Faculty Profile



Center for Inland Waters

Ralf Riedel



Adjunct Professor of Biology

M. S. in Fishery Science and Technology, University of Rhode Island
Emphasis: Selectivity of fish harvesting gears

Ph.D in Ecology
University of Illinois U/C
Emphasis: Management of natural resources

B.S. in Fisheries Engineering
University of Pernambuco
Emphasis: Design of fish harvesting gears.

tel. 619-594-0994

fax 619-594-5676



My professional interest include research and teaching. My research interests are described below. The interaction with students and the potential for contributing to environmental literacy motivate my desire for teaching.

Main Research Interest

I am mainly interested in investigating the effects of fisheries on ecosystems. Most of our research effort has been directed at maximizing yields without much emphasis on the consequences that actions towards yield maximization will have on the ecosystem. I am interested in addressing the effects of current fishing practices because they may lead to irreversible consequences that are detrimental to marine systems.

I have worked in the fishing industry and realized first hand how damaging most fishing practices can be. Bottom trawling may affect the benthos either directly (resuspending the sediment, scraping the floor, or destruction of benthos) or indirectly (mortality of fish and long-term changes to the benthos). Complexity and biodiversity may be reduced and ecological services compromised when biogenic and sedimentary structures on fishing grounds are altered. Reduced habitat complexity may also increase vulnerability of exploited species to predation.

Removal of top predators by pelagic gear may affect the abundance of the remaining organisms and the equilibrium of the ecosystem. As an example, the incidence of shark bycatches in fisheries such as long-lines for tuna and billfishes may impact the ecosystem irreversibly and possibly affect catches of commercially important species. Similarly, the bycatch from small-meshed trawlers may cause a shift in community structure favoring non-commercial species.

There is little information on the impact of fishing on non-commercial species. Altering the basic productivity and structure of the ecosystem by harvesting a fraction of the biota may be a reason why we have been faced with so much uncertainty in fisheries management. Incorporating the various components of the ecosystem when managing fisheries resources may improve our understanding of fluctuations in fish abundance and be a step toward resource sustainability.

The management of fisheries within ecological principles by managing the ecosystem may provide a better alternative to resource sustainability. Ecosystem management is an all-inclusive, possibly more stable alternative to current management practices. If ecosystem management is to be successful, experiments are required of the fishing effects on habitat and species structure in an attempt to address the interconnections of marine systems.

Compromising the ecosystem to attain management goals is short-sighted to say the least. Given the current human population explosion the oceans will not be a solution to our protein problems. Overexploiting our oceans based on our putative needs will only aggravate the ecological problems we are now facing.

Quantitative Fisheries

-Evaluation of anthropogenic and environmental effects on fish populations.
-Relative effects of environmental and anthropogenic factors to evaluate the degree of uncertainty when managing fish stocks.
-Simulation models for stock assessment and sustainable management.

Marine Ecology

-Inter-intraspecies interactions.
-Predator/prey as related to fisheries - trophodynamics.
-Direct and indirect effects on ecosystems of predator or prey removals (as when overfishing takes place).
-Life-history of alternative fishery resources.

Fish Behavior

-Fish migration and spatial/temporal distribution (Seasonal and diel migrations of fish; larval distributions according to environmental factors).
-Fish behavior in the vicinity of harvesting gears.
-Selection of fish harvesting gears.


DeAlteris, J. and R. Riedel. 1996. Effect of size selection within and between fishing gear type on the yield and spawning biomass per recruit and catch per unit of effort for a cohort of an idealized ground fish. Journal of the Northwestern Atlantic Fishery Science 19:73-82.

Perea, P., S. Sobaski, P. Bayley, R. Riedel, and D. Philipp. 1996. Database management and analysis of fisheries in Illinois lakes: optimizing fisheries management. Volume 1 Federal Grant F-69-R-(7-9).

Riedel, R. and J. DeAlteris. 1995. Factors affecting the performance of the nordmore grate system: a bycatch reduction device used in the Gulf of Maine shrimp fishery, Fisheries Research 24:181-198.

Riedel, R., P. Bayley, and D. Austen. Power analysis for annual variations in largemouth bass abundance using a temporally and spatially large-scale data set: years-as-replicate vs. lakes-as-replicate approaches. Transaction of the American Fisheries Society. (In Press)

Riedel, R., P. Bayley, and D. Austen. Influences of environmental effects on the dynamics of largemouth bass. Canadian Journal of Fisheries and Aquatic Sciences. (In Press)

Riedel, R., P. Bayley, and D. Austen. Effects of sport fisheries management in Illinois in determining largemouth bass fluctuations. North American Journal of Fisheries Management. (In Press)

Riedel, R., P. Bayley, and D. Austen. Effects of water level fluctuations on growth of largemouth bass: a management alternative for mimicing flood pulses in artificial lakes. North American Journal of Fisheries Management. (In Press)

Riedel, R., P. Bayley, and D. Austen. Variation in lake production for largemouth bass: the usefulness of morphoedaphic factors. Limnology and Oceanography. (In Press)

Professional Experience

I recently accepted a position at San Diego State University studying the Salton Sea ecosystem, a saltwater lake of economic and ecological importance in California. The salinity of the lake has been increasing during the last several years and the success of restoring the lake is intimately linked to understanding the ecology of the various components of its fauna and flora. The lake is a bird sanctuary, providing one of the last remaining stopover for migratory species of birds, some of them endangered, like the brown pelican. The lake also provides the last refuge for the endangered desert pupfish and possibly the razorback sucker.

I have recently completed my work at the Illinois Natural History Survey (INHS). At the INHS, my duties were to compile and analyze a statewide database for management activities and fish sampling conducted over the last 30 years in Illinois state managed lakes. This work involved: 1. working with all Illinois district fisheries biologist in collecting pertinent data for an evaluation of management practices; 2. performing analyses to model and investigate the effects of natural and man-made factors on the dynamics fish populations; 3. developing computer programs to handle and store large amounts of data; 4. physically organize all information collected. I was also involved in the mapping and digitizing of Illinois lakes for determination of lake morphometry, and land-use patterns.

Teaching Experience

Course: Computer Applications in Fishery Science.
Description: this course covered the use of statistical and fisheries software, it introduced students to computer programming, and to the functioning of computer hardware.
Period: Spring 1993.

Course: Genetics, Evolution, and Biodiversity.
Description: this course covered molecular and population genetics, evolution, and plant/animal ecology and anatomy.
Period: Fall 1996, Spring and Fall 1998.

Professional Experience

University: San Diego State University
Position: Adjunct Faculty.
Period: 1999 -

Company: On-The-Job Consulting
Position: Web page developer (ASP, CGI, Perl, Java, SQL).
Period: 1998 - 1999

Company: Illinois Natural History Survey
Position: Research assistant.
Period: 1993 - 1998

Company: CEBEL
Position: Software developer (C and Clipper) and system analyst.
Period: 1988 - 1990

Company: Kowalsky Ind. Pescados S/A
Position: Crew member in the shrimp trawling, sardine purse seining, and pair bottom trawling fisheries.
Company: Norte Pesca S/A
Position: Crew member in the surface longlining fishery.
Company: Katsushio Suisan Kabushiki Kaisha
Position: Gear Technologist in the skipjack pole-and-line- fishery.
Period: 1986 - 1989