1 Present address: Department of Zoology, Oregon State University, Corvallis, OR 97331-2914, U.S.A.. 2 Present address: Department of Biology, University of California, Santa Cruz, CA 95064, U.S.A. .... This is best achieved when the fish.
Environmental Biology of Fishes 51: 111–115, 1998. 1998 Kluwer Academic Publishers. Printed in the Netherlands.
BINCKE: a highly efficient net for collecting reef fishes Todd W. Anderson1 & Mark H. Carr2,3 Present address: Department of Zoology, Oregon State University, Corvallis, OR 97331-2914, U.S.A. 2 Present address: Department of Biology, University of California, Santa Cruz, CA 95064, U.S.A. 3 Correspondence to M.H. Carr (e-mail: carr6biology.ucsc.edu)
1
Received 2.11.1996
Accepted 1.3.1997
Key words: coral reefs, fish collection, kelp forests, methods, SCUBA, structurally complex environments Synopsis The efficient collection of fishes from structurally complex environments (e.g., coral reefs, kelp forests) is difficult because conventional collecting methods generally cannot be used and many of the fishes are mobile and active. We describe the design, operation, and application of a diver-propelled net for efficiently collecting many species of benthic fish that reside on coral reefs and on kelp-forested rocky reefs. The overall size of the net and mesh size of the netting can be adjusted according to the size and behavior of targeted species to minimize drag and damage to specimens. Altering these dimensions combined with proper use of the net can result in a high rate of capture success.
Introduction Collecting organisms from their natural habitats is critical to a variety of studies ranging from systematics and genetics to physiology and ecology. For reef fishes, advances in such studies have been hindered by the difficulty in efficiently collecting live, undamaged specimens from structurally complex environments. For example, the increasing interest in recruitment of early life stages to local fish populations has prompted the need to collect small, elusive, and sometimes cryptic individuals. Various collecting methods have been developed, most of which are time-consuming and labor-intensive; these include hand nets, traps, drop nets, and the use of anesthetics (Coyer & Witman 1990). To efficiently collect large numbers of fishes associated with structural features (e.g., corals, macroalgae) of reef habitats, we have developed a net specifically designed for use with SCUBA. This net was initially
developed to collect recently settled rockfishes (Scorpaenidae) from kelp-forested rocky reefs for taxonomic (Anderson 1983), diet (Singer 1985), and recruitment (Carr 1991) studies. Subsequently, it has proven useful for collecting all life intervals of several species from temperate (Carr 1989, 1994, Anderson 1994, Anderson & Sabado 1995, Behrents-Hartney 1997) and tropical (Carr & Hixon 1995, Forrester unpublished, Hixon & Carr unpublished) regions. It is particularly effective for collecting species that aggregate in the water column adjacent to structure, but less effective for solitary cryptic species that maintain contact with the substratum. Because of its wide success in collecting fishes on both coral reef and kelp-forested rocky reefs, this net is referred to as the Benthic Ichthyofauna Net for Coral/Kelp Environments (BINCKE). Although the BINCKE is not the first diver-operated net for collecting small reef fishes (e.g., McCleneghan & Houk 1978), its ease of oper-
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112 ation and versatility make it a significant improvement over previous designs. Here we describe the design, operation, and application of the BINCKE.
Net design The basic design of the BINCKE is a rectangular net opened and closed by means of a rigid, hinged frame at one end (Figure 1). The size of the BINCKE, determined by the dimensions of the frame (height and width) and length of the netting (depth), should vary depending upon the size and behavior of targeted species. The frame dimensions and length of netting determine the gape of the net and capture volume, respectively. Frame dimensions and length of netting increase for collection of larger individuals or aggregations and for more actively swimming species. Typically, the rectangular frame has a height-to-width ratio of 1 : 2 with height ranging in size from 0.75 m to 1.0 m. Netting length typically varies with frame height in a ratio of 1 : 3 (height to length). Drag (resistance to moving the net through the water) increases substantially with both frame size and netting length. Thus, collection of more actively swimming species is made more difficult with a larger BINCKE and the net’s dimen-
Figure 1. Design of the Benthic Ichthyofauna Net for Coral/Kelp Environments (BINCKE). Illustration is to scale.
sions should be altered accordingly. Because mesh size also influences drag, it may be necessary to alter height-to-length ratios for different mesh sizes. Square mesh size is critical for retention of specimens and as it influences drag. Smaller mesh sizes are required for collecting small fishes and to minimize damage to specimens. However, drag is inversely related to mesh size such that capture success declines with decreasing mesh size. Thus, optimal mesh size is achieved by using the smallest mesh size that will allow sufficient net speed to capture fleeing fish. In addition, smaller mesh is more visible and therefore more easily avoided, especially by actively swimming fishes. Because dark-colored netting is less visible, greater capture success can be achieved by dyeing the netting to a dark green, dark blue, dark red or black color. Typically, square mesh size (mm) ranges from a minimum of 1.5 mm for collecting recently settled early juveniles, up to 25 mm for many adult reef fishes (Table 1).
Materials and construction The frame is constructed from 12.5 mm outside diameter Schedule 40 polyvinyl chloride (PVC) pipe. Holes (6 mm diameter) are drilled through the walls of the pipe approximately every 20 cm along the length of the frame to permit water to enter the pipe and decrease frame buoyancy. The corners of the frame consist of four PVC 90° elbows affixed to the pipe with PVC primer and glue. The two halves of the frame are connected with two 15 cm long sections of 12.5 mm inside diameter Tygon tubing that fit tightly over the PVC frame ends and serve as hinges to open and close the net. Knotless nylon netting is used to minimize abrasion to captured fish; Regents, Ace, and Delta are commonly used styles of netting. The netting is comprised of two panels. The first panel is rectangular with short and long dimensions equal to the net length and frame circumference, respectively. A 9 cm wide tube/fold is sewn along the edge of one of the long sides, through which the PVC frame is inserted, preventing gaps between the frame and the net through which fish might escape. The short sides of the panel are sewn together as a seam (Figure 1)
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113 Table 1. Appropriate net mesh size for size range of various reef fishes. Family
Species
Standard length (mm)
Square mesh size in mm
Scorpaenidae Serranidae
Sebastes spp. Paralabrax clathratus
Embiotocidae
Brachyistius frenatus Embiotoca jacksoni Hexagrammos decagrammus Clepticus parrai Halichoeres pictus Halichoeres garnoti Halichoeres semicinctus Thalassoma bifasciatum Heterostichus rostratus Chromis cyanea Coryphopterus personatus Coryphopterus glaucofraenum Gnatholepis thompsoni Ocyurus chrysurus
15–100 15–100 100–250 30–120 100–250 100–250 10–30 10–30 10–100 100–250 10–30 30–350 10–60 10–30 10–70 10–70 80–120
1.5–6.0 1.5–6.0 6.0–12.0 6.0 6.0–12.0 6.0–12.0 1.5 1.5 1.5–6.0 6.0–12.0 1.5 1.5–12.0 3.0 1.5 1.5–6.0 1.5–6.0 6.0
Hexagrammidae Labridae
Clinidae Pomacentridae Gobiidae
Lutjanidae
to form the side-walls of the net. To enclose the net, a second panel of dimensions the same as the frame is sewn onto the back edge of the first panel. A heavy polyester carpet thread is used for sewing the tube and the panels of netting together.
Operation and applications The BINCKE can be operated by one or two divers depending on its size and method of collection. For the collection of large aggregations of fishes, two divers, one on either side of the BINCKE, encircle the aggregation. This is best achieved when the fish are bounded by physical structure (e.g., vertical rock wall) restricting their direction of escape. Alternatively, for quickly moving species that reside near the reef surface, one diver will hold the BINCKE open while one or more other divers herd fish towards and into the net. A single diver can hold both sides of the frame and sweep the BINCKE vertically towards the water surface or the reef bottom; this again restricts the direction of escape of fishes by using a physical barrier. Finally, the net can be laid flat and open on the reef surface and baited to attract large individuals of the target species. As fish accumulate over the net to feed, the
two halves of the frame are raised to enclose them. A closed BINCKE is easily transported by one diver back to a boat or to shore without escapement of fish; captured fish can also be transferred from the BINCKE to large plastic bags or mesh cylinders underwater to allow for more collecting before transport. Specific examples of the application of this net include the collection of several species in a variety of families from several locations:
Temperate reef fishes Juveniles Sebastes spp. (Scorpaenidae), Paralabrax clathratus (Serranidae) and Brachyistius frenatus (Embiotocidae) – Juvenile Sebastes spp. and P. clathratus (15– 100 mm standard length (SL)), and B. frenatus (30– 50 mm SL) were collected from kelp forests along the coastal northeastern Pacific. Large aggregations of juvenile Sebastes spp. above the reef were collected with a large (1 m × 2 m frame) BINCKE by two divers. Single fish and small aggregations of Sebastes spp., P. clathratus, and B. frenatus associated with large kelp plants (e.g., Macrocystis pyrifera and Laminaria spp.) were collected by one diver
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114 sweeping a smaller (0.5 m × 1.0 m frame) BINCKE along plants and upward toward the kelp surface canopy. Individuals or small aggregations near the reef were collected by a single diver sweeping the smaller BINCKE downward over the reef surface. Large juveniles and adults Brachyistius frenatus and Embiotoca jacksoni (Embiotocidae), Heterostichus rostratus (Clinidae), Hexagrammos decagrammus (Hexagrammidae), Halichoeres semicinctus (Labridae), and Paralabrax clathratus (Serranidae) – Large juvenile and small adult B. frenatus (60–120 mm SL) and H. rostratus (50–350 mm SL) were collected from kelp forests off southern California. Small to large aggregations of juveniles and solitary adults in the kelp surface canopy were collected with a 0.5 m × 1 m frame BINCKE by one diver with an upward sweeping movement initiated from 2–3 m below the canopy. Large juvenile and small adult (100– 250 mm SL) H. decagrammus, E. jacksoni, H. semicinctus, and P. clathratus were collected from the reef surface. H. decagrammus, H. semicinctus, and P. clathratus were often collected using the baited technique as described above.
Large juveniles and adults Chromis cyanea (Pomacentridae), Coryphopterus personatus, Coryphopterus glaucofraenum and Gnatholepis thompsoni (Gobiidae) – Large juvenile C. cyanea (40–70 mm SL) and juvenile and adult C. personatus (30 mm SL), C. glaucofraenum and G. thompsoni (40–70 mm SL) were collected by slowly herding fish into an open BINCKE flush with coral or a sand bottom.
Acknowledgements We thank V. Breda, G. Hoelzer, M.M. Perez, and M. Singer for contributing to the initial development and application of the BINCKE. J. Harding, M. Hixon, D. Kalik, and S. Thompson provided helpful comments in preparation of the manuscript. Support during manuscript preparation was provided to M. Carr by NSF grant OCE-92-17163, the National Undersea Research Program (Caribbean Marine Research Center), and Minerals Management Service grant 14-35-0001-30758, and T. Anderson was supported by a Friday Harbor Laboratories Postdoctoral Fellowship, University of Washington.
Coral reef fishes
References cited
Juveniles Chromis cyanea (Pomacentridae), Coryphopterus personatus (Gobiidae), Clepticus parrai, Halichoeres garnoti, Halichoeres pictus and Thalassoma bifasciatum (Labridae), and Ocyurus chrysurus (Lutjanidae) – Juvenile and adult C. cyanea (10– 60 mm SL), C. personatus (10–30 mm SL), juvenile C. parrai, H. pictus, and T. bifasciatum (10–30 mm SL), and O. chrysurus (80–120 mm SL), were collected from both coral and artificial reefs in the Bahamas or U.S. Virgin Islands. Small to large aggregations (≤ 50 fish) of all five species were collected by slowly herding fish into a BINCKE set at the edge of a coral promontory.
Anderson, T.W. 1983. Identification and development of nearshore juvenile rockfishes (genus Sebastes) in central California kelp forests. Master’s Thesis, California State University, Fresno. 216 pp. Anderson, T.W. 1994. Role of macroalgal structure in the distribution and abundance of a temperate reef fish. Mar. Ecol. Prog. Ser. 113: 279–290. Anderson, T.W. & B.D. Sabado. 1995. Correspondence between food availability and growth of a planktivorous temperate reef fish. J. Exp. Mar. Biol. Ecol. 189: 65–76. Behrents-Hartney, K. 1997. Site fidelity and homing behaviour of some kelp bed fishes. J. Fish Biol. (in press). Carr, M.H. 1989. Effects of macroalgal assemblages on the recruitment of temperate zone fishes. J. Exp. Mar. Biol. Ecol. 126: 59–76. Carr, M.H. 1991. Habitat selection and recruitment of an assemblage of temperate zone reef fishes. J. Exp. Mar. Biol. Ecol. 146: 113–137. Carr, M.H. 1994. Effects of macroalgal dynamics on recruitment of a temperate reef fish. Ecology 75: 1320–1333. Carr, M.H. & M.A. Hixon. 1995. Predation effects on early post-
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115 settlement survivorship of coral-reef fishes. Mar. Ecol. Prog. Ser. 124: 31–42. Coyer, J. & J. Witman. 1990. The underwater catalog: a guide to methods in underwater research. Shoals Marine Laboratory, Cornell University and New York Sea Grant Program, Ithaca. 72 pp.
McCleneghan, K. & J.L. Houk. 1978. A diver operated net for catching large numbers of juvenile marine fishes. Calif. Fish Game 64: 305–307. Singer, M.M. 1985. Food habits of juvenile rockfishes (Sebastes) in a central California kelp forest. U.S. Fish. Bull. 83: 531–541.
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