Sources of sampling bias in enclosure fish trapping: Effects on estimates of density and diversity

Jacobsen, Terri; Kushlan, James A.

doi:10.1016/0165-7836(87)90055-5

Cited by 25 publications

(25 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Kushlan 1981, Huh 1984, Erwin e t al. 1985, Kushlan et al 1986, Sogard et al 1987, 1989, Holmquist et al 1989a and have been shown to be h~g h l y efficient, relative to other collecting devices, for quantitatively sampling demersal organisms in vegetated habitats (Kushlan 1981, Freeman et al 1984, Jacobsen & Kushlan 1987, Rozas & Minello 1997. Throw trapping of well-separated stations is effectively sampling w~t h replacement (Jacobsen & Kushlan 1987), and re-sampling seagrass-covered sites at 6 mo Intervals over a period of 4 yr does not cause shifts in measures of seagrass cover or assemblages of mobile fauna (Holmquist unpubl.).…”

Section: Methodsmentioning

confidence: 99%

Disturbance and gap formation in a marine benthic mosaic:influence of shifting macroalgal patches on seagrass structure and mobile invertebrates

Holmquist¹

1997

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

A field experiment was used to examine the interactions among structurally complex, spatially shifting structure (macroalgae deposited by currents), less-complex stationary structure (seagrass), and mobile benthic invertebrates. I tested the effect of drift algal patches on underlying seagrass structure and fauna by establishing manipulated algal mats over seagrass for comparison with control seagrass plots. Control and experimental plots did not differ significantly for any variable prior to algal addition, but most seagrass structure was removed by this disturbance over a 6 mo period. In contrast. abundance of mobile fauna on experimental plots increased after 6 mo of algal cover relative to abundance on control plots. There was also greater evenness in the canopy fauna of the algal plots which contrasted with the high level of dominance apparent on control plots. Although the structurally complex mats formed by drifting algae provided short-term habitat enhancement for some fauna, longterm effects on fauna are probably negative due to mat ephemerality and degradation of seagrass.

show abstract

Section: Methodsmentioning

confidence: 99%

Disturbance and gap formation in a marine benthic mosaic:influence of shifting macroalgal patches on seagrass structure and mobile invertebrates

Holmquist¹

1997

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

show abstract

“…Enclosure traps, including drop-traps (Kahl 1963;Kushlan 1974;Gilmore et al 1978;Pihl and Rosenberg 1982;Pihl Baden and Pihl 1984;Nellbring 1985), drop-nets (Hellier 1958;Mosely and Copeland 1969;Kjelson et al 1975;Adams 1976), buoyant pop-nets (Larson et al 1986;Serafy et al 1988;Dewey et al 1989;Connolly 1994), lift-nets (Higer and Kolipinski 1967;Rozas 1992), and throw-traps (Kushlan 1981;Jacobsen and Kushlan 1987;Chick et al 1992;Jordan et al 1997), provide instantaneous samples and are considered to be the most efficient sampling devices for small fishes and invertebrates in shallowwater habitats less than 1.5 m deep (Kushlan 1981;Jordan et al 1997). But only a few complex and labor-intensive buoyant drop-and pop-nets with floating frames are usable at depths of 2 to 5 m (Mosely and Copeland 1969;Larson et al 1986;Serafy et al 1988).…”

Section: Introductionmentioning

confidence: 99%

“…Traps that rapidly enclose a clearly defined area have been increasingly used to sample fish populations in shallow-water habitats because they are a precise and accurate means to obtain quantitative estimates of fish assemblage abundance and biomass in vegetated habitats (Kushlan 1981;Jacobsen and Kushlan 1987;Jordan et al 1997). The absolute efficiency of drop traps can be estimated in shallow block net separated areas with known fish densities (Kushlan 1981;Jordan et al 1997), and they have often been used to estimate the relative efficiency of seines and trawls (Freeman et al 1984;Dewey et al 1989;Wennhage et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Comparison of an enclosure drop trap and a visual diving census technique to estimate fish populations in eelgrass habitats

Bobsien

Brendelberger

2006

Limnology & Ocean Methods

View full text Add to dashboard Cite

In shallow vegetated aquatic habitats exceeding 2 m depth, conventional methods to determine fish abundances are of limited success. In this study, the sampling qualities of 2 methods for investigating the fish community associated with the eelgrass Zostera marina were tested: a newly developed enclosure drop trap (ET) operated from the water surface and a visual diving strip transect technique. The construction and the sampling procedure of the enclosure trap are described in detail. Both sampling procedures were performed simultaneously at the same eelgrass sampling site at depths between 2 and 5 m. The comparison revealed deficiencies in relative catch efficiency for both methods. Limitations with respect to bottom-dwelling forms are obvious for the ET and with respect to the Syngnathidae and Gasterosteidae for the visual diving census. Abundance estimates of pelagic, schooling species were highly variable with both methods. Correction coefficients for the different behavioral categories of eelgrass fish were calculated. The fish species composition showed good agreement between the 2 methods, but the number of species on each sampling occasion was consistently higher in the ET catches. The length class frequency distributions estimated by the divers corresponded approximately with direct measurements of fish from the ET catches. The methods complemented one another and can be recommended for simultaneous deployment to get accurate quantitative estimates of eelgrass fish populations. The relative capture efficiency of the enclosure trap can be incorporated to improve abundance measurements of small fish in Zostera marina beds without the help of divers.

show abstract

“…For example, fish trapping can underestimate fish densities (Jacobsen and Kushlan 1989) and result in selective sampling of communities (Ovegard et al 2011), while baited remote underwater video surveillance can attract greater numbers of predatory and scavenging species (Harvey 2007) and converting counts to density data can be difficult (Miller and Hunte 1987). Using the same technique in different habitats or times of the year, however, facilitates insights into relative abundance and distribution providing the particular method employed is not biased by the differences presented by contrasting habitats or seasons.…”

Section: Introductionmentioning

confidence: 99%

“…Multiple techniques are used to investigate fish abundance and distribution, including seining, trawling, fish trapping, visual census and underwater video surveillance (Munro 1974, Jacobsen and Kushlan 1989, Collins 1990, Travers and Potter 2002, Edgar et al 2004, Harvey et al 2007), all of which have their own biases. For example, fish trapping can underestimate fish densities (Jacobsen and Kushlan 1989) and result in selective sampling of communities (Ovegard et al 2011), while baited remote underwater video surveillance can attract greater numbers of predatory and scavenging species (Harvey 2007) and converting counts to density data can be difficult (Miller and Hunte 1987).…”

Section: Introductionmentioning

confidence: 99%

The Role of Teleost Grazers in a Relatively Pristine Seagrass Ecosystem

Bessey

View full text Add to dashboard Cite

All rights reserved.iv ACKNOWLEDGMENTS I would like to thank the numerous professors, assistants, colleagues, collaborators, businesses, and agencies in both the United States and Australia that have provided support, guidance, opportunities, and stimulating scientific discussions. It would be desirable to acknowledge each and every one by name, but to do so may lead to omissions that I would regret. However, I would like to specifically thank my major professor, Dr. Michael R. Heithaus. He provided me with not only the opportunity to accomplish a goal that I had pondered for over a decade, but also the support, guidance and funding to successfully complete that goal. The professional and personal outcomes Trophic downgrading of ecosystems necessitates a functional understanding of trophic cascades. Identifying the presence of cascades, and the mechanisms through which they occur, is particularly important for seagrass meadows, which are among the most threatened ecosystems on Earth. Shark Bay, Western Australia provides a model system to investigate the potential importance of top-down effects in a relatively pristine seagrass ecosystem. The role of megagrazers in the Shark Bay system has been previously investigated, but the role of macrograzers (i.e., teleosts), and their importance relative to megagrazers, remains unknown. The objective of my dissertation was to elucidate the importance of teleost macrograzers in transmitting top-down effects in seagrass ecosystems. Seagrasses and macroalgae were the main food of the abundant teleost Pelates octolineatus, but stable isotopic values suggested that algae may contribute a larger portion of assimilated food than suggested by gut contents. Pelates octolineatus is at risk from numerous predators, with pied cormorants (Phalacrocorax varius) taking the majority of tethered P. octolineatus. Using a combination of fish trapping and unbaited underwater video surveillance, I found that the relative abundance of P. octolineatus was vi greater in interior areas of seagrass banks during the cold season, and that the mean length of P. octolineatus was greater in these areas compared to along edges of banks.Finally, I used seagrass transplants and exclosure experiments to determine the relative effect of megagrazers and macrograzers on the establishment and persistence of three species of seagrasses in interior microhabitats. Teleost grazing had the largest impact on seagrass species with the highest nutrient content, and these impacts were primarily observed during the warm season. My findings are consistent with predictions of a behaviorally-mediated trophic cascade initiated by tiger sharks (Galeocerdo cuvier) and transmitted through herbivorous fishes and their predators. bed, where each site contains megagrazer treatment plots that A) are full controls; no exclusions, B) megagrazers no excluded, and C) megagrazers excluded. Each plot was 2.6 x 3.0m, which consisted of nine 30cm x 30cm macrograzer treatment subplots, spaced 50cm apart. Macrograzers exclusion cage (ME) ...

show abstract

Sources of sampling bias in enclosure fish trapping: Effects on estimates of density and diversity

Cited by 25 publications

References 12 publications

Disturbance and gap formation in a marine benthic mosaic:influence of shifting macroalgal patches on seagrass structure and mobile invertebrates

Disturbance and gap formation in a marine benthic mosaic:influence of shifting macroalgal patches on seagrass structure and mobile invertebrates

Comparison of an enclosure drop trap and a visual diving census technique to estimate fish populations in eelgrass habitats

The Role of Teleost Grazers in a Relatively Pristine Seagrass Ecosystem

Contact Info

Product

Resources

About