MFR PAPER 1310 the lowest cost, that catches and retains the greatest amount of legal-sized in good condition. The design parameters are interrelated with the overall economics of the opera­ Trap Design and Ghost tion as well ea with each other. This Fishing: Discussion section will focus on the various design factors in order to predict which way trap design may go. Size RONALD JOEL SMOLOWITZ The size of the pot is usually dictated by handling problems, deck space, and expected catch rate. In the inshore , where the availability of legal­ ABSTRACT-This paper presents an assessment of ghost fishing in the New sized lobsters is low and the boats are England fishery by reviewing trends in trap design, loss rates, lost-trap small, the pots are small. A lobsterman catch rates, and related factors. Preventative solutions are discussed. who hauls his pots every other day in­ stead of daily might use a slightly larger The studies presented in this issue of were about 72,000 pots being fished by pot if he expects a larger catch. Marine Review (40:5-6) are ISO vessels. Roughly two-thirds of In the offshore fishery the pots are ultimately concerned with developing these pots were of wood-frame con­ larger due to the larger vessels, longer preventive measures to avoid a ghost­ struction, the remaining third were all soak periods, and higher availability of fishing problem. In researching pre­ metal with nylon heads (NMFS, un­ legal-sized lobsters. ventive measures, information has been pub!. data'). The loss rate offshore has Both inshore and offshore, larger obtained which enables us to make a varied considerably from year to year pots are claimed by many fishermen to preliminary assessment of the ghost­ and vessel to vessel. Annual loss rates catch more lobsters. This may occur fishing situation as it exists today and of 100 percent were common in 1971­ because lobsters have a more difficult what may occur in the future. This dis­ 72 but decreased to 20-30 percent by time finding their way out of the pot due cussion presents this assessment and 1974. Based on confidential informa­ to the increased area to be searched. reviews preventive measures. tion gathered from logbooks and other Another reason may be a lobster­ sources, there may be as many as NUMBER OF POTS LOST density limitation, which we will cover 40,000 all-metal pots lost on the later on in this discussion. By 1973, the number of lobster offshore grounds since 1971. Approx­ The deck space limiting factor of imately 180,000 wood-frame pots were (Homarus americanus ) pots being large pots can be dealt with by using fished along the Atlantic seacoast ex­ lost offshore during the same period. collapsible or stackable pots (Munro, ceeded 2 million. The annual inshore Offshore losses are mostly caused by 1973). loss rate is claimed by many fishermen vessel propellers, dragged gear, gear to be between 20 and 30 percent; one mechanical failure, and storms. Ex­ Shape published estimate is 33 percent (Prud­ perience gained by fishermen has cut The shape of the pot is important in den, 1962:43). Most of these pots are these losses to where, in many cases, determining its resistance to storm all wood or wood framed and were ef­ they are equal to inshore loss rates. damage. Improper shape can cause pots fective fishing units when lost. Loss rates, both inshore and to turn over and roll along the ocean There are many reasons why pots are offshore, will probably remain in the bottom when subject to wave action. lost in the inshore fishery. Gear failure 20-30 percent range. However, the Prudden (1962:44) makes the following includes the pot warp parting, the buoy number of pots in both fisheries is in­ suggestions to reduce pot losses: I) Any separating from the pot warp, and the creasing, thus the absolute number of reduction in the height of a pot from the buoy breaking up. This gear failure c~n pots lost will probably increase also. present 18 inches would reduce the be caused by normal wear and tear, POT TYPE leverage tending to overturn a pot; and powerboat propellers, pot "wars" 2) The construction of a pot with in­ among lobstermen, sea gulls chewing Pot type, as speci fied by design and clined sides like a pyramid would up buoys, biting the warp, and materials, is one ofthe key indicators of change the side pressure ofa wave from many other causes. Losses are also whether a ghost-fishing situation will an overturning effect into a force press­ caused by operational mistakes such as be created. The pot-design problem, as ing the pot down on the ocean floor. setting too deep and improper ballast­ defined by history, can be simply stated Proper settling of the pot on the bot- ing. Storm surge can cause the pot to as: To build the most durable pot, for tom is also a function of shape. Drag roll on the bottom, wrapping up its Ronald Joel Smolowitz is with the buoy line, and becoming unrecovera­ 'Interview sheets on file at the Woods Hole Laboratory. Nonheasl Fisheries Center. National Northeast Fisheries Center, National ble. Marine Fisheries Service. NOAA. Woods Hole. Marine Fisheries SerVice, NOAA, In the offshore fishery in 1976, there MA 02543 Woods Hole, MA 02543.

May-JI/Ile' 1978 59 forces acting on the pot as it settles through the water column determine how the pot is going to land. Stability, a function of weight and shape, deter­ rrtines how the pot will remain on the bottom (Burgess, 1969). Ifthe pot does not assume the correct position on the bottom, the entrance heads can become obstructed or ineffective (Fig. I). Pot shape also determines what shape the heads will take. The reason that most pots are high and long as they are is to allow for a more effective head design. Head Design As the catch rates fell in the inshore fishery, the soak periods increased in order to maintain an economically via­ Figure I.-Lobster escaping from an offshore trap that landed upside down. ble catch. The 15-rrtinute soaks of hoop nets gave way to the full-day soaks of the single-compartment pot. The parlor areas but there is still quite a bit of vide better footing than nylon netting pot became necessary when soaks ex­ controversy as to their effectiveness. (Prudden, 1962:41). 2 ceeded I day. Spurr , after comparison fishing five The way the entrance head is at­ The key problem with longer soak different types of pots, believes that the tached to the bottom of the pot may also times is how to prevent escapement principal factor affecting pot efficiency be important. Wilder3 (p. 5) found that once the lobster enters the pot. The is not pot shape but parlor-head design. wide spaces along the lower sides of the answer, for the past century, has been He believes that the parlor head should pot made it difficult for the lobster to better head design. Rathbun (1887) de­ have a long steep slope terminating in a find the head and thus enter the pot. scribes variations in head design based small opening very close to the end of on reorienting the position of the head the pot and near the top. This agrees Materials ring, e.g., the opening facing slightly with Thomas' (1959) findings that For the purposes of this discussion up instead of straight into the pot. He high-rigged heads deterred escape. Our we have grouped pots into three cate­ also describes pots with tandem heads field data con firms Spurr's and gories: wood and wood-framed, metal, made of wood laths, two types that are Thomas' observations and further and plastic. still seen today. demonstrates the degree of sensitivity Thomas (1959) has conducted parlor head design parameters have that Degradation numerous experiments to improve the affects ingress and retention. Wood borers are probably the pri­ efficiency of pots. He has shown that: I) Moody (1965), from a pot­ mary degrading force acting on wood Lobsters enter a pot more readily if the escapement experiment, obtained re­ pots. Borer damage can destroy a wood lower half of the head is lined with sults that showed 90 percent of the pot as an effective fishing unit in as little fine-mesh netting, 2) high-rigged heads lobsters caught in unbaited pots escap­ time as 4 weeks. On the other hand, a inhibit escape better, and 3) head­ ing within 3 days. In baited pots, the treated wood pot may last upwards of 2 opening size affects the number and escapement rate was 90 percent in 8 years on the bottom in areas with low size of lobsters caught, as does the days. While it is difficult to make a borer acti vity. Wood borers do not af­ fitting of nonescapement devices. He direct comparison of Moody's work fect metal or plastic pots. further states that the effects of pot vari­ with our field experiments, it seems he Corrosion affects metal fastenings on ations differ with the size and composi­ had a higher escapement rate. We wood pots, wire mesh on wood and tion of the population being fished and hypothesize that this is due to the fact metal pots, and wire mesh and struc­ other fishing conditions. that he used wood-lath parlor heads tural frames on metal pots. There are Leakey (1965) feels parlor pots are a which may be less efficient in retaining many ways to cut down the corrosion waste of space and materials. His solu­ lobsters than our nylon-twine skate­ rates, such as plastic coatings, design­ tion to the retention problem is an es­ mouthed heads. On the other hand, ing against galvanic corrosion, anodiz­ cape inhibitor that he has patented. This wood-lath heads may allow more ing aluminum, etc. Leakey (1965) re­ inhibitor, as with many similar devices lobsters into the parlor in that they pro- ports zinc-coated metal-framed pots known generally as triggers, allows the lobster to enter through the head but 'Spurr. E. 1972. Lobster research project: Final reponof3-I05-R.July I969-June 1971. Unpubl. "Wilder. D. G. 1956 Experiments to improve prevents its escape back out. Triggers manuscr.. 22 p. Fish. Div .. New Harnp~hire Fish lobster Irap~. Unpubl. manuscr. Fi~h. Res. Board have been tried or are in use in many Game Dep. Can .. BioI. Sin .. 51. Andn·w~. New Bnmswick.

60 Marini' Fisheries Rel'ie,,' lasting over 5 years and some lasting 7 Efficiency timized. The preceding discussion on years. Proper anticorrosion design can pot design and materials demonstrates There is a traditional belief among probably extend a metal pot's life the fact that pots can now be designed lobstermen that metal pots are not as that are more durable and efficient than beyond 10 years. Plastic pots do not effkient as wood pots. Some of the corrode. the ones being fished commonly today. reasons why lobsters are said to be re­ The probability of a long-term. ghost­ pelled by metal pots are: .1) Me~al wire Weight fishing situation being created will only vibrates in the water fnghtenmg the Metal pots have weight advantages increase. lobsters away, 2) lobsters do not like the far exceeding wood pots. They are feel of bare metal, 3) lobsters are sensi­ lighter out of water and heavier in wa­ LOCATION WHERE LOST tive to sharp metal edges, 4) lobsters ter. In tests conducted at the Northeast sense an electric field set up by galvalllc Biological Deterioration Fisheries Center (New England Marine action, and 5) lobsters sense chemicals Resources Information Program, 1972: Since most lobstermen use synthetic produced by galvanic action. 2), one metal and one wood pot were twine in pot construction, the main There are many variables that affect a weighed in and out of water. The wate.r­ form of biological deterioration of con­ pot's efficiency, though li.ttle is know.n logged wood pot weighed 22 pounds m cern is wood-destroying organisms. In about how or why. Very little compan­ water and 115 pounds out of water. The the lobstering areas the organisms are son fishing has been performed and wire-mesh metal pot weighed 33 usually Teredo navalis in the shallow documented. Experiments that have pounds in water and 53 pounds ~ut of depths and Xylophaga atlantica in the been done have not had ample controls water. Metal pots are thus easier to deeper part of the range. to determine if metal construction alone handle on deck and have better anchor- Teredo navalis spawns about July. affected pot efficiency. We can say that ing qualities on the bottom. . The larvae settle onto the wood traps the five objections to metal pots stated Plastic pots vary, in regard to weJg~t and can destroy a trap in less than 2 above have been overcome by proper and buoyancy, with the type of plastic months. Offshore Xylophaga atlantica construction and plastic dipping. Many used and the construction method. spawns about October and can destroy a fishermen have reported plastic coated trap just as fast. and aluminized metal pots fished well. Swrm Damage It is generally thought that most lob­ Metal pots are probably more resis­ Adaptability ster areas are subject to wood-borer ac­ tant to storm damage than wooden pots tivity, though not of the same mag­ Metal and plastic are more adaptable of the same size and shape because of nitude. In most inshore and offshore than wood in pot designs that are either their greater weight on the bottom and areas an untreated wood trap would collapsible or stackable. less surface area exposed to storm probably not make it through the forces. Handling winter. In a series of comparison-fishing ex­ Wood and wood-framed pots can Corrosion periments. Wilder (footnote 3, p. 23) take a lot more abuse in handling than reports that during a severe st~rm he Location-dependent factors that wire pots. This can be compensated for lost 14 out of 19 wood pots With the influence corrosion are temperature, by building the wire pots stronger and remaining 5 damaged almosl beyond dissolved oxygen, and current velo­ more rigid by addition of a s~ructural repair. Only lout of 19 metal pots was cities. Our trap-release study dem­ metal frame. Shipboard handlmg sys­ lost during the storm. Similar results onstrated the significant difference in tems can also be modified to be less occurred during several other storms failure rates that occurred with test abusive to the pots as they come throughout his experiments. ~etal-pot samples in different areas. Corrosion aboard. Iusses that did occur were attnbuted to rates are probably higher inshore than Wire pots have a handling advantage buoy line failures. offshore. over wood in that they offer less resIs­ Experiments by Spurr (footnote 2) tance when being hauled up through the Storm Surge provide the same results: wire-mesh water. pots moved less in current and storm Storm surge and wave action are action than wood-lath pots. Catch Condition known to destroy many pots in shallow inshore waters. Though pots without The catch suffers a signi ficant degree Costs buoy lines are less susceptible to storm of claw damage and loss in wood pots The material to build an inshore action, they too probably move on the due to claws protruding between the wood pot costs from $4 to $6. To buy a bottom in depths less than 20 m. It IS laths and being hit when hauled aboard. pot already constructed costs from $8 to generally believed by lobstermen that This problem is eliminated in wire­ $14. Inshore metal pots cost about $20. pots moved by storms tend to break up mesh metal pots. Offshore double-parlor wood pots agai nst rocks on the bottom .. cost $18 in 1972. In 1974 the cost was Summer fishing is usually m shallow Pot-Type Summary $27. Metal pots of the same design depths. As fall and winter approach, were $24 in 1972, $35 in 1974, and Researchers generally agree that pots are usually moved farther offshore close to $40 in 1977. lobster-pot design has not been op- into deeper water to follow the lobsters

May-JillIL' /978 6/ and also to reduce storm losses. Pots that were lost during the summer in the shallow water probably do not survive the winter storms on exposed coasts.

Substrate Burial Pots sometimes become buried in the substrate by the action of storms and currents. This is commonly referred to as "sanding down" or "mudding up." Sanding down is quite common, in depths shallower than 16 m, in the west coast Dungeness fishery (Hipkins, 1972:9). In this fishery a pump is car­ ried on board with a special hose ar­ rangement that can be lowered to the pot and water pressure applied to free the pot, sometimes buried to a depth of Figure 2.- partially buried in sand after several weeks on the bottom. 4 m. To what degree this problem exists in the lobster fishery is unknown. We can sufficient to perform a statistical assume that a pot only needs to be bottom water temperature changes, the analysis because we cannot isolate the buried about 15 cm in the substrate be­ lobster population migrates and the effects of temperature, fishing pres­ fore its heads become relatively ineffec­ fishermen correspondingly move their sure, and moulting from those of set­ tive. There are many areas, inshore and traps. A trap lost in a location where over days. (Our surface-hauled traps there were good catches one week may offshore, where the bottom conditions had set-over periods varying from I to of substrate and current are right for not have lobsters available to it for 13 days). weeks or months afterwards. partial burial to occur (Fig. 2). We divided set-over days into three Many factors affect catchability but Destruction by basic periods. The first is the baited probably the most important are tem­ Dragged Gear period, in which some of the initial bait perature and other seasonal variations. is still in the trap and is effective. The Offshore lobstermen set their pots Since ghost traps are on the bottom for second is the transition period, in which long periods, the lobsters available to following the migrations of lobsters the bait is recently gone and the lobsters them will have a wide range of catcha­ from the deep canyons in winter up onto caught are highly active in attempts to bility coefficients varying with time. the shallow shelf in summer. Many pots escape. The third period is the ghost­ are lost in areas that are not continu­ In summation, availability and tishing period. The limits of the transi­ catchability cannot readily be used for ously pot-fished. When the pot fisher­ tion period cannot be exactly described, men move out, the draggers move in, an assessment of ghost-fishing period but in most cases the trap probably en­ catch rates due to their variability. fishing the bottomtish in the area. These tered the ghost- fishing period by the However, during the initial baited draggers haul back many lost pots and end of the second week. period these factors can be used for quite possibly destroy many others on There may be times of increased in­ estimating the initial catch, which dur­ the bottom. Only pots in the canyons gress to the trap during the ghost­ ing our experiment was more than 50 themselves probably escape being de­ fishing period. This may be caused by percent of the overall ghost catch. stroyed by draggers. the trap self-baiting, a lobster migra­ Escapement tion, or some seasonal event. This CATCH RATES makes it very difficult to relate ghost­ In our Phase III experiment, 81 Ingress minus escapement and trap catch rate to set-over days. This is lobsters were classified as missing from mortality equals retention or, in other further compounded by the low ghost­ the ghost traps, this being 33 percent of words, the catch. Catch rate is a time fishing period catch rates, in our exper­ the known ingress. Two-thirds of this function; in trap fishing the time is iment equal to 10 percent of the number were missing by the 30th day. defined in set-over days. surface-hauled catch rate. Only six of these lobsters were recap­ tured. We conclude that the escapement Set-Over Days Availability and Catchability rate from ghost traps, after the initial Set-over days are probably very im­ Ingress is a function of availability baited and transition periods, is less portant in determining rates of trap­ and catchability. A good example of the than 30 percent. This rate decreases related injury and mortality, in addition variation in availability of lobsters to a with time. This figure is in basic agree­ to their importance in catch/effort rela­ possible ghost trap can be found in the ment with that of Sheldon and Dow tionships. Unfortunately our data is not fishing strategy used offshore. As the (1975).

"\1urille Fis"aies Rel'inl' Leger, a Boston University Marine one claw and 21 percent had missing Bait Program graduate student, conducted a and/or regenerate claws. There are a number of arti ficiaJ lob­ preliminary experiment at the North­ Our field data for all three phases ster baits on the market; they have been east Fisheries Center in 1973. Sixteen combined (surface hauled) shows 11.2 used by fishermen with varying degrees inshore lobsters (70 mm ±2 mm percent of the lobsters caught missing of success. One of the goals of the ar­ carapace) and 16 offshore lobsters (74 one or both claws. The overall inci­ ti ficial bait manufacturers is to produce mm ±2 mm) were tested in 2-m diame­ dence of lobsters with one or more a product that is long-lasting in the trap. ter circular tanks under three different types of damage is 27.6 percent. This Accomplishment of this goal would conditions. Capture time was recorded field data may not truly reflect what is improve the efficiency for for each lobster placed in the tank with: occurring in the actual fishery due to longer set-over periods. Correspond­ I) Trap and bait alone, 2) trap with bait our longer set-over periods. Our data ingly this would increase ghost- fishing and one lobster, and 3) trap and bait and does show that the number of injuries catch rates. two lobsters. During I-hour test might increase with longer set-over periods, 14 of 16 lobsters tested entered periods, increases in water tempera­ Behavior the trap with bait alone; 26 of 32 lob­ ture, increases in fishing pressure, and sters entered the trap containing bait possibly be related to moulting. More The most interesting question about and I lobster; none of 6 tested entered controlled experiments are needed to trap-related lobster behavior is why do the trap with bait and 2 lobsters. This determine the effects of each of the lobsters enter traps? We must address experiment indicated a possible density above factors. this question to fully understand trap­ limitation factor in trap behavior. Incidence of newly damaged lobsters ping efficiency and thus normal and Evidence exists that some form of during a portion of the Phase III study ghost-fishing catch rates. social behavior, other than feeding and was similar for vented and nonvented We know that lobsters primarily shelter related, is affecting catchability pots. Due to the larger number of enter traps to get food (bait). We also of lobsters. Leger's experiment seems lobsters caught in the nonvented traps, know that lobsters enter unbaited traps, to conflict with the field data, indicating more lobsters were injured than in vent­ and this is usually thought to be the need for more closely controlled ed traps. Total new damage amounted shelter-seeking behavior. In the natural experiments to validate the social be­ to 9 percent of the lobsters caught; 42 environment inshore lobsters are con­ havior hypothesis. percent had old damage. sidered sol itary. rarely sharing the same Another hypothesis is that lobsters There were 10 I instances of major shelter. Offshore, on relatively flat enter unbaited traps because they have damage to lobsters in our ghost pots, 25 featureless bottom, two or more lob­ been conditioned to do so. Every week percent occurring within the first 15 sters have been observed to share the lobstermen place millions of pounds of days and 69 percent occurring before same shelter, usually a depression in bait into the water via lobster traps. the 30th day of entrapment. Mortalities the bottom. This observation is the ex­ This may constitute the major food amounted to 24.6 percent of the total ception though. source of lobsters who thus relate feed­ ghost catch, 30 percent of the mor­ This natural solitary behavior is op­ ing with traps. Upon seeing a trap a talities having major injuries prior to posite what is observed in trapping. Our lobster enters expecting a food source. their deaths. field experiment catch data shows many Probably small (sublegal) lobsters have There is considerable evidence that instances, especially in Phase III, been repeatedly caught and disgarded the greater part of major damage to where 15 or more lobsters were found by fishermen as they became con­ lobsters is trap-related. Despite the in a trap, sometimes after 8 set-over ditioned to traps being effectively a reputation of lobsters being aggressive, days. Many of those lobsters entered feeding station. Lobsters repeatedly re­ it seems aggression-related injuries in the trap after the bait was gone. The turn to the trap as a food source, much nature may be rare. Scrivener (1971) same observation is demonstrated by as birds return to window feeders. conducted behavior experiments with our "lost" trap inventories. There is Lobsters may enter unbaited pots sim­ 700 pairs of lobsters and never once ingress to unbaited traps with large ply to "check-it-out" for food. observed damaging aggression. Writ­ numbers of others lobsters present. ing about decapods, and then his This is in an area with plenty of availa­ Injury and Mortality lobsters specifically, he states: "In­ ble shelters. frequently fighting leads to physical We assume that a lobster entering a Emmel (1905) reported that 7 to 25 damage of one individual. This may be trap with 10 other individuals already percent of lobsters caught in Rhode Is­ rarer under natural conditions for some there is aware of their presence before land were missing one or both claws. species, because many of the studies entering. Lobsters possess visual, Scarralt (1973) found incidence of claw have been done under crowded labora­ chemical, and possibly sonic means of loss from 5 to 19 percent in Canadian tory conditions. Damaging aggression communication. The lobster may be en­ waters. Other wounds ranged from I to has occurred among the lobsters in the tering for some social interaction with II percent in the lobsters sampled. small holding tanks when the divider its conspecifics. Krouse (1977) analyzed catch has been pushed over but has never To determine the effects of social data which indicated 6.5 percent of been observed in the 6-foot diameter behavior on catchability, Edward lobsters caught were missing at least observation tanks."

;War-jlll//' /97ti 63 Stein et al. 4 conclude that the lobster or weakened by injuries. It is generally NMFS port agents when a fishing ves­ is much less aggressive than previously considered that healthy hard-shelled sel returns from a trip. We surveyed the thought as long as the lobsters have lobsters of trapable sizes are not com­ 1976 interviews from Massachusetts adequate space and shelter. During monly preyed upon. The predator and Rhode Island ports; these two states their experiments, observing lobster would have to get into the trap and that account for 53,000 of the 72,000 traps behavior in seminatural habitats in limits the possibilities further. Scar­ being fished offshore. The average ves­ large aquaria, there may have been one rall's (1965) work indicates that sel fished 400 traps having 25 to 50 or two damage-inducing interactions weakened lobsters confined in traps traps per trawl. The soak times aver­ between lobsters. may be subject to predation by am­ aged 4-7 days. We have data showing that many in­ phipods. Twenty-nine vessels were listed as juries are sustained by lobsters in traps. Lobsters probably do not starve to fishing 13,040 wood traps. (Many of These injuries are mostly induced by death in traps but may be weakened these vessels fish some wire traps.) One conspeci fics in the .stress conditions and stressed by starvation. Morgulis hundred and forty-nine interviews were caused by the entrapment. There is also (1916) found that lobsters starved for conducted and a loss of 1,025 pots was evidence from many sources that on­ 56 days showed no outward signs of reported; a 7.8 percent loss rate. board handling of traps and lobsters in­ emaciation and the greatest weight loss Eleven vessels fished 4,920 all-metal duces injuries. Lobsters roughly han­ was 2.89 percent. The lobsters ab­ or plastic pots. During 40 interviews a dled, such as being dumped into sorbed water making up for the loss of loss of 121 traps was reported; a 2.4 a checker, will open their claws and bite organic and mineral matter; the weight percent loss rate. down on the first thing contacted, usu­ loss would have exceeded 34 percent These loss rates at first appear very ally another lobster. otherwise. Stewart et al. (1967) held low but this is due to the fact that many The causes of trap-related mortality starved lobsters for 140 days that suf­ vessels were only interviewed once or are harder to define. Many lobsters fered physiological changes but twice. We next grouped all vessels that probably die directly from the injulies showed no outward signs of stress or were interviewed six or more times. In sustained in the traps, i.e., they are increased cannibalism. McLeese this group there were 16 vessels, fishing cannibalized by healthier lobsters or (1956) reported that the lethal limits a total of 7,290 traps, that were inter­ bleed to death. Lobsters that moult in a established for temperature, salinity, viewed 134 times for an average of 8.3 trap probably don't stand much of a and oxygen did not change after 57 days interviews each. They lost 908 traps for chance for sUIvival. McLeese (1956) of starvation. a loss rate of 12.4 percent. From the reported that lobsters near moult are port weigh-out sheets we determined less able to withstand stress, thus they ASSESSMENT OF LOSSES that these vessels were averaging 20 may also be subject to mortality in the In this section we will make an as­ trips annually so the annual average trap even before moulting. sessment of ghost-pot mortality and loss rate was 29 percent. We will use 25 Toward the end of our Phase III study claw loss for 1976; 1973 through 1975 percent for the purposes of this assess­ there were mass mortalities in the ghost are similar. The number of traps and ment. traps. One possible cause would have lobster landings are preliminary figures Annual inshore trap losses: 525,000 been gaffkemia, a lobster disease. gathered by NMFS. ghost traps. Rabin (1965) found that it is endemic in The inshore fishery landed Annual offshore trap losses: 18,000 the natural lobster populations in the 25,812,000 pounds (11,615,400 kg) ghost traps. Woods Hole area. He also states that using 2,100,000 traps; an annual land­ Another category ofghost traps is the virulence may be a condition of the ings per trap of 12.3 pounds (5.53 kg). cumulative trap losses. From the inter­ holding impoundment. There are no The offshore trap fishery landed view data we found that about one-third obvious signs of the disease though it is 4,220,000 pounds (1,899,000 kg) of the traps offshore are all-metal or known to be transmitted through using 72 ,000 traps; an annual landings plastic. If we give these traps a 3-year wounds. Higher temperatures speed the per trap of 58.6 pounds (26.4 kg). The ghost fishing life span, there will be progress of the disease (Stewart et a!., annual landings per trap is a rough 12,000 additional traps ghost fishing 1969). It can be shown that when our figure as many traps are only in the offshore each year. Due to lack of data mass mortalities occurred. conditions fishery for a few months. Another point on inshore trap types lost, we will not were ideal for a gaffkemia epidemic. is that the landings, especially from in­ evaluate inshore cumulative ghost Another cause of trap mortality may shore, represent only a small part of the fishing, but it may be significant. be predation by other species, espe­ actual catch, i.e., 20 percent where the To determine what the inshore mor­ cially if the lobsters were recent moults throwback ratio is 4 to I. tality per ghost trap should be, we as­ Twenty-five percent is presently the sumed that half the lobsters in the mis­ most accepted average figure for annual sing category in our experiments died in ·Stein, L.. S, Jacobson. and J, Atema, 1975, inshore trap loss rate. To see if we could the traps. This gives us 0.5 pounds Behavior of lobsters (Honwrt/s americonLls) in a use this figure for the offshore fishery, (0.23 kg) per trap in Phase I, 1.3 semi-natural environment at ambient tempera­ the port interview data from offshore pounds (0.58 kg) per trap in Phase II, tures and under thermal stress, Unpubl. man­ user., 49 p, Woods Hole Oceanogr. Insl. Tech, lobster boats were analyzed. 4.2 pounds (I .9 kg) per trap in Phase III Rep. 75-48, Port interviews are conducted by nonvented, and 1.0 pounds (0.45 kg)

64 Marine Fisheries Re\'ielV per trap in Phase III vented. Annual PREVENTIVE SOLUTIONS convinced of the value of this exercise ghost-trap mortality would be higher he may replace the degradable mech­ for the following reasons: I) There Reduced Effort anism with a nondegradable one. In the were lobsters still entrapped at the end It becomes obvious that the best way sablefish (blackcod) pot fishery, some of each phase of the experiments. 2) to reduce trap-related injury and mortal­ fishermen laced up the escape vent with Many of the lobsters were released ity is to reduce the number oftraps. Any nylon instead of cotton twine. from our traps when catch escape reduction in the number of traps will panels opened and when our traps were cause a corresponding reduction in trap Sublegal Escape Vents raided. 3) Our experiments did not con­ losses and thus in ghost-fishing mortal­ It has been demonstrated many times tinue into the fall when greater mortll.l­ ity. If the same landings can be sus­ that sublegal escape vents reduce the tained with a 50 percent reduction in ity was probable. catch of sublegals. Pots that retain We conclude that a conservative traps inshore, then close to 700,000 fewer lobsters are less destructive to the figure for the inshore annual ghost­ pounds (315,000 kg) of lobsters will be catch both in the normal and ghost­ fishing mortality rate would be 2.5 saved from unprofitable deaths; over fishing modes. If all traps inshore used pounds (1.12 kg) per nonvented trap $1. I million in landed value. sublegal escape vents of 45 mm. the and 1. 5 pounds (0.67 kg) per vented (45 Cutting Losses ghost-catch mortality rate would drop rnrn) trap. (For this assessment we are 1.0 pound (0.45 kg) per trap for a sav­ neglecting legal size differences be­ It may be possible to decrease pot ing of 525,000 pounds (236,250 kg), or tween states.) We can derive similar losses both inshore and offshore sub­ roughly $870,000 in landed value. The figures by taking landings per inshore stantially below levels of 20-30 per­ many additional advantages of sublegal trap, assume a throwback ratio of 4 to 1 cent. To do this the first step needed to escape vents have already been re­ for nonvented traps, and arrive at a be undertaken is a survey to identify viewed elsewhere. catch of61.5 pounds (27.7 kg) per trap. quantitatively the causes of pot losses A ghost trap at 10 percent of this and the methods developed by lobster­ Catch Escape Panels rate (our field experiments) for a ghost men to reduce losses. catch of 6 pounds (2.7 kg) per trap. As mentioned previously, there are The sublegal escape vent and the de­ Using a 40 percent mortality rate many areas in the lobstering operation gradable section could be combined (known mortality plus one-half the that can be improved upon to reduce into one unit. Our catch escape panel is missing category) gives us 2.4 pounds losses. Trapezoidal pots may be less 8X8 inches (20.3X20.3 cm) and con­ (1. I kg) per nonvented trap. susceptible to loss than half-round pots. tains a I ¥I-inch (45 mm) high x6-inch By an intuitive process we assumed a Many lobstermen may be using in­ (15.2 cm) long sublegal escape vent. mortality rate of 6 pounds (2.7 kg) per sufficient ballast or an inferior pot This panel is affixed over a 6- x 6-inch offshore nonvented trap based on warp. There are indications that some (15.2- x 15.2 cm) hole cut into the par­ offshore catch rates. types of buoys are better than others lor end of the pot and is attached by two Anuual inshore ghost trap mortality: (Spurr, footnote 2, p. 19). Multipot hog-ring hinges on the bottom and a 525,000X2.5=1,312,500 pounds trawls may suffer fewer losses than degradable link on the top. (590,625 kg). single pots inshore. In the closed state the panel allows Landed value: $2,179,000.00 (1976 sublegal-sized lobsters to escape average price: $1.66 per pound). Degradable Sections through the vent. After a period of time Annual offshore ghost trap mortality: To prevent a long-term cumulative the degradable link fails, allowing the (18,000 + 12,000) x6.0 = 180,000 ghost fishing problem, the solution panel to drop open so all trapped pounds (81,000 kg). might be to have all virtually nonde­ lobsters can escape. Landed value: $299,000.00. gradable pots contain a section that The choice of panel material would To assess claw loss we used 10 per­ would rot out in about a year's time. probably depend on whether the panel cent for the number of lobsters with one When this section fails it should leave is provided by the State or made by the or more missing or small regenerate an opening with a minimum dimension lobsterman. The choice of degradable claws. We used 15 percent as the at least equal to the diameter of the head link would depend on the failure-time weight reduction per cull lobster. Using opening. The degradable section could required. 30,000,000 pounds (13,500,000 kg) as consist of wood, natural fiber, or un­ For the purposes of this discussion, the annual trap caught landings, we get treated iron wire. As mentioned in the we will assume that the panels would be 450,000 pounds (202,000 kg), for a introductory paper (Smolowitz, 1978), mass-produced by the States, similar to value of $747,000.00, lost due to mis­ this approach has been taken in several the way auto license plates are, and sing and/or regenerate claws. fisheries already. contain a stamped license number. There are additional losses that can­ To solve the short-term ghost fishing Lobstermen could, for example, be re­ not be evaluated here. These are the problem is more difficult. Since the de­ quired to buy one panel annually for possible decrease in moult frequency gradable mechanism would be required each pot fished. Double-parlor pots and growth increments due to injuries to fail sooner, it would be more bother­ would be required to have two panels, and claw loss sustained in the traps by some for the fishermen to keep replac­ one on each parlor. sublegals. ing them. If the is not fully The possible advantages of the catch

May-June /978 65 HAB/PQT - wilhaul head funnel

Figure 3.-Basic tire habipot design with two entrance vents and drainage holes. The tires were not negatively buoyant enough and had high drag characteristics during hauling. escape panel are analyzed in the follow­ 6. Reduces and eventually ends A lot more work is necessary to develop ing discussion. ghost fishing. A sublegal escape vent, a selective nonentrapment type of pot. I. Allows the State to have more by reducing the number of lobsters re­ CONCLUSIONS accurate knowledge of the number of tained, should reduce ghost-fishing pots being fished. If the State issues the mortality. When the degradable link I. The main ghost-fishing danger lies panels, not only will it have a solid fails, the pot will no longer fish. in the cumulative effect on the inshore estimate of the number of pots being 7. Improves quality of catch. Fewer fishery if the majority of fishermen start fished but also of how many are being lobsters in the pot should cause less using all-metal and/or plastic traps, a lost. conspecific-inflicted injuries, e.g., trend that is well under way. We re­ 2. Easier to enforce regulations due claw loss. commend that all traps be required to to the high visibility of the panel on the 8. Controls bycatch. Pots with sub­ have one untreated wood lath in their pot. This is one of the major advanatges legal vents let out most . This may construction which, upon rotting out, over lath spacing as a means to regulate be more of a problem where the crabs leaves an opening equal to or greater sublegal catch. All the enforcement are sold commercially. than 75 x I50 mm. officer has to do is to see the panel and 9. Increases pot efficiency. In areas 2. Any reduction in the total number he knows it has the correct vent size. where there is a large population of of traps used will have positive results 3. Uniform size of sublegal vent al­ legal lobsters, the sublegal escape vent in reducing ghost fishing and trap­ lows more accurate control of pot selec­ should allow more of them to be related injuries and mortality even if the tivity. The sublegal vent can be accu­ caught. fishermen increase effort. rately sized and constructed so as not to 3. We recommend field tests with a swell or be worn away. Habipots 47-mm escape vent, as indications are 4. Decreases damage to sublegal that this size vent will substantially in­ lobsters. This is an advantage of any During this project we constructed crease the overall bene fits to the fishery sublegal venting mechanism. and started to test several designs of attributed to sublegal venting, with 5. Decreases illegal sales of sublegal habipots, but time and money consider­ only a negligible reduction in legal lobsters. This is not known for sure, ations did not allow for completion of catch. because many lobsters just under legal the work. Two types of habipots con­ 4. We recommend that a study be size will still be retained. These are the structed out of old automobile tires undertaken to determine the causes of lobsters a dishonest lobsterman would (Figs. 3 and 4) were fished with limited trap losses and the means to prevent or sell. success; they caught sublegallobsters. reduce them.

66 Murine Fisheries Rel'in\, HOmLJrus americanus, in commercial and re­ search catches off the Maine coast. Fish. Bull., U.S. 74:719-724 HABIPOT - wilh head funnel Leakey, R. D. 1965. Folding traps built to be escape proof. Natl. Fisherman, October 1965, p. 13. McLeese, D. W. 1956. Effects of temperarure, salinity and oxygen on the survival of the . J. Fish. Res. Board Can. 13:247-272. Moody, J. A. 1965. Pilot studies in Saco Bay, Maine on chemical bait, phototropism, and escape of the American lobster. Bio­ Dynamics, Inc., Cambridge, Mass., 16 p. Morgulis, S. 1916. The influence of fasting on lobsters. Trans. Am. Fish. Soc. 45:198-201. Munro, J. L. 1973. Large volume stackable fish traps for offshore fishing. Gulf Caribb. Fish. Inst. Proc. 25:121-128. New England Marine Resources Information Program. 1972. Forget the mice' It's a better lobster trap that's needed. New Eng/. Mar. Res. Inf. 34: 1-2. Sea Grant No. RIU-2-72-34. Prudden, T. M. 1962. About lobsters. Bond Wheelwright Co., Freepon, Maine, 170 p. Rabin, H. 1965. Srudiesongaffkemia, abacterial disease of the American lobster, HOmLJrus americanus (Milne-Edwards). J. Invenebr. Pathol. 7:391-397. Rathbun, R. 1887. The crab, lobster, crayfish, rock lobster, shrimp, and prawn fisheries. In George Brown Goode (editor), The fisheries and fishery industries of the United States, Sec. V, vol. II, p. 627-810. Gov. Print. Off., Wash., D.C. Scarralt, D. J. 1965. Predation of lobsters (Homarus americanus) by Anonyx sp. (Crus­ tacea, Amphipoda). J. Fish. Res. Board Can. 22: 1103-1104. ____. 1973. Claw loss and other wounds in commercially caught lobsters (Homarus SECTION A-A americanus). J. Fish. Res. Board Can. 30: 1370-1373. Scrivener, J. C. E. 1971. Agonistic behavior of the American lobster HOmLJrus americanus Figure 4.-A head funnel was incorporated into the basic design to prevent (Milne-Edwards). Fish. Res. Board Can., escapement during hauling. Tech. Rep. 235, 128 p. Sheldon, W. W., and R. L. Dow. 1975. Trap contribution to losses in the American lobster fishery. Fish. Bull., U.S. 73:449-451. 5. We recommend that all research­ tough job of typing the annotated bib­ Smolowitz, R. 1. 1978. Trap design and ghost ers, where applicable, use a standard­ liography. fishing: An overview. Mar. Fish. Rev. ized trap to eliminate variable of selec­ 40(5-6):2-9. tivity and trap efficiency and thus allow Stewan, J. E., J. W. Cornick, D. M. Foley, M. LITERATURE CITED F. Li, and C. M. Bishop. 1967. Muscle weight for better comparisons of data collected relationship to serum proteins, hemocytes. and throughout the lobster areas. hepatopancreas in the lobster, Homarus Burgess, J. 1969. with anchor. Fish. americanus. 1. Fish. Res. Board Can. ACKNOWLEDGMENTS News (Lond.) No. 2932, 15 August, 6. 24:2339-2354. Emmel, V. E. J905. The regeneration of lost -, , and B. M. Zwicker. Dozens of people were involved in pans of the lobster. Commissioners of Inland 1969. Influence oftemperature on gaffkemia, a the collection ofdata used in this report, Fisheries of Rhode Island, 35th Annu. Rep., p. bacterial disease of the lobster, Homarus among them lobstermen, port agents, 81-117. americanus. J. Fish. Res. Board Can. Hipkins, F. W. 1972. Dungeness crab pots. U.S. 26:2503-2510. statisticians, divers, boat operators, Dep. Commer., NOAA, Natl. Mar. Fish. Thomas, H. 1. 1959. A comparison of some and students. Hopefully the authors Serv. Fish. Facts-3, 13 p. methods used in lobster and crab fishing. Scott. have done justice to this hard-earned Krouse, J. S. 1977. Incidence of cull lobsters. Fish. Bull. 12:3-8. data. We would like to especially acknow­ MFR Paper 1310. From Marine Fisheries Review, Vol. 40, No. 5·6, May-June ledge John Lamont who performed the 1978. Copies of this paper, in limited numbers, are available from D822, User Services Branch, Environmental Science Information Center, NOAA. Rockville. near-endless task of preparing the il­ MD 20852. Copies of Marine Fisheries Review are available from the Superin­ lustrations for this report. Margaret tendent of Documents, U.S. Government Printing Office. Washington. DC Mehmel also deserves praise for the 20402 for $1.10 each.

May-JI/ne /97R 67