669

Abstract.-This study examined thecatchfrom gill nets seton nearshore Gillnetting in southern New Zealand: rocky reefs around the Kaikoura Pen­ insula on the east coast of the South duration effects of sets and Island of New Zealand. The combined catch of 114 net sets ofthree net mesh entanglement modes of fish sizes (2.5",3.5", and 4.5") was analyzed for the mode of entanglement of cap­ Michael J. H. Hickford tured fish and for duration effects on fish. Fusiform species were commonly David R. Schiel gilled and wedged, whereas laterally Department of Zoology. University of Canterbury compressed species usually became Private Bag 4800. Christchurch. New Zealand tangled byfins or spines; these patterns appeared to be a consequence of the e-mail address:Miltype of net con­ indirect proportion to thetimefished, affect the susceptibility of individual struction, the hanging coefficient, theincreasewouldhavebeen 100 per­ fish to gill nets. net saturation and characteristics cent. Thepresence ofcaptured, strug­ ofnets, such as theirvisibility, elas­ glingfish andofdeadfish mayresult ticity of meshes, and filament size. in the efficiency ofgill nets decreas­ Dimensional characteristics of ing with time (Kennedy, 1951). fishes, such as length-weight rela­ The analysis of catches of fish tionships (Kipling, 1957), length­ taken in gill nets is complicated by condition relationships (Regier, the passive nature of this type of 1969), and length-girth relation­ fishing gear (Berst and McCombie, ships (Kawamura, 1972), can also 1963). Severalfactors affect gill.net influence selectivity. catches, such as the movement of Itis generally agreed that a given fish, the shape and structure ofthe mesh size provides a size selection fish, and the associative pattern or for a particular species thatis char­ grouping of the individuals of any acterized by a lower size limit, be­ species or assemblage of species low which fish are small enough to (Moyle, 1950). pass through the mesh withouthin­ The aim ofthe present study was drance, and by an upper size limit, to analyse the size range and abun­ above which fish are too large to dance ofthe most common fish spe­ enter the mesh and become en­ cies in gill-net catches from near­ tangled (Hamley, 1975). Between shore reefs in southern New Zea­ these limits the length-frequency land. The datafor this analysis were distribution ofthe catch is approxi­ derived from the catch ofnets used Manuscript accepted 16 April 1996. mately normal, with a mode at the for comparison of reef fish popula­ Fishery Bulletin 94:669-677 (1996). length where the corresponding tions previously assessed by visual 670 Fishery Bulletin 94(4). 1996 survey (Hickford and Schiel, 1995) and from gill nets have been "gilled." Ifthe mesh encircling the body thatwere usedfor behavioral observations. By record­ was posterior to the base ofthe pectoral fin, the fish ingthe morphological features ofthe catch, along with was determined to have been "wedged." Ifa fish was the form ofentanglement, the primaIyfactors that de­ held because mesh had snagged an appendage, such termine the vulnerability ofindividual species to par­ as the fins, spines, teeth, or maxilla, or ifthe fish's ticular mesh sizes could be identified. Analysis ofthe struggling had simply enveloped it in the mesh, it quantity and quality ofthe catch landed from gill nets was described as "tangled." Careful handling of the set for various periods should yield an optimum set nets resulted in very few "drop-outs" from the net. time that will maximize landings and reduce wastage. However, any fish that were loose in the net were excluded from subsequent entanglement analysis. Entanglement data were collated for each species Materials and methods in each mesh size. Because the species composition of individual net sets was so variable and because The gillnet catch analyzed in this study was pooled many species were caught only in a small proportion from several experiments. Consequently, the result­ of sets, the analyses ofentanglement data were re­ ing sampling design is not orthogonal. The netting HLticted to the five most commonly caught spedes. was done on rocky reefs around the Kaikoura Penin­ This produced a 5x3x3 contingency table, in which sula on the east coast ofNew Zealand's South Island the number of fish caught were categorized accord­ (42°25'S, 173°42'E) from 8 January 1993 to 26 Feb­ ing to species, mesh size, and entanglement mode. ruary 1993. The nets (Table 1) were set from a 6­ This table was analyzed by using a log-linear model meterrunabout and hauledin by hand. Each netwas that required thirteen iterations for the G-value to be setin a random direction and the ends were anchored minimized. ( IaGI < 0.001; Sakal and Rohlf, 1981). The withweights andmarkedwith surface buoys. At least odacidOdaxpulluswas the only species caughtinlarge 10 meters separated any two nets. The nets were set enough numbers across most net sets for individual on the bottom at depths ranging from 3 to 15 meters statistical analysis ofentanglement to be done. and for periods of11-17 hours.At all sites thebenthic The duration ofeach net set was recorded. Two set habitattype hadbeen described (Hickford andSchiel, times were chosen for analysis: a 6-h daytime set 1995) and the fish populations had been surveyed from late morning to late afternoon and a 15-h night with visual transects by divers immediately before set from late afternoon to early morning. The num­ the nets were set. At the end ofall sets, the nets were beroffish and number ofspecies caught during each placed inbins andbrought backto the laboratory with set were compared.Acomparison ofthe capture rates fish still entangledinthemeshfor analysis ofthecatch. ofcommon species was also made between day and The combined catch of114 net sets ofthree mesh sizes night sets andbetween mesh sizes. Eachfish caught over a single known habitat type (rocky pinnacles, was given a condition index according to the degree of mixed. algae [Hickford andSchiel, 1995]) was analyzed.. damage it had sustained while in the net (Table 2). As each fish was removed from the net, its species and fork length (mm) were recorded as was the method by which each fish had become trapped in Results the mesh. If a fish was held by the mesh encircling its body between the posterior edge ofits operculum The 114 net sets caught 1,165 fish from 14 families and the base ofits pectoral fin, it was determined to (Table 3). The odacid Odax pullus (46% of the total

Table 1 Table 2 The dimensions ofthe gill nets used in fishing during this Descriptions of the indices used to categorize the condi­ study. Mesh size is given in inches by the manufacturers tion offish landed in gill nets. andismeasured as the diagonal length ofa stretched mesh. Filament size is the diameter ofthe monofilament. Condition index Damage

Net and mesh dimension Measurement No damage Chafing or scale loss from contact with gill net Net length (m) 30 30 30 Minor damage Minor lesions; fin or eye damage Net height (m) 1.80 1.75 1.72 Mejor damage Mejor lesions; flesh loss or sea lice Mesh size (inches) 2.5 3.5 4.5 damage Filament size (mm) 0.36 0.48 0.58 Severe damage Loss ofskeletal material Hickford and Schiel: Gillnetting in southern New Zealand 671

Table 3 The species, common name, fisheries code, and number offish caught in each ofthe three mesh sizes and in total. The number of individual net sets are shown in parentheses under the mesh size.

No. offish

Mesh size

Family and Common Fisheries 2.5" 3.5" 4.5" 'lbtal no. species name code (29) (30) (55) (114)

Myliobatidae Myliobatis tenuicaudatus (Hector, 1987) Eagle ray EGR 0 1 0 1 Moridae Latella rhacinus (Bloch and Schneider, 1801) Rock cod ROC 2 1 0 3 Pseudophycis bachus (Bloch and Schneider, 1801) Red cod RCO 2 4 1 7 Carangidae Pseudocaranx dentex (Bloch and Schneider, 1801) Trevally TRE 0 0 1 1 Trachurus declilJis (Jenyns, 1841) Jack mackerel JMA 1 1 2 4 Arripidae Arripis trutta (Bloch and Schneider, 1801) Kahawai KAH 88 6 13 107 Aplodactylidae Aplodactylus arctidens Richardson, 1839 Marblefish GTR 56 45 19 120 Cheilodactylidae Cheilodactylus spectabilis (Hutton, 1872) Redmoki RMO 0 0 5 5 Nemadactylus macropterus (Bloch and Schneider, 1801) Tarakihi TAR 0 1 0 1 Latrididae Latridopsis ciliaris (Bloch and Schneider, 1801) Blue moki MOK 115 40 29 184 Latridopsis forsteri (Castelnau, 1872) Coppermoki CMO 0 4 2 6 Latris lineata (Bloch and Schneider, 1801) Trumpeter TRU 2 0 0 2 Mendosoma lineatum Guichenot, 1849 Telescope fish TEL 1 0 0 1 Mugilidae Aldrichetta forsteri (Cuvier and Valenciennes, 1846) Yellow-eyed mullet YEM 22 1 0 23 Labridae Notolabrus celidotus (Bloch and Schneider, 1801) Spotty STY 7 0 0 7 Notolabrus fucicola (Richardson, 1840) Banded wrasse BPF 46 7 5 58 Pseudolabrus miles (Bloch and Schneider, 1801) Scarlet wrasse SPF 2 2 0 4 Odacidae Odaxpullus (Bloch and Schneider, 1801) Butterfish BUT 462 72 7 541 Pinguipedidae Parapercis colias (Bloch and Schneider, 1801) Blue cod BCO 6 3 1 10 Gempylidae Thyrsites atun (Euphrasen, 1791) Barracouta BAR 0 1 0 1 Istiophoridae Seriolella brama (Gunther, 1860> Blue warehou WAR 45 31 1 77 Monacanthidae Parika scaber

'lbtal 857 220 88 1,165

catch), the latrid Latridopsis ciliaris (16%), and the these fish were caught in the larger mesh sizes, and aplodactylid Aplodactylus arctidens (10%) repre­ few were caught by wedging and tangling (Table 4). sented most ofthe total catch. Forthe five most com­ In contrast, the large, slow-moving latrid L. ciliaris monly caught species, the degree of association be­ was mostly tangled in the 2.5" mesh, gilled and tween mesh size and method ofcapture differed for tangled in approximately equal numbers in the 3.5" different species (G=81.395, X20.05[161=26.296, mesh, and mostly gilled in the 4.5" mesh. Odaxpullus P

Table 4 Observed catch frequencies by mode ofentanglement for five commonly caught species.

Observed catch

Species Mesh (inches) Gilled Wedged Tangled Thtal

NotolabruB fucicola 2.5 39 4 1 44 3.5 4 1 1 6 4.5 2 1 1 4 Total 45 6 3 54

Oda:c puliUB 2.5 317 74 41 432 3.5 35 25 3 63 4.5 2 1 1 4 Total 354 100 45 499

AplodactylUB arctidens 2.5 18 5 28 51 3.5 24 14 4 42 4.5 5 10 2 17 Total 47 29 34 110

ArripiB trutta 2.5 61 13 9 83 3.5 1 1 3 5 4.5 4 1 3 8 Total 66 15 15 96

LatridopBiB ciliariB 2.5 18 11 60 89 3.5 15 1 19 35 4.5 16 5 3 24 Total 49 17 82 148

ingA. arctidens was mostly tangled in the 2.5" mesh, for analysis. Gilled fish were significantly largerthan but most fish were gilled and wedged in the 3.5" and wedged fish (F1104=35.77, P<0.001) in both the 2.5" 4.5" mesh sizes. The pelagicArripis trutta was mostly and 3.5" nets. In the 2.5" mesh, tangled fish were gilled in the 2.5" nets, but the number offish gilled significantly larger than gilled fish (F2,453=78.41, and tangled was approximately equal inthe 3.5" and P<0.001). Overall, the 3.5" mesh caughtsignificantly 4.5" nets. larger fish than did the 2.5" mesh (F1,104=453.36, Overall, the mean fork length of each species in­ P

600 A A _Gilled 500 3 9 3' 69 '37 69 44 '3 17 '0 5 E1Wedged 100% I!ITangled 400 60% ;: 60% \!! lil 200 40%

20% '00

coo co o coo 00 0% ~ ~ g g .. ..N 0 ... l- a: :J:: 0 ... a: -' ::> a: :; m m m '" 0- I- 0- W "I U i ~ ~ 0 :; ~ ~ l- a: w III III il U Cl :;" a: rn I- ~ >- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

B '8 12 12 600 B '00% w Ul 500 80% + E 60% .§. 400 .5 40% 0 <: 300 :!! N j!'" ~. i! 20% .e 200 <: 0% Z g .. ll: m m ~ :::ii 100 "I ~ ~ ~ ~ ~ ~ ~ ~ 000 00000000 0 ... I- 0 0 ... a: -' ::> :; 0- ::> 0 0- ~ w Maximum girth (mm) III III ::Ii ~ ~ " ::Ii rn rn ~ I- w lil U !5 :; a: I!: I >- -Wedge. DGllled CTangled I

600 C Figure 2 500 Proportion ofbutterfish, Odaxpullus. caught by

N- each entanglement mode in the IAl 2.5" mesh 400 "'5!N t:: and (B) 3.5" mesh. n = the number offish in each 300 size class.

200

'00

000 000 000 000 000 000 000 Discussion

Species Each species showed a distinctive pattern in its form Figure 1 ofentanglement in the three mesh sizes. These pat­ The mean fork length (+1 SE) offish captured by each en­ terns appear to be a consequence of the behavioral tanglement mode in the IA) 2.5" mesh, (BI 3.5" mesh, and and morphological characteristics unique to each Ie) 4.5" mesh. n = the number of fish from each species species. For example, Arripis trutta were caught caught in each method. See Table 3 for species codes. mainly by being gilled in the nets. This species is a pelagic carnivore that is dependenton a strongswim­ mingthrust for catching prey. Once gilled, they would or the two set durations in the number of Aplo­ be expected to drive forward firmly into the net and dactylus arctidens, Latridopsisciliaris, orArripis trutta to become wedged. The low number of wedged fish caught per hour (all F values were not significant>. for this species may be a result of their firm flesh, The proportion ofdamaged fish in the landed catch which is not easily compressed by the mesh and was small for nets of all three mesh sizes set for six which may prevent them from entering the net fur­ hours butincreased markedly for the longer settimes ther. Larger fish, despite their greater swimming (Fig. 5). ANOVA ofthe condition index of 16 fish se­ thrust (Lander, 1969), cannot enter the small mesh lected randomly from each mesh size and each set sizes far enough to become wedged. time showed that fish were significantly more dam­ Odax pullus were mostly gilled and wedged in the aged in the longer sets (F190=19.23, P

40 A B 35 3.5 0.6 :E 30 '":::l Af--+ 30 0.5 rl 25 .c 2.5 0.4 .. 20 '"0 2.0 15 0.3 11 1.5 E 10 0.2 :::l 1.0 Z t:- 0.5 0.1 0 -1 0.0 0.0 6 15 2.5" 35" 4.5" 2.5' 3.5" 4.5' 5 .2 8- c D 0.8 4.0 fi.:::l 10 rI 0.7 3.5 B ~25.Mesh .c :E I I I £ 0.6 3.0 0 U•• l lIt.u r..., 1_3.5 Mm I 0.4 2.0 'il -+-4.5· Mesh ., 0.3 1.5 Q... 0 0.2 1.0 11 0.1 0.5 E ~ :::l 0.0 0.0 Z 2.5' 3.5" 4.5" 25" 3.5" 4.5'

15 Mesh size Set time (hours) Figure 4 Figure 3 The mean number offish caught per hour (+1 SE) for four The mean number of fish (A) (±1 SE) and the common species in three mesh sizes and in two set mean number of species (B) (±1 SE) landed by durations. the three mesh sizes against time.

2.5" Mesh 3.5" Mesh 4.5" Mesh 100 the mesh. However, several other characteristics .c jl 711 83 175 28 89 16 .. 80 oHane unique to O. pullus make this species very vulner­ £I Minor 0" 80 able to capture by gill nets. The fusiform body shape ., mMajor ..'" 40 • severe ofthis species allows even large individuals to enter 1: .,~ 20 the mesh ofa gill net to about halftheir body length 0- before further forward movement is prevented. Their 15 15 15 sinuous swimming motion and weak pectorals do not Set time (hours) allow them to swim backwards out of a gill net or to stop quickly. This, coupled with the tendency of O. Figure 5 pullus to swim below the algal canopy where they The percentage composition of the catch from nets of three mesh sizes in terms ofcondition of are likely to have difficulty detecting the mesh, fish after various set times. n = the number of makes this species one ofthe most vulnerable to gill fish landed by each mesh size after each set du­ nets. ration. See Table 2 for damage categories. Aplodactylus arctidens were mostly gilled and tangled when caught in the nets. This mode ofcap­ ture may be due to the strong dorsal spines in this species' anterior dorsal fin which prevent the mesh Notolabrus fucicola, a labrid species, were mostly from passing further along the fish's body. The dif­ gilled when caught in the nets. This is likely to be a ferences between mesh sizes in the proportions ofA. result of their labriform swimming motion, which arctidens caught by each method may be a result of enables them to swim backwards outofthe net rather mesh selectivity. The great number of fish tangled than having to force their way through the mesh. If in the 2.5" mesh is probably a result oflarger fish be­ a labrid's backward motion is not prevented by its coming tangled by their fins and spines. Small fish gills becoming snagged, it invariably escapes from caught initially in equivalent numbers in the larger the mesh. Labrids have also been observed to dis­ mesh sizes are able to pass throughthenetunhindered. play a unique rolling motion when first tangled in Hickford and Schiel: Gillnetting in southern New Zealand 675 the net (Hickford and Schiel, 1995), a motion that relatively few studies directed at exploring the often results in a fish freeing itselffrom the net. mechanisms that limit the catch. Our study shows The deep-bodied Latridopsis ciliaris were mostly evidence ofa set-time saturation effect with all three tangled and gilled. The small number ofthis species mesh sizes. Neither the number of fish caught nor that were found wedged in net mesh is probably due the number ofspecies caught were significantly dif­ to none of the mesh sizes being large enough to al­ ferent between the six and fifteen hour sets. How­ low larger blue moki to enter the nets any further ever, these different set times had only a small over­ than their gills. The significantly greater number of lap diurnally and saturation may have been influ­ fish tangled in the 2.5" mesh is a result oflarger fish enced by differing periods offish activity. There was becoming tangled by their large fins and protruding no evidence in either the gill nets or in both under­ fin rays. Large, laterally compressed fish, such as L. water observations and videos (Hickford and Schiel, ciliaris and Nemadactylus macropterus, are not unpubl. data). that predators affected catches. strong swimmers (Doak, 1991). They rely on muscu­ Space limitation in the gill net itself is regarded lar undulations from head to tail in order to swim, as a major component ofthe saturation effect. Once and they brake with their pectoral fins. This weak a fish has been captured, the particular cell that it swimmingability, coupled with their large spiny fins, occupies and the cells immediately surrounding it resulted in L. ciliaris often becoming entangled by a are not capable of catching other fish. Koike and single fin rather than being truly enmeshed in the Takeuchi (1982) examined this feature and found net. that fish were repulsed around a capturedindividual Winters and Wheeler (1990) stated that the differ­ for some but not all mesh sizes. Kennedy (1951) cited ence in fishing power between nets ofvarious mesh additional ways in which the efficiency of a gill net sizes may be a result ofdifferences in the proportion decreases with time. These included the presence of of fish caught by each entanglement mode in each captured, strugglingfish (which makes the net more mesh size. They stated that the three modes ofcap­ obvious and could frighten other fish away) and the ture have differentfishing powers thatmayvarywith presence ofdead fish (which may cause other fish to mesh size, but in general, wedging is more effective avoid the area). Kennedy speculated thatthe greater than gilling, and both these modes are much more the catch during the initial time period, the greater effective than tangling. However, the results ofour the difference between the initial (observed) and fi­ study show that for total fish numbers caught in all nal (expected) catches. mesh sizes combined, most fish were gilled (60%), The effect ofset time on total and species catches whereas wedged (17%) and tangled (23%) fish made in gill nets has a direct bearing on the use of this up significantly lower proportions ofthe catch. This gear in assessing the abundance and species diver­ result suggests that, in the case ofour study, gill nets sity of fish populations. Some studies have focused do infact "gill" fish rather than capture them by tan­ on comparing multi- to one-night catches (Richards gling or wedging. and Schnute, 1986; Minns and Hurley, 1988).The Mesh-size selectivity was evident from the mean evidence presented here, however, suggests that net length offish captured by each method in each mesh saturation can occur during a single night, although size. Although the fork length of gilled and wedged this may be confounded by the varying behaviors of fish increased with increasing mesh size, the fork the fish species present. length of tangled fish was less uniform in its rela­ The apparent similarity in catch rates of Odax tionship with mesh size. pullus, Arripis trutta, Aplodactylus arctidens, and The results ofour study show that tangling is not Latridopsis ciliaris during day and night sets was the result solely of size selection and is not consis­ unexpected. These species are more active duringthe tent across mesh sizes. The proportions of Odax day and would be expected to be caught in signifi­ pullus caught by each method, when plotted against cantly greater numbers in the day sets. Greater av­ fork length, show a clear transition as fork length erage numbers ofthese species were caught during increases from most fish being wedged to the major­ the daytime, but the catches were so variable that ity being tangled. This transition would not occur if any patterns may have been masked. the size of tangled fish were independent of mesh The condition offish in the landed catch is closely size, because fish of all sizes would then become related to the length of time a net is in the water. tangled in any given mesh size. The catch of nets set for longer than six hours will Although the concept of gill net "saturation," or contain a high proportion ofdamaged fish. The rela­ diminishing returns with increasingeffort, is gener­ tion between set time and condition is confounded ally recognized as a limiting factor in catch per unit by the fact that nets set for periods longer than six of time (Minns and Hurley, 1988), there have been hours were usually left in the water overnight. Dur- 676 Fishery Bulletin 94(4). J996 ingthe hours ofdarkness, lobsters (Jasus edwardsii) fully acknowledge the financial support ofthe World feed more actively (Gunson, 1983) and can severely Wide Fundfor Nature (New Zealand), through spon­ damage fish. However, lobsters often become tangled sorship from the Thranga Trust, andthe New Zealand in nets while feeding on dead or dying fish in the Lotteries Fund for Scientific Research. Comments by bottom region ofthe nets and were frequently caught three anonymous reviewers were helpful in the devel­ during nighttime sets in this study. Most intertidal opment ofthis manuscript. and subtidal marine isopods also peakintheir activ­ ity rates during the hours of darkness (Jones and Naylor, 1970; Fincham, 1973). Sealice cancompletely Literature cited devour all but the skin and calcified structures of a fish. The fact thatboth these predatorsfeed predomi­ Berst, A. H. nantly at night means that damage incurred by fish 1981. Selectivity and efficiency ofexperimental gill nets in South Bay and Georgian Bay ofLake Huron. Trans. Am. would be greater for overnight sets. Fish. Soc. 90:413-418. Inourstudy, few fish were damaged in the six hour Berst, A. B., andA. M. McCombie. sets, but up to 40% offish were damaged in the fif­ 1963. The spatial distribution offish in gill-nets. J. Fish. teen hour sets. Therefore, any increase in the num­ P..es. Buard Can. 20:735-742. ber offish caught beyond six hours may be offset by Boy, v., andA. J. Crivelli. 1988. Simultaneous determination ofgillnet selectivity and more fish being severely damaged. population age-class distribution for two Cyprinids. Fish. Gill nets do not representatively sample the fish Res. 6:337-345. population at reef sites; none of the species in this Doak, W. study was caught in its proportional occurrence in 1991. Wade Doak's world ofNew Zealand fishes. Hodder nearshore habitats (Hickford and Schiel, 1995). Be­ and Stoughton Ltd, Auckland, 223 p. Fincham, A. A. havioral traits, such as swimming motion, and mor­ 1973. Rhythmic swimming behaviour ofthe New Zealand phological characteristics, such as spines or large sand beach isopod Pseudaega punctata Thomson. J. Exp. fins, act to make some species more vulnerable than Mar. BioI. Ecoi. 11:229-237. others to the fishing action ofgill nets. The 2.5" mesh Garrod, D. J. is clearly the most effective at catching most species 1961. The selection characteristics of nylon gill nets for Tilapia esculenta Graham. J. Cons. Int. Explor. Mer offish and is particularly effective at capturing ju­ 26:191-203. venile and resident reeffish. Nets ofthis small mesh Gunson,D. size are commonly available to amateur fishermen 1983. Collins guide to the New Zealand seashore. William in New Zealand, who use them in nearshore waters. Collins PubI., Ltd., Auckland, 240 p. Our studyclearlyshows that although commercially Hamley, J. M. 1975. Review ofgillnet selectivity. J. Fish. Res. Board Can. valuable species, such as Odax pullus, Latridopsis 32:1943-1969. ciliaris, and Arripis trutta, can be caught in great Bickford, M. J. B., and D. R. Schiel. numbers around coastal reefs, the bycatch of resi­ 1995. Catch vs count: effects ofgill-nettingonreeffish popu­ dent species, such as Aplodactylus arctidens, lations in southern New Zealand. J. Exp. Mar. Bio. Ecoi. Notolabrus fucicola, and a broad range ofothers, is 188:215-232. Jones, D. A., and E. Naylor. considerable. Most of these species are of no com­ 1970. The swimming rhythm of the sand beach isopod mercial value, but their removal from nearshore Eurydice pulchra. J. Exp. Mar. BioI. Ecoi. 4:188-199. waters may well have long-term consequences on Kawamura, G. resident fish populations in areas where consider­ 1972. Gill-net selectivity curve developed from length-girth able gill nettingoccurs, such as aroundthe Kaikoura relationship. Bull. Jpn. Soc. Sci. Fish. 38:1119-1127. Kennedy, W. A. Peninsula. 1951. The relationship of fishing effort by gill nets to the interval between lifts. J. Fish. Res. Board Can. 8:264­ 274. Acknowledgments Kipling, C. 1967. The effect of gill-net selection on the estimation of weight-length relationships. J. Cons. Int. Explor. Mer We thank S. Nicholls, M. Davidson, A. Scott, C. 23:51-63. Clarke and G. Carbines for assistance with field Koike, A., and S. Takeuchi. work. Logistic support was provided by the Univer­ 1982. Saturation of gill-net for pondsmelt, HypomeBuB sity ofCanterbury's Edward Percival Field Station, transpacificus nipponensis. Bull. Jpn. Soc. Sci. Fish. and we are grateful to J. van Berkel for his assis­ 48:1711-1716. Lander, R. H. tance atall stages ofourexperiment. J. B. Jones and 1969. Swimming thrust ofsockeye salmon (Oncorhynchus the Ministry ofAgriculture and Fisheries provided nerka) in relation to selectivity of gillnets. J. Fish. Res. equipment, logistic support, and expertise. We grate- Board Can. 26:1383-1385. Hickford and Schiel: Gillnetting in southern New Zealand 677

McCombie, A. M., and A. B. Berst. Richards, L. J., and J. T. Schnute. 1969. Some effects ofshape and structure offish on selec­ 1986. An experimental and statistical approach to the ques­ tivityofgill-nets. J. Fish. Res. Board Can. 26:2681-2689. tion: isCPUE anindex ofabundance? Can. J. Fish.Aquat. McCombie, A. M., and F. E. J. Fry. Sci. 43:1214-1227. 1960. Selectivity ofgill nets for lake whitefish, Coregonus Sokal, R. R., and F. J. Rohlf. clupeaformis. Trans. Am. Fish. Soc. 89:176-184. 1981. Biometry: the principles an practice of statistics in Minns, C. K., and D. A. Burley. biological research, 2nd ed. W. H. Freeman & Co., New 1988. Effects ofnet lengths and set time on fish catches in York, 859 p. gill nets. N. Am. J. Fish. Manage. 8:216-223. Van Oosten, J. Moyle,J. B. 1935. Logically justified deductions concerning the Great 19110. Gill nets for sampling fish populations in Minnesota Lakes fisheries exploited by scientific research. Trans. waters. Trans. Am. Fish. Soc. 79:195-204. Am. Fish. Soc. 65:71-75. Paulin, C. D., A. L. Stewart, C. D. Roberts, and Winters, G. B., and J. P. Wheeler. P. J. McMillan. 1990. Direct and indirect estimation of gillnet selection 1989. New Zealand fish: a complete guide. Government curves of Atlantic herring (Clupea harengus). Can. J. Printing Office, Wellington, 279 p. Fish. Aquat. Sci. 47:460-470. Regier, B. A. 1969. Fish size parameters useful in estimating gill-net selectivity. Prog. Fish-Cult. 31:57-59.