Long‐term changes in fishery resources of an estuary in southwestern Atlantic according to local ecological knowledge

Long‐term changes in the abundance of fisheries resources from the Patos Lagoon estuary and adjacent coastal waters in southern Brazil have been observed. Despite this understanding, it is well known that the perception of pristine state of the environment is susceptible to inter‐generational changes, commonly known as shifting baseline syndrome (SBS). An useful approach in the reconstruction of pristine scenarios and in lack of data, as often occurs in small‐scale fisheries, is the local ecological knowledge (LEK). Temporal changes in the perception of 81 fishers with 1–63 years of fishing about the resources status were analysed. More experienced fishers reported larger catches, heavier individuals and perceived a greater number of species as "scarce" nowadays and "common" at the beginning of their careers proving the existence of a SBS among them. Over time, the number of fishing sites with very high catches decreased and fishing sites shifted from the lower towards the upper estuary. The perception of the fishers corroborated the real decreasing scenario in estuarine fisheries resources shared with industrial fishing in coastal waters. The results reinforce the utility of LEK for reconstruction of biological scenarios when no empirically obtained data are available.     

Gill net selectivity for perch (Perca fluviatilis) in the Szczecin Lagoon, Poland

This paper presents the scientific basis for changes in the minimum mesh size in gill nets, from 28 to 30 mm, introduced by fishery management in Poland to limit the catch of undersized perch (those less than 17 cm total length). Experimental fishing with six different mesh sizes was performed in accordance with commercial fisheries practice. A bi-normal selection curve was fitted to the data by including the between-set variation in the model. The locations of the primary and secondary modes of the bi-normal curve on the transformed length scale (length/mesh) were estimated to be 6.95 and 7.41, respectively. The results indicated that a minimum mesh size in gill nets of 28 mm should be sufficient to ensure a low level of discards as well as protecting the interests of fishermen.     

Clam farming quality as a management tool: A proposal based on recent studies in Northern Adriatic lagoons

The rapid and extensive spread of the clam Tapes philippinarum in Northern Adriatic lagoons, mostly in the lagoon of Venice (550 kmq), has led to severe exploitation by mainly free fishing, thus breaching the law. To contrast this unsustainable overexploitation, to which the present decreasing clam harvests are at least partly due, the local fishing authority has recently prepared a Master Fishing Plan for clam production, which is at present under way: the free fishing system must be replaced by a licencing system aimed at regulating market supply and mainly at converting more than 1000 fishermen into clam farmers. Moreover, a number of regulations for both vessels and harvesting techniques and management rules, such as daily clam harvests and fishing times, have been established. Although these newly introduced regulations may be regarded as valuable tools for preserving both the lagoon environment and the resource itself, they do not adequately consider protection for consumers. Although the licensed water areas have been evaluated as safe according to Italian law, at present no guarantees certify the quality of the clams harvested from them, due to the fact that the lagoon of Venice has polluted areas from which clams may be collected illegally and recycled to the legal market simply by putting them into the approved licensed areas before harvesting and marketing them. This paper therefore proposes a number of measures to be undertaken within the framework of good farming practices. The aim is to improve product quality by certification procedures in all production phases, and to guarantee the definite origin of farmed clams.     

水生植物对水体污染物的清除及其应用

针对水体污染程度的不同,利用水生植物对氮、磷、重金属及有毒有机物等各类污染物的清除作用,通过水生植物在污染治理中的应用实践,并与其他方法进行分析比较,说明了水生植物净化法具有独特优点。指出了该方法使用的可行性,并对其在污水处理方面提出了相应的展望和建议。     

Long‐term records (1781–2013) of European eel (Anguilla anguilla L.) production in the Comacchio Lagoon (Italy): evaluation of local and global factors as causes of the population collapse

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Hydrodynamic modeling and management alternatives in a Mediterranean, fishery exploited, coastal lagoon

Model development is described, related to the restoration efforts of Vassova Lagoon, a small and shallow, fishery exploited coastal lagoon, located in the region of eastern Macedonia, N. Greece. This lagoon has been configured and is used for fisheries, by having dredged through tidal channels and installed fish entrapment devices. Decreases in fish production have been related to poor seawater circulation, limited water renewal and related water quality problems. The aim of this study is to evaluate the current situation of the lagoon and propose alternative management scenarios for improvement of water flow and lagoon ecosystem. The SWMM-EXTRAN mathematical model has been adapted, calibrated, verified, and applied to describe the current situation of the lagoon, and evaluate alternative scenarios for increasing tidal flushing and water residence time. Data necessary for model validation have been collected in the field. Among the tested restoration alternatives were the following: widening and/or deepening the lagoon inlet; constructing a second inlet; widening and/or deepening the tidal channels inside the lagoon. The combined influence of opening the existing communication channel of Vassova Lagoon with the adjacent Eratino Lagoon was also considered for each scenario. The implications of the various scenarios on lagoon's fisheries management are discussed. The alternative of constructing a second tidal inlet channel, 5 m wide, and keeping the Eratino Lagoon channel open provided most tidal flushing and increased internal and inlet flow that favors recruitment of juvenile fish. This alternative was proposed for implementation.     

天鹅湖潟湖表层沉积物磷的吸附容量及潜在释磷风险

研究了天鹅湖潟湖表层沉积物对磷的吸附容量,分析了沉积物磷吸附指数(PSI)、磷吸附饱和度(DPS)及由这两个指标构成的磷释放风险指数(ERI),预测了不同区域沉积物磷的潜在释放风险。结果表明,沉积物的PSI变化范围为7.44~28.53 mg L/100 gμmol,湖北部和中部沉积物的PSI值较高;DPS与PSI的变化趋势相反,变幅为0.85%~4.99%,表现为湖南部和中部沉积物的DPS高于北部。沉积物的PSI与磷的理论吸附容量(Qmax)呈极显著正相关(P0.01),而DPS与沉积物各理化参数间的相关性较差。有机质(OM)、活性铝(Alox)和粘粒是表层沉积物对磷持留的主要影响因素。此外,天鹅湖潟湖表层沉积物的ERI变化范围为2.93%~44.70%,磷释放诱发富营养化的风险处于中度范围,其中东南部发生富营养化的风险较高     

New data on the ecology of kutum, Rutilus frisii (Nordmann, 1840) from the Caspian Sea

Abstract– In the anadromous cyprinid kutum, Rutilus frisii (Nordmann, 1840) from the Anzali Lagoon, Iran, the following hitherto unrecorded characters were found. The complex life-style of juvenile kutum is reflected directly in their body size and preferred habitat, and indirectly in their growth rate and the formation of scale annuli. The early juveniles did not move downstream to the feeding grounds in the sea as they are supposed to do in populations inhabiting the Caucasian coast of the Caspian sea, but most of them spend one or two years in fresh or brackish water. Moreover, most kutum scales carried one or two juvenile marks. It appears that the time spent in fresh water is inversely proportional to the age of the kutum. On average about 43% of fish 2 years old and older, spent their first year in fresh or brackish water, while 57% spent two years there. The rate of growth in length is substantially different in both groups. Fish that enter the sea in their second year of life grew faster but their life span seems to be shorter than those which spent two years in fresh or brackish water.     

筼筜湖浮游植物的分布与生态评价

根据2001～2002年对筼笃湖所采集样品的分析,对浮游植物的种类组成、优势种组成和细胞数量等的空间分布和季节变化进行分析研究.结果表明,筼筜湖浮游植物共出现91种,优势种为中肋骨条藻(Skeletonema costatum)和裸藻(Euglena),浮游植物具有种类数少,细胞数量高,丰富度、多样性指数和均匀度都较低,优势度高的特点,表明筼筜湖水体受污染的程度较为严重.     

Assessing redesigned effectiveness of the water quality monitoring program in the Indian River Lagoon,Florida

• 1. In 1996, the long‐term water quality monitoring network (WQMN) program in the Indian River Lagoon (IRL) of the St. Johns River Water Management District (SJRWMD) that began in 1988 was redesigned to eliminate statistically redundant sampling and satisfy modeling requirements.
• 2. Methods, procedures, and equipment were standardized across multi‐agency monitoring partners to produce reliable and comparable data. The redesigned strategy also included elements to determine previously unknown quantities such as differences in water quality parameters with depth and tidal cycle.
• 3. Reduction of sampling sites from 150 to 24 resulted in a significant improvement of standard deviation (t‐test; α = 0.05) for most water quality parameters analysed. The enhancement in data quality has demonstrated a more cost‐effective and efficient monitoring tool to measure the water quality of the seagrass environment in the IRL.
• 4. Results supported the view of a well‐mixed condition at the sampling stations on most days. Refocusing and streamlining the water quality monitoring program within the context of its mission would enable conversion of data into meaningful information regarding the interrelationship among water quality, photosynthetically active radiation (PAR), and seagrass PAR requirements.

Copyright © 2003 John Wiley & Sons, Ltd.