Striped Bass eggs and larvae in the Miramichi River estuary: a resource pulse detectable only with molecular tools?

Ichthyoplankton surveys between 14 May and 15 July 1992 in the tidal fresh waters of the Northwest Miramichi River, New Brunswick, provide the first description of spawning by striped bass, Morone saxatilis, in any Gulf of St. Lawrence river. Surveys showed that striped bass spawned between late May and mid-June. Most eggs were produced in a single brief peak of abundance between 31 May and 2 June at daily average surface water temperatures of 15.6–16.6 °C. Spawning occurred largely within the first 12 km of tidal fresh water above the edge of the salt wedge. Peak spawning was centred along a 2-km stretch of river directly upriver of the salt wedge. Peak densities of larval stages were found near or upstream of the area of peak egg density. Larval densities were highest near the salt wedge.

The Striped Bass Morone saxatilis is an apex predator that supports recreational, commercial, and First Nations traditional fisheries in the Miramichi River, New Brunswick, Canada. Historic exploitation resulted in steep population declines, forcing a complete fisheries moratorium in 2000. After 13 years of recovery, a recreational fishery was reopened (May 2013) followed by a commercial fishery in 2018. These new opportunities for harvesting raised concerns about mercury levels in fish for human consumption as past levels have exceeded Health Canada guidelines of 0.5 mg/kg. We collected Striped Bass from the northwest Miramichi River in spring during the main recreational and commercial fishing seasons. Fish in the legal harvest slot for the recreational (50–65 cm TL) and commercial (50–80 cm TL) fisheries had total mercury in muscle tissue ranging from 0.08 to 0.43 mg/kg and from 0.08 to 0.63 mg/kg wet weight, respectively. Mercury levels in Striped Bass have decreased since the 1990s, but some individuals were close to or exceeded consumption guidelines. In addition, a preliminary angler creel survey revealed that only 8% of anglers retained their legal, three-fish limit (average harvest = 0.7 fish/angler/day). However, harvest of oversized fish was observed (11%), and a removal of ˜100,000 adults in the first month of the fishery by the recreational, commercial, and Indigenous fisheries is possible and represents a significant portion of the estimated adult population. We conclude that effective management of the Striped Bass fishery in the Miramichi River will require continued and more detailed angler surveys and population size and structure assessments accompanied by communication of current mercury levels in this species.

Physical disturbances and resource pulses are major structuring drivers of terrestrial and aquatic ecosystems. The accumulations of exported dead leaves from the Neptune grass, Posidonia oceanica (L.) Delile are ephemeral and highly dynamic detrital habitats offering food sources and shelter for vagile macrofauna community. These habitats are frequently subject to wind and storms which can add “new” detrital material to previous accumulations; these can be defined as resource pulses and could potentially impact the associated macrofauna. This study assesses the impact of an experimental resource pulse on the macrofauna associated with exported P. oceanica litter accumulations. The experimental design consisted of two pulse treatments (the addition of dead leaves with and without the associated fauna), and two controls (one procedural, and one total control), where the added material was left underwater for 14 days. Invertebrates then present in the sampled detritus were all identified and counted. Our data suggest that the responses of these invertebrates to resource pulses present intermediate characteristics between aquatic and terrestrial ecosystems responses. Inputting a moderate amount of dead P. oceanica leaves into experimental mesocosms had a non-negligible impact and rapidly affected the macrofauna community. Specialist detritivores species were boosted while herbivore/detritivore species dramatically decreased. Predators also showed a modest but significant density increase, demonstrating the fast propagation of the pulse response throughout the entire community and through several trophic levels. Strict hypoxia-tolerant species were also only observed in the treated mesocosms, indicating the strong influence of resource pulses on physico-chemical conditions occurring inside litter accumulations.

Acoustic telemetry was used to describe the behavior of individual striped bass Morone saxatilis and their use of the Miramichi River estuary during two consecutive spawning seasons in 2004 and 2005. In both years, prespawning striped bass staged in the lower and middle sections of the Miramichi River estuary downstream from the spawning area. Males and females moved in synchrony from the staging area to the spawning grounds in the Northwest Miramichi River. The dates of arrival at the spawning grounds were similar between sexes in both years, but significantly later (by about a week) in 2005. There were no significant differences in average daily water temperature on the dates of arrival at the spawning grounds for male and female striped bass, but water temperatures on the arrival dates were significantly cooler in 2005. Increases in temperature rather than the absolute temperature was the apparent cue initiating the movements of striped bass onto the spawning grounds. Females occupied the spawning grounds for 12 and 7 d in 2004 and 2005, respectively, significantly less than the approximately 15 d for males in each year. The shorter occupation of the spawning grounds by female striped bass was determined by their significantly earlier departure dates than males. Staging downstream of the spawning area by males and females, rapid ascent by both sexes to the spawning area, and the longer residency of male striped bass on the spawning grounds are important characteristics that must be considered when developing management actions to protect and rebuild the spawning stock of this northern population of striped bass.

Resource pulses affect productivity and dynamics in a diversity of ecosystems, including islands, forests, streams, and lakes. Terrestrial and aquatic systems differ in food web structure and biogeochemistry; thus they may also differ in their responses to resource pulses. However, there has been a limited attempt to compare responses across ecosystem types. Here, we identify similarities and differences in the causes and consequences of resource pulses in terrestrial and aquatic systems. We propose that different patterns of food web and ecosystem structure in terrestrial and aquatic systems lead to different responses to resource pulses. Two predictions emerge from a comparison of resource pulses in the literature: (1) the bottom-up effects of resource pulses should transmit through aquatic food webs faster because of differences in the growth rates, life history, and stoichiometry of organisms in aquatic vs. terrestrial systems, and (2) the impacts of resource pulses should also persist longer in terrestrial systems because of longer generation times, the long-lived nature of many terrestrial resource pulses, and reduced top-down effects of consumers in terrestrial systems compared to aquatic systems. To examine these predictions, we use a case study of a resource pulse that affects both terrestrial and aquatic systems: the synchronous emergence of periodical cicadas (Magicicada spp.) in eastern North American forests. In general, studies that have examined the effects of periodical cicadas on terrestrial and aquatic systems support the prediction that resource pulses transmit more rapidly in aquatic systems; however, support for the prediction that resource pulse effects persist longer in terrestrial systems is equivocal. We conclude that there is a need to elucidate the indirect effects and long-term implications of resource pulses in both terrestrial and aquatic ecosystems.

Toxicity of ozone-produced oxidants (OPO) to striped bass, Morone saxatilis, eggs, larvae, and fingerlings was determined under continuous-flow conditions. Eggs, tested in both fresh and estuarine water, were found to be significantly (P < 0.001) more sensitive to OPO in freshwater. The higher sensitivity found for striped bass eggs in freshwater suggests that ozone could have a more pronounced effect if discharged in freshwater industrial or municipal wastewaters located in the vicinity of a striped bass spawning area. The ozone data collected in this study were compared with previously published chlorine toxicity data for each striped bass life stage. The toxicity of chlorine and ozone was found to be similar with striped bass eggs and larvae in estuarine water. LC50's for fingerlings were 0.20 mg/L OPO at 6 h and 0.08 mg/L OPO at 96 h.Key words: ozone, oxidants, chlorine, striped bass, Morone saxatilis; wastewaters

The Kouchibouguac region, located in Atlantic Canada on New Brunswick's eastern coast was declared a provincial game refuge in 1969 and a National Park in 1979. Morone saxatilis (Striped Bass), a species of ecological and socio-economic importance, has long been considered a conservation priority within the park and the surrounding region. The creation of the National Park resulted in the closure of the region's commercial Striped Bass fishery and regulation of recreational fishery retention, turning the area into a key focal point for monitoring and conservation of Striped Bass within the southern Gulf of St. Lawrence. In the early 1990s, the Northwest Miramichi River was confirmed as a key spawning location for Striped Bass and the likely origin of all southern Gulf of St. Lawrence Striped Bass, a discovery which would remove the burden of local Striped Bass conservation and recovery from the park. Now, following a precipitous population decline, a 13-year fishing moratorium, and an unprecedented population recovery, Striped Bass have returned in great numbers to the southern Gulf of St. Lawrence. This review summarizes the history of the study of Striped Bass in Kouchibouguac National Park to prompt the continuation of research of Striped Bass under the climate of a presently recovered population. It remains possible that the recovered population could once again re-colonize spawning habitat within the rivers of Kouchibouguac National Park that may have been occupied historically.

The effect of acclimation temperature on the interactions of chlorine, ΔT and exposure duration to eggs, prolarvae and larvae of striped bass, Morone saxatilis

The upper Pettaquamscutt River Estuary contains a unique overwintering population of striped bass, Morone saxatilis (Walbaum). During the winters of 1974 and 1975, experimental gillnets were used to sample this population. Catch data was examined in relaiton to abundance and distribution. Length, weight, and sex of individuals were recorded and ovaries were examined. Ichthyoplankton samples taken in the area during May and June of 1974 were examined for evidence of successful striped bass spawning. A limited number of striped bass were gillnetted from the sample area. Nine were netted during 1974 and eleven during 1975. Ice limited sampling during the early winter. Gillnets were removed on April 15, and May 15 during 1974 and 1975 respectively. During both winters of sampling, bass were not taken from the sample area after the beginning of April, suggesting that they had left the area. Age class composition indicates the population was dominated by older fish. The possibility of gear selectivity is discussed. Females were more abundant than males. Measurement of ova diameters showed normal development when compared with those of southern spawning populations. No striped bass eggs or larvae were identified from ichthyoplankton samples. High salinities may limit the potential of this area as a natural spawning ground.

The future of biodiversity monitoring and conservation utilizing environmental DNA

PDF HTML阅读 XML下载 导出引用 引用提醒 养分资源脉冲供给对几种微藻种间竞争的影响 DOI: 10.5846/stxb201306281795 作者: 作者单位: 西南林业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 云南省教育厅科学研究基金理工类重点项目（2012Z069） The effect of resource pulse supply on interspecific competition of a few algal species Author: Affiliation: Southwest Forestry University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以淡水生态系统常见的5种微藻为研究对象，通过稳态条件下单一培养的方式获取各微藻在氮素或磷素缺乏条件下对应的生长特征参数和R*值，同时将5种微藻在养分资源脉冲供给的方式下进行混合培养，进而检测养分资源脉冲供给对几种微藻种间竞争的影响作用，并与基于稳态条件下所预测的微藻种间竞争结果进行比较。研究结果显示，在稳态条件下具有最小R*值的纤细角星鼓藻在与其它微藻的种间竞争过程中始终保持优势地位，而其余4种微藻在混合培养状态下的相对比重亦与其稳态条件下的R*值紧密相关。然而，资源脉冲供给条件下的竞争优势种纤细角星鼓藻能与其它种群数量较小的微藻共存。此外，在氮素和磷素的不同供给比例情况下，对应微藻群落的结构也会发生相应的变化。实验养分资源脉冲作用下多种微藻的共存现象与自然水体中的观测现象相一致，显示了资源脉冲可能是维持生物多样性水平的一个重要机制。 Abstract:Resource competition theory predicts that under equilibrium conditions, algal species with a minimal requirement for a specific limiting factor, or, in other words, algal species with the lowest R* value for that limiting factor would become the superior competitor and assert its dominance. In contrast, algal species with higher R* values would be out-competed by the superior competitor and thus undergo local extinction due to competitive exclusion. However, observations from natural aquatic ecosystems have repeated shown the fact that dominant algal species could coexist with algal species with small population size. Resource pulses of limiting nutrients might reduce competition intensity among algal species, and thus help solve this discrepancy between theoretical predictions and field observations. However, due to the existence of other confounding factors, such as regional species pool and spatial heterogeneity, our understanding of the effect of resource pulses on alleviating algal competition intensity and altering competitive outcome has been hindered. This study applied microcosms assembled with five algal species that are commonly found in natural freshwater ecosystem to test the effect of resource pulses on algal competitive outcome. Several growth parameters, including the half-saturation constant and the maximum specific growth rate, were determined using Monod model when individual algal species were grown as monocultures on a gradient of limiting nitrogen or phosphorous. Also, the R* value of each algal species was calculated to predict the competitive outcome when algal species were grown as polycultures under non-equilibrium conditions when limiting nutrient resources were supplied as fluctuation forms. To reduce confounding effect, spatial heterogeneity effect was reduced by shaking microcosms frequently, and regional species pool effect was minimized by assembling all microcosms with same algal species with equal abundance initially. Therefore, the non-equilibrium conditions in studied microcosms are directly caused by resource pulse supply, and the effect of resource pulses on algal competitive outcome could be strictly tested. Also, the observed results under non-equilibrium conditions could be compared with theoretical predictions based on equilibrium state assumption, and the validity of resource competition theory would be further assessed. The results showed that one green algal species, Staurastrum gracile, had the lowest R* value under either nitrogen- or phosphorous-limiting conditions. According to the resource competition theory under equilibrium settings, this algal species should be the superior competitor that would outcompete other algal species when grown together, ultimately resulting in the local extinction of other algal species due to competitive exclusion. In the present study, when resource pulses of limiting nutrients were supplied to simulate non-equilibrium conditions and when all five algal species were grown together, Staurastrum gracile remained the best competitor that was found in every microcosm with absolute dominance as predicted. However, this superior competitor coexisted with other algal species under resource pulse supply conditions. Clearly, resource pulses had lowered down algal competitive intensity and thus greatly reduced the possibility of competitive exclusion as long as resource pulse supply could persist. Additionally, for microcosms receiving different nitrogen to phosphorous ratios, corresponding community structure also varied in terms of species composition and identity. Our empirical result that multiple algal species could coexist with resource pulse supply is thus in line with many observational studies on natural aquatic ecosystem, indicating that resource pulse supply represents one of important mechanisms for the maintenance of biodiversity. 参考文献 相似文献 引证文献

The Chesapeake and Delaware Canal connects upper Chesapeake Bay with the Delaware River. The results of two years of intensive sampling effort in the C&D Canal suggest that this area may be one of the more important spawning grounds of striped bass, Morone saxatilis (Walbaum), in the Chesapeake Bay region. Concentrations of striped bass eggs found during the period of peak spawning may be the highest that have been reported. Limited evidence suggests that the C&D Canal has provided a favorable alternative to now destroyed historical spawning grounds of striped bass in the lower Susquehanna River.

From water to land: How an invasive clam may function as a resource pulse to terrestrial invertebrates

Declines of American shad (Alosa sapidissima) populations in the Chesapeake Bay have led to fishing moratoria in Virginia and Maryland. Overfishing, blockage of spawning runs, degradation of water quality, and habitat destruction are postulated causes of population decreases. While moratoria and efforts to restore the fishery continue, it is imperative to garner information regarding quality and quantity of spawning habitat. Management efforts then may be focused on particular reaches of rivers, thus targeting areas for impediment removal, water quality improvement, and habitat protection. American shad eggs and larvae were collected in 1997-1999 as evidence of spawning habitat use. The areas of study were the Mattaponi and Pamunkey rivers, two unimpeded tributaries of Chesapeake Bay, where shad populations are low compared to historic levels, but currently at the highest level of any Virginia stock. Information from initial ichthyoplankton sampling during spring 1997 was used to modify sampling locations and techniques for the second and third year of sampling. Striped bass (Morone saxatilis) is thought to use similar river reaches as American shad during spawning, and interactions of these species may affect spawning or survival of progeny. Distribution and relative abundance of eggs and larvae of American shad and striped bass were compared between rivers. Temporal overlap in spawning by the two species occurred throughout the sampled period in both rivers. American shad eggs and larvae were more abundant on the Mattaponi River than the Pamunkey River by a factor of 5.5 and 4.6, respectively. Striped bass eggs and larvae were more abundant on the Pamunkey River than the Mattaponi River by a factor of 29 and 9.9, respectively. There was overlap between the extreme ranges of spawning for shad and striped bass, but the primary spawning habitat of each species was spatially disjunct in both rivers.

Modeling the Effects of Potential Salinity Shifts on the Recovery of Striped Bass in the Savannah River Estuary, Georgia–South Carolina, United States