2+ 的参与以及新RNA、蛋白质的不断合成。与被子植物不同，裸子植物花粉萌发的启动也需要新蛋白的合成。尽管在花粉管中纤维素的含量很低，但是对于细胞壁的构建、花粉管的正常形态的维持起着关键作用。