Comparison of the Species Composition, Catch Rate, and Length Distribution of the Catch from Trap Nets with Three Different Mesh and Throat Size Combinations

Abstract

Trap nets of varying design are commonly used to assess fish populations, but the effect of the design on gear selectivity is not well known. In particular, it may be advantageous to use multiple net designs with different mesh and throat sizes to maximize the catch of specific length-classes and to minimize the risk of predation on small fish by larger fish. We compared the species composition, catch rate, and length distribution of fishes caught by three trap net designs with dimensions differing only in mesh size and throat size (0.6-cm delta mesh and 3.8-cm ϫ 3.8cm square throats, 1.3-cm square mesh and 7.6-cm ϫ 7.6-cm square throats, or 2.5-cm square mesh and 12.7-cm ϫ 12.7-cm square throats). A total of 3,473 fish of 18 species were captured from Sandy Lake, Portage County, Ohio, during 24 sample dates from June to August 1999. The large net design had a significantly higher average number of species captured (mean ϭ 11) than the medium or small net design (means ϭ 9 and 8, respectively). Whereas nets with larger mesh and throat size combinations typically caught larger fish for the six most commonly captured species, only rarely did nets capture fish as large or as small as possible based on their physical dimensions. Specific length-classes of some species were not captured in the nets or were very net design specific, indicating a possible difference in trap net vulnerability of different ontogenetic stages. We conclude that data from trap nets with different mesh and throat sizes should not be directly compared with each other, and that multiple net mesh and throat sizes (or even multiple gear types) should be used when a more complete picture of fish length and abundance is desired.

A comparison of the relative efficiency of ring, fyke, fence nets and beam trawling for estimating key estuarine fishery populations

“…Our results support the recommendations of Van Den Avyle et al (1995) that the preferred method of sampling will depend on the fish size-range and habitat being sampled. We also agree with Shoup et al (2003), that multiple gear types are preferable when sampling to assess size-frequency or abundance estimates, and Krause et al (2002) that sampling should be carried out over a range of seasons to reduce estimate error.…”

“…Several authors attribute the bias to fish escapement (Jacobsen and Kushlan, 1987;Losanes et al, 1992;Bayley and Herendeen, 2000). Others (Allen et al, 1992;Shoup et al, 2003) have attributed the bias to avoidance behaviour, particularly by larger fish. In our study, large sea mullet (Mugil cephalus) were observed to leap over the net during setting on several occasions.…”

“…Pepin and Shears (1997) recommended an intuitively common sense approach to sampling of only using gear types with lower variability. However, Shoup et al (2003) observed that a single gear type or mesh size would provide a skewed view of fish length-distributions for some species. Our results support the recommendations of Van Den Avyle et al (1995) that the preferred method of sampling will depend on the fish size-range and habitat being sampled.…”

Monitoring small fish populations in streams: A comparison of four passive methods

“…Shoup et al (2003) advised against the value of comparing population or community structure data that had been obtained by different passive methods. PM traps are the most easily repeatable, as well as the cheapest, among the four trap types employed.…”

Use of Mini‐Fyke Nets for Sampling Shallow‐Water Fish Communities in Florida Lakes

“…Gear configuration, such as different fyke net meshes and shape (e.g., Krueger et al 1998;Shoup et al 2003), has previously been studied. However, the effect of different gear deployments on catch and resulting fish community descriptors, especially in areas with a diversity of habitats, has not been fully explored.…”