Effects of water abstraction
The density of the two species was noticeably higher in the perennial reaches. Chub was the species most affected by water abstraction, and this caused its disappearance from a long intermittent reach where it was present historically [14, 43]. However, more significant effects of water abstraction for other variables were obtained for barbel because it is more widespread in the basin, whereas chub is only present in some stream segments. Several cases of flow reduction have been associated to decreased fish abundance (e.g. [15, 65, 66]), as well as recent fish population contractions or local extinctions related to hydrologic alteration in the Tordera catchment [14, 67–69]. Considerable numbers of dead fish of several species (including the two study species as well as brown trout and Phoxinus sp.) were directly observed during the study period, mostly in reaches immediately after pool drying. On the other hand, high densities of barbel, with occasional presence of chub, were detected in pools persisting during summer, suggesting the existence of a drought-escape behavior for these fishes. This behavior has been described in regions affected by dry summers, where the initial phase of drying may promote fish movement [70–72]. These observations allowed us to recognize streambed dryness as a leading cause of low fish density in these reaches, associated to death and migration [13, 73].
Natural variation in fish longitudinal distribution can in part explain the observed pattern of barbel and chub survival, since lower reaches have in general more stable ecological conditions, are nutrient-rich and show higher water temperatures than the uppermost ones [74, 75]. In particular, the middle reaches showed the highest fish densities, probably because of both perennial flow regime but also because the higher nutrient input increases ecosystem productivity. Chub, moreover, is known to colonize preferentially deep pools and runs , and riffles are the most common habitat in the upper course of Tordera and Arbúcies, where few individuals of this species were found.
We are confident that the effects of water abstraction on fish abundance are real and not due sampling issues for a number of reasons. Although the two lowermost sites had larger wetted widths (but depths much less that the maximum depth in most of channel) during one of the samplings (during a high flow), 13 out of 15 sampling sites had widths much less than 15 m, and thus the European Standard on electrofishing (EN 14011), which requires a minimum length of 50 m to assess fish abundance and age structure, was always followed. The length of 100 m that we used everywhere might have been less adequate to estimate fish richness and species composition in a few occasions  but should not affect individual level metrics, such as condition or individual growth. In all sites, depth was always less than 75 cm (often much less) and thus electrofishing efficiency was high. More importantly, a concurrent mark-recapture study, which is arguably the best method available for this purpose, confirmed the effects of water abstraction on fish abundance .
Effects of water intermittency at individual level
Our observations confirmed the presence of smaller individuals of barbel and chub in the Tordera intermittent reaches . This pattern may be due to three possible factors: i) high mortality rates in intermittent sites, that imply lower probabilities for fish to live many years and attain large sizes; ii) higher mobility of larger individuals, potentially more capable to move away from impacted reaches [34, 72]; and iii) size-selective mortality due to physiological stress, which is known from Barbus, Squalius and other Mediterranean cyprinid species as a consequence of flow intermittency [34, 35, 76, 77] because of higher oxygen demand of larger individuals [78, 79].
Fish condition and growth were expected to vary across sites and seasons, and to be lower in the intermittent reaches. Such a response to low flow conditions has been reported for barbel Luciobarbus sp. (e.g. [17, 32, 33]), salmonids (e.g. [20, 79]), and smallmouth bass . Our observations partially confirmed our hypothesis. Growth, measured as length-at-age, was lower at intermittent reaches for both chub and barbel. Scale increments showed slightly different results (lower for barbel but higher for chub at intermittent reaches), possibly because increments in calcified structures are not always well correlated with growth rates  and because the models used for scale increments average increases in many growing seasons and not final size-at-age and account for many other factors (e.g. year and individual). Surprisingly, barbel from intermittent reaches showed better condition (weight-length relationship), comparable with the ones from the urbanized reaches in the middle Tordera course, in which fish of the two species looked healthy and abundant. Another study  reports both higher condition and growth of cyprinids in sites affected by summer dryness. Barbel populations from permanent streams, moreover, have been reported to show a slender body profile and lower condition than populations from intermittent streams, a likely adaptation to higher flow and water velocity . Fish inhabiting instable environments like intermittent streams may require high levels of energy reserves, i.e. high body condition, a likely investment to increase reproductive success [18, 19, 82, 83]. These independent evidences cannot exclude that high barbel condition in the Tordera intermittent reaches may also depend on adaptive phenotypic plasticity. In several other cases, by contrast, barbel condition was reported to be positively correlated to riparian vegetation cover, water flow and related environmental variables, such as conductivity and oxygen concentration (e.g. [16, 17, 32, 33, 84]). Mas-Martí et al.  attributed the lower condition of B. meridionalis and S. laietanus in an intermittent tributary of the Tordera to two main factors, namely the lower temperature and productivity of the tributary, and bottom-up effects of stream dryness on the trophic web, leading to lower food availability for fish. In our case, part of the upper intermittent reach was covered by a dense tree canopy, which coupled with hyporheic flow kept temperature and dissolved oxygen within tolerable levels, mitigating the physiological stress for fish. Moreover, strong competition for food was limited to some weeks in the summer refugia, but high invertebrate availability per capita could be guaranteed in the other seasons for the few fish that survived drying. Alternatively, fish with better condition might be more capable of recolonizing intermittent reaches. Overall, dryness increases mortality and decreases abundance and growth but fish present may show better individual condition due to better colonization capability or reduced resource competition.
Chub was usually present, at low densities, in only one of the intermittent sampling reaches, the lowermost one, making difficult to compare traits among impacted and control sites. Our results show a gradual condition decrease from the most urbanized sites to the lowermost, intermittent one, rather than a simple distinction between sites with different flow regimes. In fact, most life-history traits showed variation, often non-linear, with altitude, which had to be accounted to adequately test the effects of flow regime. Density, growth, and condition of barbel were highest at intermediate altitudes. These patterns have been observed in many freshwater fishes but might also be due in part to anthropogenic factors. The middle reaches of the Tordera mainstem are a nutrient-rich zone affected by WWTP effluents [41, 42]. These findings contrast with those of Britton et al. , who found higher Barbus growth rates in presence of low phosphate loads, but match observations with other European cyprinids such as Rutilus rutilus (e.g. [85, 86]). Arguably, a moderate nutrient enrichment in the middle Tordera course may increase barbel growth and condition if they do not exceed the tolerance limits of this species. In agreement, age at length of barbel and scale increments for both species were high in the more eutrophic site T8.
The growth-at-age of the two species may reflect sexual maturation. This occurs at age 1 for most individuals of barbel, whereas in chub it is more variable  and may correspond to the first growth decrease observed after the second year of life [87, 88]. Furthermore, as chub is a multiple spawner with reproductive season potentially protracted  we cannot exclude that a significant fraction of the newborns hatch at the beginning of an unfavorable period, resulting in low growth rates in the first year [88–91]. Chub size increment was higher in warmer years: this was expectable, since temperature is a dominant factor, together with food availability, in determining fish growth patterns in space and time (e.g. [87, 88]).
Our research confirmed the existence of strong effects of hydrologic alteration at the population and individual levels for the two study species. Population and individual metrics showed highest values in the middle Tordera course, where flow is permanent and nutrient availability is higher due to WWTP inputs. Body condition was not negatively affected by stream drying, revealing how individual traits vary in the potential to inform about hydrological regime disruption. Finally, it is important to stress how the effects of drying were often highlighted only after controlling for natural variability through appropriate statistical tools. Chub was the species most affected by drought, being absent from most impacted sites. Barbel seemed better adapted to take advantage of moderate environmental disturbance, probably through increased resistance and colonization ability, except in extreme situations in which it is wiped away. We would expect this species to recover quickly in terms of abundance in the intermittent reaches if drought events were less intense and lasting, whereas chub was revealed as more sensitive to reduced stream flow and less resilient to hydrologic alteration.
These materials were made possible thanks to the generous support from the Kemper K. Knapp Bequest Committee.
On this page, the UW-Madison Writing Center Writer's Handbook offers advice on writing abstracts and answers questions such as: including:
On the "Abstracts: Examples" page, you will also find sample Undergraduate Symposium abstracts from a variety of disciplines.
What is an abstract?
An abstract is a concise summary of a larger project (a thesis, research report, performance, service project, etc.) that concisely describes the content and scope of the project and identifies the project’s objective, its methodology and its findings, conclusions, or intended results.
Remember that your abstract is a description of your project (what you specifically are doing) and not a description of your topic (whatever you’re doing the project on). It is easy to get these two types of description confused. Since abstracts are generally very short, it’s important that you don’t get bogged down in a summary of the entire background of your topic.
As you are writing your abstract, stop at the end of every sentence and make sure you are summarizing the project you have undertaken rather than the more general topic.
Do abstracts vary by discipline (science, humanities, service, art, or performance)?
Abstracts do vary from discipline to discipline, and sometimes within disciplines.
Abstracts in the hard sciences and social sciences often put more emphasis on methods than do abstracts in the humanities; humanities abstracts often spend much more time explaining their objective than science abstracts do.
However, even within single disciplines, abstracts often differ. Check with a professor to find out about the expectations for an abstract in your discipline, and make sure to ask for examples of abstracts from your field.
What should an abstract include?
Despite the fact that abstracts vary somewhat from discipline to discipline, every abstract should include four main types of information.
What should my Objective/Rationale section look like?
What is the problem or main issue? Why did you want to do this project in the first place?
The first few sentences of your abstract should state the problem you set out to solve or the issue you set out to explore and explain your rationale or motivation for pursuing the project. The problem or issue might be a research question, a gap in critical attention to a text, a societal concern, etc. The purpose of your study is to solve this problem and/or add to your discipline’s understanding of the issue.
Some authors state their thesis or hypothesis in this section of the abstract; others choose to leave it for the “Conclusions” section.
What should my Methods section look like?
What did you do?
This section of the abstract should explain how you went about solving the problem or exploring the issue you identified as your main objective.
For a hard science or social science research project, this section should include a concise description of the process by which you conducted your research. Similarly, for a service project, it should outline the kinds of service you performed and/or the process you followed to perform this service. For a humanities project, it should make note of any theoretical framework or methodological assumptions. For a visual or performing arts project, it should outline the media you employed and the process you used to develop your project.
What should my Results/Intended Results section look like?
What did you find?
This section of the abstract should list the results or outcomes of the work you have done so far. If your project is not yet complete, you may still want to include preliminary results or your hypotheses about what those results will be.
What should my Conclusion section look like?
What did you learn?
The abstract should close with a statement of the project’s implications and contributions to its field. It should convince readers that the project is interesting, valuable, and worth investigating further. In the particular case of the Undergraduate Symposium, it should convince readers to attend your presentation.
How should I choose my title?
You probably already have some idea for a title for your project. Consider your audience; for most projects, it is best to choose a title that is comprehensible to an audience of intelligent non-specialists.
Avoid jargon; instead, make sure that you choose terms that will be clear to a wide audience.
What my project isn't finished? What if my results didn’t turn the way I expected?
More often than not, projects are not completely finished by the time presenters need to submit their abstracts. Your abstract doesn’t need to include final results (though if you have them, by all means include them!).
If you don’t yet have final results, you can either include any preliminary results that you do have, or you can briefly mention the results that you expect to obtain.
Similarly, unexpected or negative results occur often. They can still be useful and informative, and you should include them in your abstract. Talk with your mentor to discuss how such results are normally handled in your discipline.
In any case, whether you have complete, partial, projected, or unexpected results, keep in mind that your explanation of those results – their significance – is more important than the raw results themselves.
How can I fit all of this into just 125 words?
Bestraightforward. Don’t worry about making your abstract “flow”. Don’t worry about writing a long or elaborate introduction or conclusion, and as we suggested above, don’t include too much background information on your project’s general topic. Instead, focus on what you have done and will do as you finish your project by providing the information we have suggested above.
If your abstract is still too long, look for unnecessary adjectives or other modifiers that do not directly contribute to a reader’s understanding of your project. Look for places where you repeat yourself, and cut out all unnecessary information.
How should I start writing my abstract?
Re-examine the work you have done so far (whether it is your entire project or a portion of it). Look specifically for your objectives, methods, results, and conclusions.
After re-examining your work, write a rough draft without looking back at the materials you’re abstracting. This will help you make sure you are condensing the ideas into abstract form rather than simply cutting and pasting sentences that contain too much or too little information.
Bring your draft to the Writing Center to get feedback from a writing instructor. Call 263-1992 to make an appointment.
What stylistic techniques will make my abstract most effective?
Avoid jargon. Jargon is the specialized, technical vocabulary that is used for communicating within a specific field. Jargon is not effective for communicating ideas to a broader, less specialized audience such as the Undergraduate Symposium audience.
Discipline-specific sentence: Hostilities will be engaged with our adversary on the coastal perimeter.
Revised for a more general audience: We will fight on the beaches.
Discipline-specific sentence: Geographical and cultural factors function to spatially confine growth to specific regions for long periods of time.
Revised for a more general audience: Geographical and cultural factors limit long-term economic growth to regions that are already prosperous.
Discipline-specific sentence: The implementation of statute-mandated regulated inputs exceeds the conceptualization of the administrative technicians.
Revised for a more general audience: The employees are having difficulty mastering the new regulations required by the law.
(Examples excerpted from Lantham, Richard. Revising Prose; McCloskey, Donald N. The Writing of Economics; and Scott, Gregory M. and Garrison, Stephen M., The Political Science Student Writer’s Manual.)
Be concise. Don’t use three words where you can communicate the same idea in one. Don’t repeat information or go into too much detail. Don’t just cut and paste sentences from your research paper into your abstract; writing that is appropriate for long papers is often too complicated for abstracts. Read more about general principles of writing clear, concise sentences.
Useshort, direct sentences. Vary your sentence structure to avoid choppiness. Read your abstract aloud, or ask someone else to read it aloud to you, to see if the abstract is appropriately fluid or too choppy.
Usepast tense when describing what you have already done.
Check with a professor in your field to determine whether active or passive voice is more appropriate for your discipline. Read more about active and passive voice.
Don’t cite sources, figures, or tables, and don’t include long quotations. This type of material takes up too much space and distracts from the overall scope of your project.
What kind of feedback should I seek to make sure my abstract is effective?
Work with a professor or another student in your field throughout the entire process of writing your abstract. People familiar with work in your field will be able to help you see where you need to say more and where you need to say less and will be able to help with clarity and precision as well.
Bring your draft to the Writing Center to get feedback from a writing instructor. Call 263-1992 to set up an appointment.
Finally, ask someone you know (a roommate, friend, or family member) who specializes in a different field to read your abstract and point out any confusing points. If you can make your abstract understandable to an intelligent non-specialist, you’ve probably made it effective for the audience of a standard conference or symposium.
Continue reading for examples of abstracts from many disciplines.
(Works Consulted: LEO Writing Abstracts, ©1995, ‘96, ‘97, ’98 The Write Place; Writer’s Workshop, University of Illinois, Urbana, adapted by Kitty O. Locker, 1997.)