MFR PAPER 1095 Paul Struhsa ker and Donald C. Aasted are on the staff of the Southwest Fis heries Cen­ te r, National Marine Fisheries Deepwater Shri mp Trapping in Service, NOAA, Honolulu, HI the Hawaiian Islands 96812. moderate numbers with th e trawls PAUL STRUHSAKER and DONALD C. AASTED between 150 and 400 fathoms (275 and 730 m). However. the initial in­ ABSTRACT-The results of preliminary deepwater shrimp trapping sur­ vestigations indicated that trappi ng. veys in the Ha waiian Islands consisting of 82 sets involving totals of 306 rather than trawling. was perhaps a traps and 3,960 h of fishing time in the 75 to 450-fathom ( 135-825 m) more effecti ve method for capturing depth range are discussed. A variety of traps, bait containers, and baits th ese latter species. were tested. Attempts to capture the penaeid shrimp, Penaeus marginatus, larke (1972) conducted trappIng in substantial numbers were unsuccessful. More success was experienced urveys during 1969 and 1970 at sev­ in trapping the caridean shrimps Heterocarpus ensifer and H. laevigatus. era l locales off the Hawaiian island of For these species, it was found that traps covered with burlap cloth out­ Oahu. The sampling gear consi ted of fished uncovered traps by factors of 2.5 to 10. H. ensifer was found to be everal trap type . but all were un­ most abundant in depths of 200-250 fathoms (365-455 m) where catches covered traps constructed of 0.5-inch with optimum trap and bait combinations ranged from 15 to 63 pounds (6.8 ( 13-mm) mesh wire screens. This wo rk to 28.6 kg) per trap for sets of less than 24 h duration. Seventy traps set provided data on the biology and overnIght during spring 1973 off the south coast of Oahu produced a total depth distributIon of H . en.liji-r a nd of 1,015 pounds (460 kg) for an average of 14 .5 pounds (6.6 kg) per trap. H . l{/ e\'i~(/llI\ and indicated tha t H . The larger H. laevigatus was found to be most abundant in depths of ensiler mi ght be present in sufficient 240-375 fathoms (440-685 mY , where catches ranged up to 34 .8 pounds quantities to support a commercial (15.8 kg) for 4 traps. It is speculated that the various species of Heterocar­ fishery. pus represent an unexploited world resource of considerable magnitude. Further trapping trial were inter­ mittently conducted by M FS during amenable to harvest by shrimp trawls 197 1-73 at various localities in the INTRODUCTION in depths of 60-125 fathoms ( 110- H awaiian Islands. These trials were During 1967 and 1968 the National 230 m)1 (Yoshida. 1972: Struhsaker. of a preliminary nature. and various Marine FIsheries Service (NMFS) de­ Yoshida. and Shomura2 ). Two species combinations of trap. bait containers. voted four cruises of the RY Town­ of caridean shrimps. H elerocllrp1l1 a nd baits were utilized . Most of the send Crolll\\ ell to demersal resource el/liji-r Milne-Edwards and H . lael'igll­ data were obtained during fall 1972 surveys in the Hawaiian Islands. The IllS Bate (Fig. I), were a lso taken in and it became apparent at this time primary ampling gear utili zed were that burlap-covered traps were more shrimp trawls. although a few shrimp effective in capturing H . ensiler than trap stations were effected. These sur­ .~ Metric eq uivalents are approxim ate. were uncovered traps. Attempts to - Struhsaker. P., H.O. YoshIda. and R.S. veys demonstrated that the penaeid Shomura. Exploratory shrimp trawling in th e trap P . lIlarginllllls in sub tantial num­ shrimp. PenllellS IIllIrginallis Randall. H awaii an Islands. unpubl. ms .. Southwest Fisheri es Center. Honolulu Laboratory. ber were unsuccessful. Fol low-up was available in modest amounts and Honolulu. HI 96812. cruises with more extensive trapping FIgure 1.-A tr8lh specimen ot Heterocarpus ensi'er (A, lelt) about 115 mm total length . Note ocellus on the sIde ot the cephatothorax ("head" ) and the strong backwar dly projecting spines on the th ird and fourth segments of the abdomen ( " tall" ) . A tresh specimen ot Heterocarpus laevlgatus (right, B) about 175 mm total length. 24 pandalld "hnmr" In the \ I~IOII\ 01 trar\ ("- ..:""I..:r. Illhlll ( o ll ap\lbl..: n.lund \hnmp Ir..lr' (/lg 4) were aha te,ted to a Ilmll..:d dcgru.: Th e~ are 14 Inch..:, (3(-, cml high . 24 In che (60 cml In diameter al th..: I\lp. 34 In c h c~ (X6 cm) In diam..:t..:r at the bott om and ha,e \hallcl\.\ tunn..:l" l..:..Id­ in g to four entrance" The \I...:h­ bi ng con~i.,t, of I 25 -Inch (~I - mm l stretc hed mc.,h n~ Ion . Finall y. an expenmental collap"l­ bk "tent trap" (Figs. 5. 6. and 7) wa, teskJ on one occasion. Each 01 the three frame mal.. ing up the hottom. side. a nd li d of the trap mea~ure, 2X4 feet (60x 120 cm) and I" en­ cia ed with 0.5-i nch wire mesh "creen . The three frame are joined with ~pllt Figure 2.- A covered square trap. This trap type links of a size th at permit folding of F,gure 4 - A coil pllble I hrlmp p OI produced the best catches 01 H ele,oca,pus th e frames and are covered with a ensifer. "..:1\ ,If 12-1 4 h Th si ngle piece of burlap. A bridle attach­ were ,u'r"nded n"ar t h~ tri als scheduled fo r 1973 we re ca n­ ed to the corners of the lid runs trar cell ed . through the outside corners of the E-ach trap ba I bottom frame (Fig . 6) . When clo\ed. GEAR AND SAMPLING EFFORT bndle of () 2"-II1c.h th e li d is secured with a rubber strap Gear a nd S-hooks. The triangu lar end T he "squa re tra p" (in reference to frames a re attached to the bottom of its squa re cros -secti on) produced th e the trap by split links a nd have two half- lin ks welded on the leg articulat­ best catches of H elerocar p lis. It mea­ sures 2X2X 4 feet (60x60x 120 in g with the side frame (Fig 7) . The tunnels are constructed With 1.5-lnch cm) (Fi g. 21. The frame is constructed of the trap 1,lndl n (38-mm) mesh ( tretched) n)- Ion web­ of ~8- in c h ( IO- mm) di ameter steel ,et It \\a, al 0 th ba r a nd i encl osed with 0.5-in ch bi ng and are secured to entrance n ngs 3 inches (75 mm) in diameter T he squa re mes h galvani zed wire screen . out through the t: tunnels are held in place by a rubber The sides. top. a nd botto m are th en Ing bad, 1 he rrlJ strap and S-hook (Fig. 6) . covered with burlap. The tunnels (one center f,lr dtt dc.h Several bai t containers were teoted at each end) are also constructed with Itne fh c ground the screen (but are uncovered ) and Containers constructed of O.5-lnch taper to approximately 3-in ch (75 -mm) mes h screen measuri ng about 4 X 4 X 6 di a meter openings about one-third th e inc hes (lOX lOX 15 cm) were gen­ di sta nce in from each end Covered erall) superior to plastiC containers and uncovered traps of si mil a r con­ of the ame size perforated With 025- struction . but enclosed wi th I-i nc h inch (6-mm) holes or bait wrapped In (25 -mm) (bar-to-ba r) he:\.agonal wire cheese cloth . F rom I to 2 pounds creeni ng were also tested . (0.5-1 kg) of bait were ~ufticlent for " Flat traps" (Fig. 3). can tructed ~imil a r l y to the qua re traps. but mea- uring I X 2 X 4 fee t (30X60X 120 cm). we re utilized Ill OS t oft en in the shal lower depth sun eyed . It was fe lt th at the lowe r ramp angles of the tun­ nel m igh t pro\ e to be more effeclI \ e in capturing P. IIwrgill<lllll. apti\ e s pecim e n ~ of P. IIl<1r~ill<lf1l1 held In large tan I.. as ho re tend d to maintain c1o ' e contact \\ ith the bottom a nd u ' ualJ\ did not undergo e\.pl orato l1 \\ immtng heha\ lor off the bottom such a' h a ~ heen ob e n ed fo r las l.. an Flgur. 3.-A" unc:o....red a'trap 15 on the order of 50-150 fathoms (90- longl i ne floats or a more elaborate northern MaUl , and th e west coast of 275 m) greater than the depth of water buoy consisting of an I H- foot (5-m) the 1\land of Hawaii off Kawaih ae. being fis hed. A chain weight is fl ag and li ght stafl o f 2.5-ln ch (64-mm) Dunng spnng 197\, 21 set~ were snapped onto the buoy line about di ameter condUit piping which fits made oil the south coast of Oahu With 25-50 fathoms (45-90 m) below the into a weighted fr ame which 1\ fl oated our gear by personnel of the Hawaii end of the last section to a sure that with a large Inn er tube.