Perch Production Research Articles

Downscaled climate change threats to United States freshwater finfish aquaculture

Climate change threatens food production, yet gaps remain in our understanding of these threats to aquaculture, the fastest growing food production subsector. To build climate-resilient practices and policies we need to quantify and map current and future climate threats to aquaculture. Here, we explore how downscaled climate change [SSP 2 (eq. RCP 4.5) and SSP 5 (eq. RCP8.5), CMIP6] threats – including water scarcity, flooding, and increasing temperature – may directly affect United States (US) freshwater farmed fish (N = 7) based on their biological thermal tolerances and indirectly challenge the operations required for production, including to the human workforce. Aquaculture in the US is dominated by catfish, trout, and tilapia production and is widespread, with some form of finfish aquaculture present in every state and nearly half of all counties across the country. Given the current location of catfish, tilapia, bass, and carp in the US and their tolerance to warmer conditions, we find increasing temperatures are less likely to biologically impact these species negatively. In contrast, current trout, sturgeon, and perch production will be biologically threatened by rising temperatures. With respect to operational needs for facilities, increases in ‘wet bulb’ temperatures in the Southeast will regularly challenge human physiological limits and constrain worker capacity. Drought in the Southwest will also limit an intrinsically water dependent system, affecting nearly all taxa. While current areas of aquaculture will tend to become increasingly challenging for farmed fishes, new potential habitats will open up for nearly all species. Overall, in the absence of immediate greenhouse gas mitigation, there are several non-mutually exclusive climate adaptations, yet these adaptations can be extremely costly. Ultimately, freshwater aquaculture in the US is going to be under intense climate pressure, which may drive out small operations and cause the country to further increase dependence on international aquatic food imports.

Optimizing Eurasian Perch Production: Innovative Aquaculture in Earthen Ponds Using RAS and RAMPS-Economic Perspective.

Aquaculture in rural areas, carried out in accordance with current EU requirements, aims to contribute significantly to the conservation of the biodiversity of aquatic resources, the protection of which is a prerequisite for sustainable economic and social development. The objective of this study was to present the conceptual and technical framework and to analyze the costs and profitability of producing the consumer-attractive Eurasian perch (Perca fluviatilis L.) based on the untapped potential of hatchery infrastructure and dedicated earthen ponds for common carp (Cyprinus carpio L.) production. The experiments were conducted under Polish conditions, but the results/methods can be successfully applied in other countries, mainly in Central and Eastern Europe, where production in earthen ponds is the basis of aquaculture production. The analysis of the profitability of the venture shows that the cost structure was dominated by labor and feed inputs. Despite high variable costs, this type of production can be profitable and contribute to food security and economic development in line with the EU's Blue Growth Strategy. The article also analyzes the potential opportunities and risks of fish production based on the Recirculating Aquaculture System (RAS) and the Recirculating Aquaculture Multitrophic Pond System (RAMPS).

System design and production practices of aquaponic stakeholders.

Aquaponics is an agricultural practice incorporating aquaculture and hydroponic principles. This study assesses the current system design and production practices of the aquaponic industry, compares these metrics by stakeholder group, identifies trends, and provides recommendations for future development. An electronic survey of aquaponic stakeholders was conducted from December 2019 to June 2020 targeting hobbyists, producers, and educators from various aquaponic-focused professional associations, email and social media groups. Of 378 total responses, 84% came from the United States and were clustered in plant hardiness zones five to nine. Aquaponic systems were commonly homemade/do-it-yourself (DIY), many of which incorporated commercially available (turn-key) technology. Most growers used coupled systems that integrated recirculating aquaculture systems and either deep-water culture (DWC) or media bed hydroponic units. Common plant lighting sources were sunlight and light emitting diode (LED). Water sources were typically municipal or wells. Personal labor input was typically less than 20 hrs/wk. Funding sources were primarily personal funds, followed by government grants, and private investor funds. System sizes varied greatly, but the median area was 50 to 500 ft2 for hobbyists and educators and 500 to 3,000 ft2 for producers. Respondents commonly sold vegetable produce, training and education, food fish, and microgreens. Tilapia and ornamental fish were commonly grown, with 16 other species reported. Common crops were lettuce, leafy greens, basil, tomatoes, peppers, and herbs with many additional lesser-grown crops reported, including cannabis. Overall, the industry still growing, with a large portion of stakeholders having less than two years of experience. However, veteran growers have remained in operation, particularly in the producer and educator groups. The survey results suggest a shift away from outdoor systems, media beds, tomatoes, ornamental fish, and perch production, and a shift toward decoupled systems, DWC, drip irrigation, and wicking beds, larger system area, leafy greens, and trout/salmon production compared to previous industry surveys. The reduced diversity of plant species grown suggest some level of crop standardization. Commercial producers tended to sell more types of products than other stakeholders, suggesting that diversification of offerings may be key to profitability. The combined production area specified by respondents indicates the industry has grown substantially in recent years. Finally, the presence of bank loan-funded operations suggests increased knowledge and comfort with aquaponics among lenders.

The dilemma of opportunity in developing a life cycle assessment of emerging aquaculture systems - a case study of a Eurasian perch (Perca fluviatilis) hatchery recirculating aquaculture system.

Eurasian perch (Perca fluviatilis) has been identified as an aquaculture species that can contribute to supply and supplement wild stocks for niche markets in European alpine regions. As a species earmarked for expansion it is important to benchmark the environmental impact associated with its production. The case study site presented a dilemma of opportunity (the dilemma of carrying out a study to inform production processes, at the beginning or development of a product/system or to wait until it is established and in steady state). This dilemma is often a limiting factor in the assessment of emerging systems or products and as a result this site was data deficient in a number of areas (energy use, growth rate and water use) which required the use of an ab initio approach to overcome these gaps. Data for growth, oxygen and heating were modelled for one kilogram of fish to the farmgate for 2018. The generated data was investigated for environmental impact using life cycle assessment (LCA). Impact categories included in the study were global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), freshwater and marine ecotoxicity potential (FAETP and MAETP), cumulative energy demand (CED), net primary production use (NPPU) and water use. The results indicated that there was high variability between the inputs, outputs and impacts associated with the production of perch to the farmgate. The highest variability was observed in live feed use and energy inputs between the batches. This was related to egg quality and the survival rates of the batches. The nursery stage of production was found to have the greatest environmental burden of all stages. EP was dominated by emissions from the stock. Electricity use and feed were the greatest contributors to GWP, AP and FAETP. Electricity and heating had the greatest share of CED and MAETP. Water use (using the AWARE methodology) was dominated by feed production, fish culture and electricity generation. The result of this analysis echoes that of similar studies in that the dominant contributors to the life cycle impacts of RAS products are electricity and feed. This study constitutes the first LCA of perch production in RAS. In addition to this, the study also outlines a framework and methodology, which can be used to overcome the dilemma of opportunity when assessing the environmental burden of an emerging aquaculture system or species. This approach allows operators to overcome data deficits, which may exist and implement impact strategies prior to the finalisation of the process or system.

Stable isotopes and morphology reveal spatial and annual patterns in trophic reliance of an invertivorous juvenile fish

AbstractEcological studies have traditionally treated fish species or populations as homogenous groups; however, numerous studies have shown that intrapopulation variation in resource use is widespread. Within‐species diet differences are evident in small and large freshwater systems and may influence trophic and population dynamics. In a previous study of young yellow perch, spatial intrapopulation diet variation was observed for stomach contents, a relatively short‐term diet indicator. In the current study, we build upon the earlier study of yellow perch in Saginaw Bay, Lake Huron, and assess patterns of long‐term diet indicators (stable isotopes and morphology) to assess consistency of diet variation over time and improve characterisation of trophic differences among sites. Specifically, we analysed soft tissue samples for carbon (δ13C) and nitrogen (δ15N) isotope ratios and used geometric morphometrics to describe morphological variation of young yellow perch. While both isotopes displayed significant spatial differences, δ15N values demonstrated a much clearer separation among sites, with greater δ15N values for yellow perch collected closer to the mouth of the Saginaw River. Morphological variation also was more apparent among sites rather than between years or months, with more streamlined yellow perch morphologies evident at sites where they consumed high proportions of zooplankton relative to benthic invertebrates. Somewhat unexpectedly, soft tissue δ13C values varied strongly between the two study years; however, the ultimate cause of such interannual variation in δ13C is unclear. These long‐term indicators showed consistent spatial differences, which suggests that individual fish are using resources at a particular site long enough to reflect a stable isotope or morphological signal. Yellow perch production at different locations seemingly relies on different prey resources, suggesting that annual variation in dominant trophic pathways may alter the performance of yellow perch at each location.

Экономическая эффективность формирования ремонтно-маточного стада судака на рыбоводных хозяйствах Казахстана

The article highlights the problem of the industrial press on the pike perch population in all reservoirs of Kazakhstan and the sharp decline in its population due to increased exports of pike perch to Europe, which led to the need to fill the shortage of fish stock by forming pike perch broodstocks in the fish farms and increasing the importance of aquaculture. There are presented the results of introducing the technology of pike perch broodstocks formation in conditions of the fish farm HalykBalyk, LLP, which is carried out in two ways: by a method of domestication that provides catching pike perches from the natural reservoirs and adopting the spawners to the con-ditions of the fish farm: by obtaining offspring from the wild pike perch producers and growing the seeding material in ponds with subsequent selection for the broodstock. There have been given the calculations and analysis of the economic efficiency of biotechnological techniques for the phased formation of the breeding stock of pikeperch in a fish farm. There are presented the data on the cost of domestication of pike perch producers harvested in the natural pond and transported from the fishing sites to the hatcheries, as well as fish products: fertilized eggs, larvae that switched to mixed feeding, raised juveniles, fingerlings and two-year-olds raised in polyculture with traditional fish species in ponds in order to form a breeding stock of pike perch by the ‘ab ovo’ method. A diagram of the production processes of forming pike perch broodstock is presented. To determine the economic efficiency of growing pike perch yearlings and two-year-olds in the ponds in polyculture with carp and grass carp, the general costing of ponds, specific production costs and data on fish catch in monetary terms are presented. A comparative analysis of the results has been held; the ways to reduce the cost of pike perch production at each stage have been indicated.

Genetic characterization and relatedness of wild and farmed Eurasian perch (Perca fluviatilis): Possible implications for aquaculture practices

Aquaculture of the Eurasian perch, Perca fluviatilis, in recirculating systems has emerged over the past decades to become a significant way of diversification for inland areas in Europe. The development of such a production relies partly on the improvement of growth performance (i.e., reducing production costs), which requires suitable genetic management of broodstocks and the development of selective breeding programs. In this context, the present study was undertaken assessing for the first time the genetic diversity of farmed stocks of perch. Twelve microsatellite loci were used to investigate the genetic diversity of nine farmed stocks (547 individuals) from two perch farms located in France and their supposedly wild founder population from Lake Geneva (394 individuals). First, the wild population displayed the lowest genetic diversity and differed genetically from all farmed populations except one, XB2. Second, genetic diversity did not decrease between farmed breeders and their potential offspring. However, in the three groups of broodstock-offspring the number of alleles decreased by 10%, 21%, and 15%, respectively. In addition, effective population size decreased in all offspring groups. A family structuring was also observed among broodstocks and their offspring, with an unequal family contribution being suspected. In the absence of parental information, these results attest to the utility of genetic tools to evaluate genetic diversity and the necessity of a monitoring program to maintain genetic variability among farmed perch. Genetic variability among farmed stocks appears to be sufficient for perch production to be sustainable and selective breeding programs to be developed.

Influence of Smallmouth Bass Predation on Recruitment of Age‐0 Yellow Perch in South Dakota Glacial Lakes

AbstractWe estimated the influence of predation by Smallmouth Bass Micropterus dolomieu on recruitment of age‐0 Yellow Perch Perca flavescens in two northeastern South Dakota glacial lakes. We estimated a likely range in consumption of age‐0 Yellow Perch using Smallmouth Bass diet information from two time periods when age‐0 Yellow Perch constituted high (2008) and low (2012 and 2013) proportions of Smallmouth Bass diets, and bass population size estimates as inputs in a bioenergetics model. The proportion of age‐0 Yellow Perch consumed by the Smallmouth Bass populations was determined by comparing estimates of consumption with estimates of age‐0 perch production. During 2008, age‐0 Yellow Perch constituted between 0% and 42% of Smallmouth Bass diets by weight, whereas during 2012 and 2013, age‐0 perch constituted between 0% and 20% of bass diets by weight. Across both lakes and time periods, production of age‐0 Yellow Perch ranged from 0.32 to 1.78 kg·ha−1·week−1. Estimates of Smallmouth Bass consumption measured during the same intervals ranged from 0.06 to 0.33 kg·ha−1·week−1, equating to consumption of between 1% and 34% of the available Yellow Perch biomass. Given current conditions relative to Smallmouth Bass abundance and consumption dynamics and production of age‐0 Yellow Perch, it does not appear that Smallmouth Bass predation acts as a singular factor limiting recruitment of age‐0 Yellow Perch in our study lakes. However, future research and management initiatives should recognize that the long‐term impact of Smallmouth Bass predation is not static and will likely fluctuate depending on environmental (e.g., temperature) and biotic (e.g., trends in macrophyte abundance, predator and prey population structure and abundance, and predatory fish assemblage dynamics) characteristics.Received December 19, 2014; accepted April 20, 2015

The “self cleaning inherent gas denitrification-reactor” for nitrate elimination in RAS for pike perch (Sander lucioperca) production

Denitrification reactors have proven their functionality in commercial recirculation aquaculture systems (RAS). Nevertheless, clogging occurs due to the low hydraulic loads necessary to accomplish anoxic conditions for a successful denitrification process in RAS, which hampers the adjustment of stable working conditions within fixed bed denitrification reactors. Reactors working on the basis of activated sludge demand careful hydraulic control and/or complex configurations for sludge retention.To develop a low-maintenance denitrification reactor, an enclosed moving bed filter, driven by recirculation of the inherent, oxygen poor gas was designed. A Self cleaning Inherent gas Denitrification reactor (SID-reactor) of 0.65m3, which offered a moving bed volume of 0.39 m3 was connected with a RAS of semi-industrial scale for pike perch (Sander lucioperca) production. This species indicates suboptimal environmental conditions (as e.g. NO3-N concentrations above approximately 68mgl−1) by prompt reduction of the feed intake. In different experimental series, the SID-reactor was operated with denatured ethanol, methanol, acetic acid or glycerin as carbon sources and changing operational modes.Clogging was prevented by a 40 second inherent gas recirculation twice an hour, which provided continuous, maintenance free operation with marginal energy demand. With inlet (RAS) and outlet NO3-N concentrations in the range of 49mgl−1 and 12mgl−1, mean denitrification rates of 199g to 235g NO3-N per m3 moving bed volume and day were determined for all tested carbon sources. Negative effects on the feed intake of the reared pike perch were detected with all carbon sources except methanol. Changing the mode of operation to continuous circulation of the filter bed at inlet NO3-N concentrations of 26mgl−1, the denitrification performance reached 451g NO3-N per m3 moving bed volume and day. The SID-reactor allowed for the reduction of freshwater exchange in the pike perch RAS from 600 l to 70 l (−88%) and the sodium bicarbonate buffer from 182g to 31g (−83%) per kg of administered food. The easy and reliable operation of the SID-reactor could help to establish controlled denitrification as a routine purification step in RAS.

Twin-screw Extrusion Processing of Vegetable-based Protein Feeds for Yellow Perch (Perca flavescens) Containing Distillers Dried Grains, Soy Protein Concentrate, and Fermented High Protein Soybean Meal

<span style="color: #800000; font-family: Times New Roman; font-size: small;"> </span><p class="MsoNormal" style="margin: 0in 0in 4pt; line-height: 12pt; mso-line-height-rule: exactly;">Changing to alternative protein sources supports production of more economic aquafeeds. Two isocaloric (3.06 kcal/g) and isonitrogenous (40% db) experimental feeds for juvenile yellow perch were formulated with incorporation of fermented soybean meal (FSBM) and soy protein concentrate (SPC), each of which were at two levels (0 and 20% db), along with constant amounts of high protein distillers dried grains (DDG) (~30% db), and appropriate amounts of other ingredients. Using a pilot scale twin-screw extruder, feed production was performed in two replications for each diet at conditioner steam levels of 0.11 to 0.16 kg/min, extruder water of 0.11 to 0.19 kg/min, and screw speeds of 230 to 300 rpm. The effects of SPC and FSBM<ins datetime="2012-07-09T13:59" cite="mailto:k"> </ins>inclusion on extrudate physical properties were compared with those of a control diet (which contained 20% fishmeal and ~30% DDG). Inclusion of 20% FSBM and 20%SPC resulted in a substantial decrease in unit density by 9.2 and 24%, but an increase in lightness, greenness, yellowness, and expansion ratio of the extrudates by 7, 27, 14, 7, 17, 34, 15, and 16.5%, respectively. SPC inclusion led to a considerable increase in water absorption, thermal resistivity, and thermal diffusivity by 17.5, 6.3, and 17.6%, respectively, whereas no significant change was observed for these properties with incorporation of 20% FSBM. Additionally, all extruded products had high durability. Taken together, using ~30% DDG with20% FSBM or20% SPC as alternative protein sources resulted in viable extrudates with properties appropriate for yellow perch production. A future study investigating the effect of extrusion processing conditions on the production of complete vegetable-based protein feeds for yellow perch species would be appropriate.</p><span style="color: #800000; font-family: Times New Roman; font-size: small;"> </span>

A new classification of a preovulatory oocyte maturation stage suitable for the synchronization of ovulation in controlled reproduction of Eurasian perch, Perca fluviatilis L

To improve controlled reproduction of Eurasian perch Perca fluviatilis, the criteria for the evaluation of final oocyte maturation stages were revised. The new classification covers six preovulatory maturational stages (I -VI) from the end of vitellogenesis to germinal vesicle breakdown (GVBD) and was based on macroscopic changes of preovulatory oocytes (position of the germinal vesicle, GVBD, oil droplets coalescence). The observation was performed during out-of-season artificial reproduction with the use of a single hCG injection (500 IU/kg). The classification was subsequently verified with the controlled reproduction of wild female perch with the use of hormonal stimulation (500 IU hCG/kg of body weight at 12°C). The females were at different maturational stages and constituted respective experimental groups (I-VI). During the experiment, ovulation appeared to be considerably synchronized within particular groups. Statistical differences in latency time (time between hormonal treatment and ovulation) were found between experimental groups (mean latency time: 110, 92, 68, 49, 29 and 18 h in groups representing VI, V, IV, III, II and I stage of the proposed classification, respectively). The proposed classification and the results presented in the study allowed for effective synchronisation of ovulation. The use of our new oocyte maturation classification may positively influence the effectiveness of Eurasian perch production.

Perch production in forest lakes: the contribution of abiotic and biotic factors

Horppila J, Olin M, Vinni M, Estlander S, Nurminen L, Rask M, Ruuhijärvi J, Lehtonen H. Perch production in forest lakes: the contribution of abiotic and biotic factors. Ecology of Freshwater Fish 2010: 19: 257–266. © 2010 John Wiley & Sons A/SAbstract – The biomass, growth and production of perch (Perca fluviatilis (L.)) in five humic forest lakes in southern Finland were estimated and the abiotic and biotic factors contributing to the between‐lake differences were explored. The average perch biomass in the study lakes varied from 13.1 to 45.6 kg·ha−1 and annual production from 6.0 to 16.5 kg·ha−1. The highest biomass and production were found in Lake Majajärvi with highest water colour and nutrient concentration. Variability in fish density rather than in individual growth rate seemed to be the main factor behind the between‐lake differences in perch production. No dependence of perch production on water transparency was found, because transparency had a stronger effect on individual growth than on fish density. The length increment of perch in their second year increased significantly with water transparency but at older ages no such dependence was found. At age of 4 years, the growth rate of perch decreased with perch density, indicating intraspecific competition for benthic food resources. At age of 7 years, the growth rate increased with increasing roach (Rutilus rutilus (L.)) abundance, suggesting that roach served as a resource for piscivorous perch. The effects of predatory top‐down control on perch populations were probably obscured due to the variable size and water quality of the study lakes.

Heterosis in fingerlings from a diallel cross between two wild strains of silver perch (Bidyanus bidyanus)

Cross-breeding was investigated as a strategy to improve performance of the Australian native freshwater fish, silver perch (Bidyanus bidyanus Mitchell) through the exploitation of heterosis during the fingerling phase of production. Growth, and mid and best parent heterosis of two wild strains, Cataract Dam (C< C,) and Murray River (M< M,) and their reciprocal crosses (C< M, and M< C,) were evaluated in cages and ponds through summer, and in tanks in a re-circulating aquaculture system during winter. The M C cross grew significantly faster than the reciprocal cross and pure strains in cages and tanks, had the lowest coefficients of variation of weight and length and was 20.9% and 16.0% heavier than midparent and best-parent average, respectively, when grown in ponds. Differences in growth between the reciprocal crosses were also evident, with C M expressing significantly less heterosis in cages and tanks. Faster growth of M C was attributed to greater appetite; however, at sizes approaching 250 g this feeding vigour diminished. The results of this study suggest that use of the M C cross has the potential to reduce the length of the culture period and lower costs of silver perch production.

Salinity tolerance of cultured Eurasian perch, Perca fluviatilis L.: Effects on growth and on survival as a function of temperature

Eurasian perch is generally only considered to be a candidate for freshwater aquaculture even though wild populations are found in estuarine and brackish water habitats. Little knowledge exists on two issues a) the effect of temperature on the salinity tolerance of perch and b) the long-term effects of brackish water on their overall growth performance. The present study addresses these two questions. Firstly, the effect of temperature (12, 15, 20 and 25°C) on perch survival of a salinity challenge at either 13 or 18‰ was determined. Survival was unaffected by 13‰ at the two lowest temperatures whereas higher temperature and higher salinities had a dramatic detrimental effect (at 25°C, 50% mortality was reach at 62h and 39h for 13‰ and 18‰, respectively). Secondly, we examined the effect of salinity on growth, which was assessed by measuring standard length and body weight at regular intervals for 130days. In addition, Specific growth rate (SGR), Fulton's condition factor ( K) and food conversion ratio (FCR) were also calculated as was the effect of salinity on plasma osmolality, blood ion content (Na +, Cl −, K +) and muscle water content at the termination of the experiment. The optimum growth for this study was seen in the lowest salinities at 0 and 4‰. Surprisingly, even small increases in salinity were detrimental to perch growth. At 10‰, growth in terms of body weight was reduced by about 50% after 130days compared to perch reared in freshwater. Interest in brackish water production of perch would be most likely served best by selecting a strain of perch that is adapted to saline conditions, as found in the lower Baltic region. Further studies are required to understand the potential for brackish water perch production.

Influence of Introduced Spawning Habitat on Yellow Perch Reproduction in Lake Madison, South Dakota

ABSTRACT Yellow perch (Perca flavescens Mitchill) populations often exhibit variable recruitment in eastern South Dakota. Lakes with erratic yellow perch recruitment are shallow and lack structure; consequently, habitat manipulation may be useful to enhance perch recruitment. The objective of this study was to determine the contribution of eggs deposited on a conifer tree reef toward overall larval yellow perch production in Lake Madison. The number of egg masses deposited on the reef and the mean number of eggs per mass were calculated and used to estimate the number of larvae produced on the reef. Peak abundance of larvae in the lake was estimated using a surface trawl. Results from two years indicated that the reef contributed 14 to 37% toward larval yellow perch production, although confidence intervals were large. Low numbers of egg masses observed per tree (0.13 to 0.44) relative to other studies lead us to conclude that several smaller reefs might have been a better design than a single, large reef.

Mortality and production of 0+ perch, Perca fluviatilis L., in two Scottish lakes

Mortality of 0+ Eurasian perch was measured directly from the decline in catch in a high‐speed plankton sampler and described by a negative exponential model. A mean mortality of 0.063 day 1 (range=0.020–0.089) was calculated; for 0+ juveniles it was 0.021 day 1. Mean larval production was 0.85–1.30 mg dry weight m−2 day−1 in Loch Kinord and 0.08–0.12 in Loch Davan. Annual production of 0+ juveniles was 1.97–7.55 kg wet weight ha −1 at L. Kinord and 1.01 kg at L. Davan. The contribution of 0+ perch, including the egg stages, to total perch production was 88–96%. Availability of food items on transition to exogenous feeding and through the larval period did not limit survival. Cannibalism by adults accounted for most of larval mortality, and predation by pike and adult perch were responsible for the majority of juvenile losses. The population structure of adult perch, for 12 year classes, was stable at L. Kinord, while year classes at L. Davan exhibited fluctuations in abundance and in two sampling years were eliminated in the first summer. Survival in the eleutheroembryonic phase was variable at L. Davan and observed to be low compared with L. Kinord. It is suggested that this was a result of water turbulence on the exposed and shallow spawning areas at L. Davan.

Electronic structure of ferrocyanide ion calculated by the SCF Xα-scattered wave generalized partitioning method

Eurasian perch (Perca fluviatilis) has been identified as an aquaculture species that can contribute to supply and supplement wild stocks for niche markets in European alpine regions. As a species earmarked for expansion it is important to benchmark the environmental impact associated with its production. The case study site presented a dilemma of opportunity (the dilemma of carrying out a study to inform production processes, at the beginning or development of a product/system or to wait until it is established and in steady state). This dilemma is often a limiting factor in the assessment of emerging systems or products and as a result this site was data deficient in a number of areas (energy use, growth rate and water use) which required the use of an ab initio approach to overcome these gaps. Data for growth, oxygen and heating were modelled for one kilogram of fish to the farmgate for 2018. The generated data was investigated for environmental impact using life cycle assessment (LCA). Impact categories included in the study were global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), freshwater and marine ecotoxicity potential (FAETP and MAETP), cumulative energy demand (CED), net primary production use (NPPU) and water use. The results indicated that there was high variability between the inputs, outputs and impacts associated with the production of perch to the farmgate. The highest variability was observed in live feed use and energy inputs between the batches. This was related to egg quality and the survival rates of the batches. The nursery stage of production was found to have the greatest environmental burden of all stages. EP was dominated by emissions from the stock. Electricity use and feed were the greatest contributors to GWP, AP and FAETP. Electricity and heating had the greatest share of CED and MAETP. Water use (using the AWARE methodology) was dominated by feed production, fish culture and electricity generation. The result of this analysis echoes that of similar studies in that the dominant contributors to the life cycle impacts of RAS products are electricity and feed. This study constitutes the first LCA of perch production in RAS. In addition to this, the study also outlines a framework and methodology, which can be used to overcome the dilemma of opportunity when assessing the environmental burden of an emerging aquaculture system or species. This approach allows operators to overcome data deficits, which may exist and implement impact strategies prior to the finalisation of the process or system.

Lake Erie: Effects of Exploitation, Environmental Changes and New Species on the Fishery Resources

In no other lake as large as Lake Erie (surface area, 25,690 km2) have such extensive changes taken place in the drainage basin, the lake environment, and the fish populations over the last 100 years. Deforestation and prairie burning led to erosion and siltation of valuable spawning grounds. Marsh spawning areas were drained. Lake-to-river spawning migrations were blocked by mill dams. Accelerated cultural nutrient loading increased total dissolved solids by nearly 50% (1920–70). Average summer water temperatures increased 1.1 C. Phytoplankton and zooplankton abundance increased severalfold. Severe oxygen depletion developed in the bottom waters of all three basins of the lake. Lake sturgeon were fished out as nuisance fish in the late 1800s. The commercial fisheries for lake trout, lake whitefish, and lake herring collapsed by 1940 and those for blue pike and walleye by 1960. Yellow perch production became unstable in the 1960s. The effects of exploitation, environmental changes, and new species on these fish population changes are discussed.