加州鲈优势腐败菌的分离鉴定

为了研究加州鲈的优势腐败菌,采用16S r DNA基因测序手段进行腐败菌的分离鉴定。以感官评价、pH、总挥发性盐基氮(Total volatile base nitrogen,TVBN值)及产量因子(YTVBN/cfu)为指标,对菌种的致腐能力进行系统评估。鉴定结果表明,加州鲈肉样中共分离9种菌,分属普罗维登斯菌属(Providencia),哈夫尼菌属(Hafnia),气单胞菌属(Aeromonas),不动杆菌属(Acinetobacter),肠球菌属(Enterococcus),葡萄球菌属(Staphylococcus),希瓦氏菌属(Shewanella),和巨球菌属(Megasphaera)。其中,革兰氏阳性菌3种,革兰氏阴性菌6种。致腐能力实验结果显示,巴氏葡萄球菌(Staphylococcus pasteuri)样品从高品质终点到达感官拒绝点仅需1.5 h;培养24 h,样品pH最高可达7.35±0.33,TVBN最大可达160.02±0.28 mg/100 g,产量因子YTVBN/cfu可达227.32±1.08(10~(-9) mg TVBN/cfu),显著高于其他菌种样品(p0.05)。综上所述,巴氏葡萄球菌具有极强的致腐能力和蛋白质分解能力,是加州鲈鱼肉的优势腐败菌。     

Mercury in sport fish from the Sacramento-San Joaquin Delta region, California, USA

Total mercury (Hg) concentrations were determined in fillet tissue of sport fish captured in the Sacramento-San Joaquin River Delta and surrounding tributaries, a region particularly impacted by historic gold and mercury mining activity. In 1999 and 2000, mercury concentrations were measured in 767 samples from ten fish species. Largemouth bass (Micropterus salmoides), the primary target species, exhibited a median Hg concentration of 0.53 mug g(-1) (N=406). Only 23 largemouth bass (6%) were below a 0.12 mug g(-1) threshold corresponding to a 4 meals per month safe consumption limit. Most of the largemouth bass (222 fish, or 55% of the sample) were above a 0.47 mug g(-1) threshold corresponding to a 1 meal per month consumption limit. Striped bass (Morone saxatilis), channel catfish (Ictalurus punctatus), white catfish (Ameirus catus), and Sacramento pikeminnow (Ptychocheilus grandis) also had relatively high concentrations, with 31% or more of samples above 0.47 mug g(-1). Concentrations were lowest in redear (Lepomis microlophus) and bluegill (Lepomis macrochirus) sunfish, with most samples below 0.12 mug g(-1), suggesting that targeting these species for sport and subsistence fishing may reduce human dietary exposure to Hg in the region. An improved method of analysis of covariance was performed to evaluate spatial variation in Hg in largemouth bass captured in 2000, while accounting for variability in fish length. Using this approach, Hg concentrations were significantly elevated in the Feather River, northern Delta, lower Cosumnes River, and San Joaquin River regions. In spite of elevated Hg concentrations on all of its tributaries, the central Delta had concentrations that were low both in comparison to safe consumption guidelines and to other locations.     

鲈鱼肠道来源降胆固醇乳酸菌分离筛选及其益生功能评价

该研究探讨了从健康鲈鱼肠道中筛选分离出高效降胆固醇的乳酸菌,通过菌株鉴定、耐酸、耐胆盐、疏水性、自凝聚力和代谢物抑菌性评价的测定,评价并考察其体外益生作用。采用胆盐水解酶测定和体外降胆固醇试验,筛选分离得到一株高效降胆固醇的菌株ZG2YLu05,其胆盐水解酶（BSH）粗酶活和胆固醇去除率分别为0.82 µmol/(h?mL)和50.09%;在pH 3.0的培养条件下培养8 h,菌株的耐酸存活率为83.33%;在胆盐浓度0.3%的培养条件下培养8 h,菌株的耐胆盐存活率高达89.31%;在二甲苯中菌株的疏水性为46.82%,静置24 h后菌株的自凝聚力为92.93%,说明菌株具有良好的黏附潜力;菌株代谢物对大肠杆菌、金黄色葡萄球菌和沙门氏菌都有明显的抑制作用;经形态学观察和16S rDNA鉴定为戊糖乳杆菌（Lactiplantibacillus pentosus）。该菌株能够作为潜在降胆固醇乳酸菌用于开发辅助降脂益生菌制剂的生产。     

FISH RECRUITMENT IS INFLUENCED BY RIVER FLOWS AND FLOODPLAIN INUNDATION AT APALACHICOLA RIVER,FLORIDA

High human demand for limited water resources often results in water allocation trade‐offs between human needs and natural flow regimes. Therefore, knowledge of ecosystem function in response to varying streamflow conditions is necessary for informing water allocation decisions. Our objective was to evaluate relationships between river flow and fish recruitment and growth patterns at the Apalachicola River, Florida, a regulated river, during 2003–2010. To test relationships of fish recruitment and growth as responses to river discharge, we used linear regression of (i) empirical catch in fall, (ii) back‐calculated catch, via cohort‐specific catch curves, and (iii) mean total length in fall of age 0 largemouth bass Micropterus salmoides, redear sunfish Lepomis microlophus and spotted sucker Minytrema melanops against spring–summer discharge measures in Apalachicola River. Empirical catch rates in fall for all three species showed positive and significant relationships to river discharge that sustained floodplain inundation during spring–summer. Back‐calculated catch at age 0 for the same species showed positive relationships to discharge measures, but possibly because of low sample sizes (n = 4–6), these linear regressions were not statistically significant. Mean total length for age 0 largemouth bass in fall showed a positive and significant relationship to spring–summer discharge; however, size in fall for age 0 redear sunfish and spotted sucker showed no relation to spring–summer discharge. Our results showed clear linkages among river discharge, floodplain inundation and fish recruitment, and they have implications for water management and allocation in the Apalachicola River basin. Managed flow regimes that reduce the frequency and duration of floodplain inundation during spring–summer will likely reduce stream fish recruitment. Copyright © 2012 John Wiley & Sons, Ltd.     

Are smallmouth bass more mobile in large lakes than once thought?

Smallmouth bass Micropterus dolomieu are generally considered to be a sedentary species. Previous tagging studies in lentic systems have found low annual movements based on fishery-dependent tag returns or limited detections from electronic transmitters, though occasional long-distance movements have been observed (i.e., >30 km). In this study, we implanted 23 smallmouth bass sampled from a recreational tournament in Lake Erie with acoustic transmitters and monitored their movements for two years (September 2018–September 2020) using a large-scale array of passive acoustic receivers. We documented 42 percent (8/19) of the at-large fish making long-distance movements throughout Lake Erie; these fish moved an average distance of 109.9 ± 26.6 km (mean ± SE; ranging 3.5–355.1 km) per year. Importantly, six of eight fish crossed jurisdictional boundaries (five into Ontario waters and one into Michigan waters). One individual moved a total of 505.3 km over the two years, the furthest distance an individual smallmouth bass has been documented moving across the literature. While observed movements may have been initially biased due to tournament displacement and capture method, tagged fish continued to make long-distance movements in the second-year post-release. Previous movement studies may have underestimated smallmouth bass movement scope in large, lentic systems due to low spatial and temporal coverage of recapture effort (including receiver coverage) relative to system size. Our results suggest that some smallmouth bass can make consistent long-distance movements in large systems like the Laurentian Great Lakes, indicating this species’ spatial ecology remains understudied in large lentic systems.     

Post-tournament dispersal of smallmouth bass in western Lake Erie

Catch-and-release tournaments for smallmouth bass Micropterus dolomieu transport fish from many capture locations to a centralized release site. In the Great Lakes, these fish may be transported long distances (i.e., >100 km) and subsequently become concentrated at a release site, possibly negatively affecting subpopulations at popular fishing sites if fish remain concentrated in the area. To assess timing of post-tournament dispersal, 23 smallmouth bass were implanted with acoustic transmitters and released into Sandusky Bay (Lake Erie) after a large tournament (50 boats) in September 2018. Tagged fish were tracked via a grid of acoustic receivers. All surviving fish (n = 19) left the immediate vicinity of the release site (<500 m) after an average (±SE) of 13.2 (±2.4) d, with many (58%) returning to the main lake (19.7 d ± 3.4). Eight (42%) of the surviving fish left the release site but remained in the bay after 50 d. Based on the results from this study, long-term (>1 month) concentration of smallmouth bass at release sites is unlikely to be a problem for Lake Erie bass tournaments, but temporary (up to 1 month) accumulations of fish are possible. A fraction of tournament-released smallmouth bass resided in Sandusky Bay for extended periods (>2 months), which could be considered functionally harvested from main lake subpopulations. Currently, the frequency of bass tournaments on Lake Erie is uncertain, and better documentation of tournament frequency and scale is necessary to assess potential negative impacts on bass populations.     

模糊数学评价和主成分分析电子束辐照处理后的鲈鱼品质

电子加速器放射出的β射线对食品具有杀菌和保鲜的作用。为系统评价电子束辐照剂量对鲈鱼品质的影响,对鲈鱼进行8个梯度剂量(0.00、2.45、3.33、4.41、5.27、6.64、7.24、8.56 k Gy)的辐照,然后通过感官评价和模糊数学矩阵来计算感官评价综合隶属度,并采用Pearson相关系数和主成分载荷分析确定鱼肉质构的主要代表因素。模糊数学感官评价结果显示,剂量越大,感官评价隶属度等级越低;辐照2.45、3.33、4.41 k Gy时,鱼肉样品感官评价的综合隶属度较接近1级。质构测定结果及主成分分析表明,咀嚼度、弹性和胶着度是辐照后鱼肉的质构代表因素,其值随剂量变化有所波动;剂量低于4.41 k Gy时,对鱼肉质构的影响无统计学差异(P0.05)。综上所述,电子束辐照剂量低于4.41 k Gy时,能最大限度保持鲈鱼肉产品感官品质和质构特性。     

加州鲈腌制品仪器分析与感官评价相关性研究

目的研究鱼肉质构特性及其仪器测定和感官结果的相关性。方法选用不同腌制时间的加州鲈样品进行仪器质地剖面分析(texture profile analysis,TPA)和感官评价。结果主成分分析实验中,鲈鱼腌制品TPA指标和感官评价指标分别得出2个主成分,累计方差贡献率分别达87.39%和82.17%;腌制时间为2 h时,TPA指标值和感官评价较优。相关性分析结果表明,感官粘聚性与TPA咀嚼性、TPA胶黏性具有显著负相关性(P0.05,r=-0.713;P0.01,r=-0.834),感官胶黏性与TPA硬度显著正相关(P0.05,r=0.805)。结论选取感官指标为因变量,TPA指标为自变量进行逐步回归分析,得到具有统计学意义的感官粘聚性和胶黏性的预测方程,为鲈鱼腌制品在品质评价上的预测提供了依据。