Tropical Spiny Lobster : an Overview of Their Biology, the Fisheries and the Economics with Particular Reference to the Double Spined Rock Lobster P

SPC/lnshore Fish. Res./WP.18 17 March 1988

ORIGINAL : ENGLISH

SOUTH PACIFIC COMMISSION

WORKSHOP ON PACIFIC INSHORE FISHERY RESOURCES (Noumea, New Caledonia, 14 - 25 March 1988)

TROPICAL SPINY LOBSTER : AN OVERVIEW OF THEIR BIOLOGY, THE FISHERIES AND THE ECONOMICS WITH PARTICULAR REFERENCE TO THE DOUBLE SPINED ROCK LOBSTER P. penicillatus.

JIM PRESCOTT Fisheries Biologist Fisheries Research Dept of Fisheries and Marine Resources Papua New Guinea

A Keynote Address to the Workshop SPC/Inshore Fish. Res./WP.18 Page 1 TROPICAL SPINY LOBSTER: AN OVERVIEW OF THEIR BIOLOGY, THE FISHERIES AND THE ECONOMICS WITH PARTICULAR REFERENCE TO THE DOUBLE SPINED ROCK LOBSTER P. penicillatus.

INTRODUCTION

Four taxonomic families are commonly refered to as lobster. Of these there are three families which include commercially valuable species. In this paper the term lobster will generally refer to what is commonly know as spiny or rock lobster, of the family Palinuridae. However, particularly in reference to the economics lobster will be used to include the clawed lobster of the family Nephropidae and the flat or slipper lobster of the family Scyllaridae with which the spiny lobster compete on the world market.

Developing lobster fisheries have several distinct advantages over other fisheries. With relatively simple technology lobster can be caught and held alive in village situations, alleviating the need for expensive preservation methods such as ice or freezing. Because lobster is a high value product there is greater room for absorbing the cost of transporting the product to the market place. Finally, because there is strong international demand, not to mention local demand in many places, there is little difficulty in marketing the product.

Though there are a number of species of spiny lobster of the genus Panulirus in the South Pacific Commission area only three occur in large enough numbers so as to offer some commercial potential. In Papua New Guinea and Australia P.ornatus supports a dive fishery that produced more than 400 tonnes of tails in 1986. In Papua new Guinea alone catches had an export value of 1.0 and 1.3 million PNG Kina in 1985 and 1986 respectively. During these years lobster has ranked second, after prawns, in export value. However, this is an exception in the Pacific area for a variety of reasons. Throughout most of the remainder of Oceania P. penicillatus or P. versicolor are the most abundant species, and only P. penicillatus is normally in densities high enough to warrant harvest for commercial purposes.

Worldwide, lobster support many large and lucrative fisheries. While there have been several notable fisheries where catches have dropped dramaticaly due to overfishing, the catches in many are stable and in some places are even supporting increased effort and catches. Overall the trend is for an increased total lobster catch. The United States is the single largest importer of lobster and lobster products. Demand in the United States is thought to be increasing and a real price increase on the order of several percent forecast in the near term, that is to say that the increases in demand are greater than those of supply. How this will affect the value in the currency in the country of origin will depend largely on the value of the United States dollar relative to that currency. SPC/INSHORE FISH.RES./WP.18 Page 2

TAXONOMY

There are four families of lobster in the Order Decapoda. Three of these, Nephropidae (clawed lobster), Palinuridae (spiny lobster), and Scyllaridae (slipper lobster) are found in the Pacific. The fourth family Synaxidae (coral lobster) are found only in the Indian Ocean. The clawed lobster are not well represented in the pacific and are not commercial anywhere in the SPC area at the present time and are therefore not covered in this paper. The slipper lobster will be discussed in another presentation so are therefore not discussed.

Three genera of spiny lobster are found in the tropical central- west Pacific. The genus Panulirus is richest in terms of numbers of species and dominates numerically. Six species are widely distributed in the tropical western Pacific, however only P. penicillatus has crossed the east Pacific barrier (Johnson, 1974) and is found as far east as the west coast of Mexico (Briones and Lozano 1982). Two species. P. marginatus and P. pascuensis have very restricted distributions and are known only from the Hawaiian archipelago and Easter Island respectively.

The genus Puerulus, not to be confused with the Palinurids last larval stage of the same name, is restricted to deep shelf areas from East Africa to Papua New Guinea and the Solomon Islands, and perhaps further east. Justitia is known only from Japan, Hawaii and Papua New Guinea, but undoubtably has a wider distribution than that. Both Puerulus and Justitia are small lobster with little commercial value.

Table 1. Species of the genus Palinurus, Justitia, and Puerulus found in the tropical central and western Pacific are listed with their distribution and commercial production where known.

Genus Species Range Commercial

Panulirus homarus Indo-Pacific not in Pacific " penicillatus Red Sea - Mexico in some areas " longipes " femoristriga Indo-Pacific yes in Tonga? " ornatus Indo-Pacific yes in PNG " versicolor Indo-Pacific very limited " polyphagus Indo-West Pacific not in Pacific " marginatus Hawaii only yes " pascuensis Easter & Pitcairn Is. Puerulus angulatus Indo-West Pacific no Justitia longimanus Hawaii and ? Aquarium trade " j aponicus PNG and ? SPC/INSHORE FISH.RES./WP.18 Page 3

The taxonomy of P. longipes femoristriga and P. homarus requires review. P. longipes femoristriga appears to exibit considerable local variation in the SPC area. One conspicuous variation is in the colouring of the antennules. George (1974) states that there are two taxa. George (1974) further suggests that there may be three taxa of P. homarus however it is likely that only one of these is found in the SPC area.

HABITAT

Virtually all shallow water habitats in the tropical west Pacific are occupied by one or more species of spiny lobster. Each species has a prefered habitat, however there is a great deal of overlap and it is not uncommon to find up to four species co habiting a single reef along the southern coast of Papua New Guinea, for example. Certain species are far more specific in their habitat requirements than others. The greatest contrast is perhaps seen between P. ornatus and P. penicillatus in this regard. P. ornatus has been found from a depth of 100 fathoms on the outer slope of the Great Barrier Reef to areas with extremely high sediment load and reduced salinity characteristic of the reefs near the mouth of the fly river. P. penicillatus is found across nearly a 60 degree range in latitude from rocky shores to coral reefs, but with the common feature of clear oceanic waters and high energy wave action typical of windward exposures. This habitat is remarkably similar in terms of salinity, disolved oxygen, and turbidity and the variability of these factors despite significant latitudenal changes.

The prefered habitat of P. penicillatus as discussed above is the windward exposures of fringing rock or coral reefs. It shelters in deep recesses during the day at depths to ten metres and but most frequently much shallower than that. At night it forages over the reef face, crest and flats, thus exploiting a much larger habitat than merely that where it dens. It is also common on leeward barrier reefs and in reef passages when there is sufficient water movement. The larvae must settle in the adult habitat as that is the only place small juveniles have been found by the author. These were found deep in the caves and crevices used by the adults to shelter by day.

The lower energy habitat of P. longipes femoristriga is contiguous with the P. penicillatus habitat at its lower boundary, and away from areas of intense wave action. Small juveniles of" this species have not been observed but it is presumed that they occupy the same habitat as the adults. SPC/INSHORE FISH.RES./WP.18 Page 4

In still lower energy areas, frequently amongst live acropora and other reef building corals, P. versicolor dominates. It is less cryptic than either P. penicillatus or P. longipes femoristriga and can frequently be seen during the day in coral bommies and under plate corals. P. versicolor appears to be more tolerant of terrestrial influences than either P.penicillatus or P. longipes femoristriga and can be found on reefs exposed to high turbitiy and reduced salinity. The juveniles inhabit inshore areas as well as the more typical adult reef. They are conspicuous by their long white antenna. Post larvae are often seen under floating moorings and rafts. It is not known whether these lobster move to the reef successfully or whether they die.

Panulirus ornatus is most common in areas with a strong terrestrial influence. It is frequently found on lagoon bottoms and deep channels emanating from mangrove communities. In the Torres Strait area this species is highly migratory, making as much as a 500 km breeding migration to the Eastern Gulf of Papua and thus passes through a variety of habitats during its life cycle, in thhis part of its distribution. Elsewhere in its distribution large scale migrations have not been noted and it is likely it is more resident in one habitat. Some larval settlement is known to take place in its reef habitat, however, the principal areas for settlement in Torres Strait have not been documented.

Panulirus homarus inhabits areas of relatively high energy but with strong terrestrial influence, including high turbidity and reduced salinity. The author has caught adult specimens at Bourai in New Caledonia, Parama reef at the mouth of the Fly river, and Yule Island at the eastern end of the Gulf of Papua. Larval settlement was found in an estuary east of Port Moresby on badly fouled boat hulls.

Panulirus polyphagus is the least common member of its genus in the SPC area. In parts of its range where there are extensive muddy shelf areas it is commercially important, however this habitat is extremely restricted in the SPC area. Specimens are ocassionally taken by prawn trawlers in the Gulf of Papua. A number of specimens were also recently caught by Fisheries Research in the western part of the Torres Strait, and one was caught by the author over seagrass beds in Torres Strait.

REPRODUCTIVE BIOLOGY

The sexes of all lobster are separate and no sex reversals are known. The two sexes in the genus Panulirus are distinguishable at an early age by external secondary sexual characteristics. Females can be indentified by the paired external gonopores at the base of the third pair of walking legs the presence of a chelate fifth walking leg and biramous pleopods. In contrast the male has large paired openings of the gonads at the base of the fifth pair of walking legs, and uniramous pleopods. Frequently there are also striking differences in the length of the walking legs of the males and females of equal size which is brought about by changes in the allometric growth of the legs with the onset of sexual maturity (Gordon 1960, George and Morgan 1979, Grey 1979). SPC/INSHORE FISH.RES./WP.18 Page 5

In P. penicillatus there is a striking change in the allometric growth of the cephalothorax in males.

There are no published reports of mating in any of the species found in the SPC area. The author has however witnessed mating of P. ornatus. Courtship in this case involved the male continuously touching the female with the dactyls of the first three pairs of his walking legs while supporting himself and following the female on his hind legs for a period of fifteen minutes. Eventually this ended with the male making a frontal approach and lifting the female and into contact with his genital openings. It would appear that mating takes place only when the females are in certain stages of ovarian development in this species.

The same is probably true of P. penicillatus as well since few females are found with un-used spermatophores, indicating the spawning takes place shortly after mating and no further mating normally takes place until the female approaches full gonadal development again. During mating the male deposits the spermatophoric mass on the sternum of the female. This mass consists of a sperm tube in an acellular matrix. The female carries the spermatophore until she spawns at which time it is scratched open releasing the sperm. Multiple spawning may be possible from a single spermatophore.

During spawning, the eggs pass from the gonopores to the brood chamber formed by the pleopods and the uropods. Here the eggs adhere to the ovigerous setae on the endopods. In the Solomon Islands, where average seawater temperature was 28-29 degrees Celsius, incubation period was for a period of approximately three weeks for P. penicillatus. In higher latitudes where water temperatures are reduced incubation takes longer. Morris (1968) and McGinnis (1972) noted incubation periods of 33 and approximately 30 days respectively for P.penicillatus in Hawaii.

Maturity in lobster is in most cases only studied in the female because of the lack of obvious external evidence in the males. A number of characters in females have been used to define maturity, including the presence of spermatophores and ovigerous setae, however that most used and of the greatest significance is the presence of an external egg mass. Size at sexual maturity is most frequently understood to be the size at which 50 % of the females are carrying eggs, ovigerous, during the breeding season, which is continuous for the most common species in the SPC area (see below).

Size at sexual maturity for P. penicillatus was estimated to be to be between 75 and 79 millimetres carapace length, Figure 1. Fifty percent of the females were not actually ovigerous until the 80 to 84 millimetre size range, however due to an apparent increase in spawning frequency this over-estimates the mean size at maturity (Prescott unpbl). In Tonga, Zann (1984) found that 50% of female P. penicillatus were ovigerous in the 75 to 79 millimetre size range, Figure 1. The smallest ovigerous female in the Solomon Islands was 50 millimetres (Prescott unpbl.) and 55 millimetres in Tonga (Zann 1984). MacDonald (1982) found the the smallest ovigerous P. versicolor to be 82 millimetres in Palau. SPC/INSHORE FISH.RES./WP.18 Page 6

Spawning appears to be continuous in P. penicillatus once reproductive maturity is reached. However as noted above , the frequency of spawning varies with the size of the female, Table 2. It appears that there is a trend towards a reduction in breeding frequency as females grow towards their maximum size in the populations studied in the Solomon Islands and Tonga. This trend is not unique to P. penicillatus and has been noted in P. argus (Munro 1974) (Peacock 1974). Changes in spawning frequency may be explained by the length of the intermoult period which becomes progressively longer as the lobster increases in size. No significant seasonal variations in the percentage of ovigerous females was noted in the Solomon Islands, Figure 2. In the main Hawaiian Islands where P. penicillatus also spawns continuously spawning is reduced during the winter months ( McGinnis 1972). No seasonality was found in the spawning of P. versicolor in Palau by MacDonald (1982).

Table 2. The number of estimated broods per year carried by females in the Solomon Islands in five millimetre carapace length size intervals from the assumed mean size at maturity, are shown.

size 75- 80- 85- 90- 95- 100- 105- 110- interval 79.9 84.9 89.9 94.9 99.9 104.9 109.9 114.9

broods/ year 7.8 9.5 10.5 10.1 11.2 11.3 10.2 9.2

The fecundity of P. penicillatus was studied in the Solomon Isalands (Prescott unpubl) and Tonga (Zann 1984). In both localities egg batch size was similar. The linear relationship of egg number to carapace length is shown in Figure 3, and regression statistics are shown in Table 3.

Table 3. Least Square linear regression equation parameters are shown for regressions of egg number on carapace length for P. penicillatus in the Solomon Islands and Tonga.

locality sample Y regression correlation number intercept coefficient coefficient

Solomon Islands 12 -403037.7 7761.3 0.90

Tonga 12 -482700.0 8712 0.780

The reproductive , or egg producing, potential of the poulation is a function of the fecundity of the the females in of all sizes, the frequency of spawning and the number of females of each size. The relative contribution to the total reproductive output by five millimetre size intervals was estimated using a constant natural mortality rate (M) of 0.43, fecundity and spawning frequency data. Shown in Figure 4, this demonstrates that a substantial contribution to the reproductive potential is from small lobster. SPC/INSHORE FISH.RES./WP.18 Page 7

LARVAL BIOLOGY

The larval biology of the lobster species found in the SPC area has not been studied, though it is likely that there is little difference between these species and the temperate water relatives that have been better studied. In temperate water Palinurids there is some debate over the naming of the first stage. A number of authors have described the first stage after hatching as a naupliosoma in a variety of species. However, this stage may be the result of premature hatching. The phyllosoma stage is more widely recognised as the first free swimming larval stage.

The larval period is long in the Palinurids with times of 4-22 months (Phillips and Sastry 1980). In most species however larval periods of 9-12 months are more unusual, although it may be 3-9 months for P. ornatus in the Torres Strait area (Trendall pers comm). During the larval period phyllosomata go through a number of stages, or instars. In P. cygnus this numbers nine and is probably typical of the other species in the genus.

Phyllosomata are known to undergo regular diurnal vertical migrations. These migrations allow larvae to take advantage of surface and deeper currents and in doing so are able to effect some control over their transport. Studies of Palinurid larvae in the Southern Hemisphere indicate that the majority of larval development takes place well offshore (Phillips and McWilliam 1986). Phyllosomata of P. cygnus have been found as far offshore as 1500 km which was the range of sampling (Phillips et al. 1979). Johnson (1974) found phyllosomata of P. penicillatus as far as 2000 nautical miles from the Galapagos Islands which was the nearest likey source. It would appear that P. penicillatus larvae are exceptional in their oceanic distribution and probably in the length of the planktonic larval phase.

Phyllosoma moult into a final larval stage termed the puerulus. Puerulus are able to swim with the use of the pleopods and by abdominal flexures. Pueruli of P.cygnus are able to maintain a constant swimming speed of 15-46 cm/s (Phillips and Olsen 1975). Other species have been found to be capable of slower but none the less constant swimming speeds. The swimming ability of the puerulus stage makes it an important link between the pelagic and benthic phases of the lobsters' life history (Phillips and McWilliam 1986). Phillips and McWilliam (1986) provide the best review of larval biology.

Success in this phase of the lobsters life history may be the most critical factor in determining later recruitment to the fishery. There are some reefs where lobster are definitely shelter limited, however, the majority appear to support lobster populations at levels below the carrying capacity of the reef. Granting that P. penicillatus is very cryptic, small juveniles and post larvae are rarely seen. If rates of larval settlement were high undoubtably more small lobster would be observed. Rates of larval recruitment probably vary significantly between different areas. SPC/INSHORE FISH.RES./WP.18 Page 8

Small remote reefs presumably receive fewer recruits than reefs closer to areas with a larger total population size and greater reproductive output. If this is true then total yield can be expected to vary considerably between reefs.

It is assumed that larval recruitment is a fairly continuous process for P. penicillatus given that reproduction is continuous. Data from the Solomon Islands support this as no modes were evident in the monthly lenght frequency data. This apparently does not hold for the species in Tonga where length frequency data have been used to estimate growth rates. In P. ornatus recruitment is seasonal in the Torres Strait area.

While larval recruitment is probably relatively continuous it may not be constant. In the western rock lobster, P. cygnus. and more locally P. ornatus. larval recruitment appears to fluctuate widely for a given breeding stock size. For example in 1985 an extremely strong year class of 2+ P. ornatus recruited into the Torres Strait fishery. Catches in 1985 and 1986 set new records as a result. Though no reliable estimate of the size of the breeding stock that produced that year class was available, it is thought to have been relatively small as a result of intensive fishing by trawlers during the breeding emigration. Environmental factors probably contribute significantly to the observed variability.

GROWTH

Growth can be measured in either weight or the length of an animals body or body part. Lobsters are most frequently measured in the field as opposed to weighed. In all palinurids the reference measurement is carapace length, measured dorsally from the ridge running between the supraorbital spines to the posterior margin of the carapace. Lengths are preferable to weights as a measurement due to the latter being affected by limb loss, the reproductive condition and the difficulty of obtaining accurate weights in difficult field situations.

Growth in length or weight takes place during the process of ecdysis, or moulting, and is thus stepwise and dependent on the frequency of moulting and the increase in size or weight at each moult, termed the moult increment. Mauchline (1977) found log -linear relationships between the length of intermoult period and the size of the crustaceans he worked with, and between the moult increment expressed as a percentage of the reference measurement, and length. The moult increment, or growth factor as Mauchline (1977) refers to it, is inversely related to length so that as crustaceans grow the period between moults increases and the proportional increase in length decreases.

Relatively few studies have separated the two components of growth as it is difficult to measure the intermoult period in the field, and without this it information is difficult to determine the moult increment. The intermoult period has been most often estimated from mark and recapture data by determining the proportion of recaptures that had moulted within different periods of time at large (Morgan 1980) . SPC/INSHORE FISH.RES./WP.18 Page 9

This method assumes continuous moulting throughout the year, which is reasonable in most parts of the tropical Pacific where there is little variation in water temperature, although the method would fail to work with P. ornatus in Torres Strait, for example, where regular moulting is interrupted by the breeding emigration.

The majority of lobster growth studies have used growth data from mark and recapture studies. Since the wide spread use of computers these data have frequently been analysed by one of several computer programs developed primarily for the growth of fishes. The most commonly used growth model is that of von Bertalanffy (1938) and has been found to be an adequate model if lobster growth in most regards (Morgan 1980) .

Both methods were applied to growth data from P. penicillatus in the Solomon Islands. The most realistic growth curve was generated for the females by using the data on moult increment and intermoult period. The predicted size at age data from this method was then fitted by the Gulland-Holt computer program to calculate the parameters of the von Bertalanffy growth equation, see Table 4. The females' growth curve is shown in Figure 5a. Growth curves were generated for the males by computer and by using the information from intermoult period and moult increment. The curves were similar in both cases. The males' growth curve generated by the Gulland-Holt program is shown with the females' in Figure 5a, and the parameters of the von Bertalanffy growth equation are presented in Table 4.

The growth of both sexes in the Solomon Islands is similar to that reported for this species in Enewetak by Ebert and Ford (1986), Figure 5b. The maximum length of both sexes also agrees well with the observed maximum sizes in the Solomon Islands, and Papua New Guinea. Certainly there may be wide variations in growth across P. penicillatus wide range and in particular across a latitude gradient. The author has seen extremely large individuals in both New Caledonia and Kure Atoll, North West Hawaiian Islands, that are far beyond the maximum lengths observed elsewhere in the tropical Pacific, and large specimens have been measured in Tonga by Zann (1984).

In general the growth of P. penicillatus appears to be more rapid than its colder water relatives, but not as fast as P. ornatus (see paper by Trendall, this workshop).

Table 4. Parameters of the von Bertalanffy growth equation are shown for growth curves for P. penicillatus in the Solomon Islands, and Enewetak (from Ebert and Ford 1986).

sampling location sex 1^, growth coefficient t

Solomon Islands male 143.9 0.294 -0.375 female 113.4 0.499 -0.285

Enewetak male 146.5 0.211 -0.165 female 96.5 0.580 -0.092 SPC/INSHORE FISH.RES./WP.18 Page 10

MORTALITY

Mortality was estimated for the populations studied in the Solomon Islands and Enewetak. In the Solomon Islands age frequency distributions were produced, based on the predicted growth rates of each sex and the size frequency distributions. Mortality was estimated graphically from the age distributions by the methods of Gulland (1969, 1983). Using this method, both males and females had a mortality rate of approximately 0.40. Fishing mortality was neglible in the study area, so consequently the mortality estimates are natural mortality only.

Ebert and Ford (1986) estimated mortality at Enewetak directly from the growth coefficient, maximum and mean lengths, and the length at first recruitment using the Beverton and Holt formula (1956) M - KCS,^ - Sbar)/(Sbar - S ). Mortality estimates were different from those for P. penicillatus in the Solomon Islands. Males and females both had mortality rates of approximately 0.25. Application of this method to the data from the Solomon Islands yielded mortality estimates of 0.48 and 1.17 for males and females respectively. In this instance it is thought that the graphical method yielded better estimates.

The natural mortality rates of P. argus was estimated to be on the order of 1.0 in Jamaica, (Munro 1974). In Western Australia the natural mortality of P. cygnus has been estimated to range from approximately 0.2 to 2.0 (Morgan 1980). It would appear from these estimates that the estimate for P. penicillatus at Enewetak may be low.

POPULATION STRUCTURE

The population of P. penicillatus studied in the Solomon Islands was one that had experienced only low levels of exploitation and therefore can be considered as unfished. It was characterised by an excess of females (58%), similar to that studied by Ebert and Ford at Enewetak (1986) where females were 71% of the total catch and in Papua New Guinea where females were 62% of the catch. George (1972) reported a sex ratio close to unity but slightly in favour of females in two samples totalling 430 lobster caught in Lau, Fiji. In Tonga, however, Zann (1984) found the sex ratio favoured males. In each of these cases there was probably statisticly significant differences from equal sex ratios, except in Fiji. Ebert and Ford (1986) believed the sex ratio was skewed in their sample population because of a sampling artifact. They observed that females came further up the reef flat than the males and hence were more likely to be captured by walking on the reef flat, as they did. However, in the samples taken in the Solomon Islands and Papua New Guinea catching was done by diving over the entire range of the habitat. Shaklee (1983) found by electrophoretic methods that the sex ratio of embryos was skewed towards males in P. marginatus and remainded skewed in the postlarvae and adult populations. While the sex ratio in P. marginatus may be skewed in the opposite direction to P. penicillatus in all but one area sampled, it does demonstrate that in at least one species of Panulirus there is a naturally skewed sex ratio from the earliest stages of the life history. SPC/INSHORE FISH.RES./WP.18 Page 11

Both sexes were present in equal numbers in the sampled population of P. versicolor in Palau (MacDonald 1982).

The population structure of four sample populations in the Solomon Islands, Conflict Islands (Papua New Guinea), Tonga, and Enewetak are shown in Figure 6. Note the similarity between the data from each of the locations other than Tonga in regard to mean and maximum sizes. In Tonga although the mean size has been depressed due to fishing mortality, there are still numbers of large animals in the upper size intervals. The largest male in this sample, not shown, was 184 millimetres. As noted above the author has observed the largest specimens of P. penicillatus. P. versicolor and P. lonpipes femoristriga in the highest latitudes of their distribution.

No changes in the population structure were evident during any time of the year or over the 24 month study period in the Solomon Islands. At Enewetak the population structure was assumed to be stable and there was certainly no reason to doubt this from the data presented by Ebert and Ford (1986). In Palau MacDonald (1982) noted that there was no monthly trend in the mean carapace lengths.

In contrast to the relative stability of populations of P. penicillatus and P. versicolor, the population structure of P. ornatus varies markedly during the year in Torres Strait. There significant changes in both the size structure and sex ratio of the population in response to seasonal recruitment and the departure of the breeding emigration, Figures 7-9.

It is important to note that in all populations studied, the size frequency distribution reflects the natural population stucture only at lengths above which the lobster were fully recruited. In the Solomon Islands males and females were fully recruited at carapace lengths of 102 and 88 millimetres, respectively. In Tonga males were said to be fully recruited at 80-85 millimetres and females at 75-80 millimetres (Zann 1984).

POPULATION SIZE

Population estimates have been made for two study areas in the Solomon Islands and and three in Enewetak. In the Solomon Island study, estimates were made from mark and recapture data using the stochastic model of Jolly (1965). The total number of lobster estimated for the two areas was 550 and 160 which translated to a density of 46 to 57 lobster per hectare of habitat. This was equal to approximately 111 and 128 lobster per kilometre of reef edge.

At Enewetak Ebert and Ford (1986) were not able to use short term mark - recapture data to estimate population size and relied on the cumulative catch and catch per unit effort over a short time interval. Their estimates were similar to those made in the Solomon Islands, ranging from a low of 35 to a high of 164 lobster per kilometre of reef edge, and averaging 126 (Ebert and Ford 1986). SPC/INSHORE FISH.RES./WP.18 Page 12

YIELD

Estimates of the yield per recruit and total yield to a fishery were made by Ebert and Ford (1986) for P. penicillatus at Enewetak. The model used was the dynamic pool model of Beverton and Holt (1957). This model allows estimates of yield per recruit (Y/R), for varying rates of fishing mortality and age of recruitment. One important assumption of the model is that Recruitment is independent of stock size. This assumption is most likely valid with regard to P. penicillatus, at least as long as the fisheries remain localized, see discussion on recruitment.

Yield per recruit increased rapidly as a function of increasing fishing mortality (F) to a value of about 0.3. At a rate of 0.5 the average whole weight was approximately 450 grams. Fishing at this intensity would thus translate to an average total yield of about 20 kilograms whole weight per kilometre of reef edge in suitable habitat. This estimate disregards the claim by Ebert and Ford (1986) that the population estimate they made should be increased by a proportion such that the two sexes are represented equally. If the sex ratio was actually at unity, then the yield would have been approximately 28 kilograms per km.

Using data from the Solomon Islands yield per recruit curves were constructed with values from Beverton and Holts' (1959) Tables of yield functions for fishery assessment, Figure 10. This method was used by Munro (1974) to produce yield per recruit estimates for the P. argus fishery in Jamaica.

There are two important features of the yield per recruit curves and the results of Ebert and Ford (1986) in Enewetak. The first is that yield per recruit does not drop until high levels of fishing mortality (F) are achieved. Because catch per unit effort decreases as F increases it is unlikely that levels of F would exceed that for a maximum yield per recruit. Secondly, the introduction of minimum size limits at any size greater than the size at recruitment reduces yield per recruit. In the Jamaican fishery for P. argus increasing the value C (L^/L,,) increased yield per recruit because of the relatively small length at recruitment versus the large maximum size. The same may also be true for Tonga (see paper by Munro, this workshop).

Surplus yield models have been used successfully to model yield in both clawed and some temperate water spiny lobster stocks. The method does not require information on mortality or growth, but does require accurate records of catch and effort over a wide range of effort. It is doubtful that the method would be applicable to the population of P. penicillatus as it assumes that stock and recruitment are dependent in some unspecified way. Therefore the unit stock must be defined and catch and effort for that stock recorded. Defining the unit stock for P. penicillatus is not possible at present, and consequently this method of yield assessment is not possible. SPC/INSHORE FISH.RES./WP.18 Page 13

Zann (1984) estimated that catches in the Ha'apai group, Tonga, were on the order of 20 tonnes whole weight in 1984. Earlier reports stated that annual catches of 36 tonnes whole weight were achieved during the 1960's. It is noted by Zann (1984) that the operation is believed to have collapsed due to overfishing. Unfortunately no mention is made of the area fished during these operations and consequently there is no means for comparison with the estimated yield for Enewetak. Hoogesteger (1980) reported a total catch of 5596kg during a six month period at Christmas Island, Kiribati, with no apparent decline in the catch per unit effort. This catch is equivalent to approximately 47 kilograms per kilometre of reef edge. These catches were made early in the development of the Christmas Island fishery and should be considered transitional. As the standing stock is reduced catch rates and total catch will drop.

Juinio and Gomez (1986) reported lobster catches from eastern Samar, Philippines. Catches in this area ranged from 1.3 to 23.5t lobster tails annually. During 1982-83 P. penicillatus accounted for more than 80 % of the catch, and P. longipes femoristriga 11 %. The largest catch of P. penicillatus reported in the literature is 400 tonnes from Reunion, the Pacific Islands, and the Galapagos Islands (Morgan 1980).

MOVEMENTS

Panulirus ornatus appears to be the only species within the SPC area that migrates to any noticable extent. In the Torres Strait area their breeding biology is characterised by a one directional breeding migration of up to 500km or more (Moore and MacFarlane 1984). After the migration some lobster become resident on several known reefs, but the majority of the lobster move to unknown areas, possibly on the edge of the continental shelf. At the end of the breeding season the lobster disappear from the known areas, however it is not known whether this is due to a movement away from the reef or mass mortality from a combination of the effects of fishing and natural causes. It was previously suggested (MacFarlane and Moore 1985) that there was a mass die off from natural causes. Recent studies indicate that lobster on the breeding grounds are in poor physiological condition and may fail to moult successfully and die. More common in the species inhabiting the vast majority of the SPC area is the relative non migratory behavior and continuous breeding in the same locality over many years.

Short movements by P. penicillatus were noted in the Solomon Islands away from areas that were poor habitat to areas of good habitat. These only took place during incidents where lobster were unintentionally released in areas outside their normal habitat. Movement was limited to distances of about two kilometres. During the mark and recapture study there were very few movements between adjacent study areas. SPC/INSHORE FISH.RES./WP.18 Page 14

FISHERIES

Around much of the world lobster are most frequently caught by trapping with one or more styles of a wide variety of traps. However, only two species in the SPC area, P. penicillatus and P. longipes femoristriga. are known to enter traps readily. Traps placed near dens of P.versicolor have never been successful in the authors experience. Likewise, extensive trapping surveys done in Papua New Guinea in areas with large populations of P. ornatus yielded only the occasional lobster.

Traditionally traps have been used to catch P. penicillatus in Tonga, Western Samoa, and American Samoa (George 1972) and perhaps elsewhere. George also reported catches of up to 15 P. penicillatus per trap night in American Samoa, and smaller catches including P. longipes femoristriga in 19m off the fringing reef and 122m offshore in Vanuatu in rectangular wire mesh traps. A small scale trap fishery for P. penicillatus exists for part of the year in Samar, Philippines but is replaced by spearfishing as sea conditions improve during the calm season (Juinio and Gomez 1986).

Tangle nets appear to be used infrequently though the nets can be an effective means of capture in some places. At Yule Island, which is at the centre of the known breeding grounds for P. ornatus in Papua New Guinea, local fishermen set monofiliment gill nets to catch both fish and lobster on the reef flats where the lobster forage at night. During the day the same fishermen use short lengths of tangle net to encircle coral bommies and catch the lobster as they are chased from their dens by skindivers. Multifilament nets of six inch mesh, three meshes deep have been used to survey other potential breeding grounds in the Gulf of Papua, and have successfully caught P. ornatus as deep as 90 metres.

In Fiji at least one skipjack pole and line vessel was fishing in the Lau Group for P. penicillatus during the off season for tuna in 1984. The fisherman reported that tangle nets were set at low tide behind the reef crest and secured to steel poles that were driven into the reef. The same fisherman claimed that the method was effective and at the time of interview intended to continue lobster fishing with tangle nets. Despite the apparent effectiveness of tangle nets, in areas where fish and shark densities are high and lobster densities are frequently low, the cost of the nets and the damage sustained rule them out as a viable primary capture method for the majority of fishermen. SPC/INSHORE FISH.RES./WP.18 Page 15

Most lobster fishing that is done now involves either skin diving or walking over the shallow reef flats at night. The most widespread fishing method for P. penicillatus is certainly walking on the reef flats. This method has some short-commings however. The first is that it may be more restricted to certain periods by the tides in that the lobster require sufficient water over the flats to come up and forage. There are also the problems of poor visibility from rough conditions due to surface bubbles and turbulence. The authors' prefered method is diving with a waterproof torch. This method allows the diver to see below the bubbles and turbulence and due to the clear oceanic waters characteristic of the P. penicillatus habitat the diver is able to cover a wide area of the habitat as he swims down the reef. It also allows the reef outside the reef crest to be fished which can be productive as the lobster leave their daytime refuges and move onto the reef. It usually means that the minimum number of fishermen involved is three, as one is required to follow the divers in some sort of craft and few divers choose to dive alone at night. The boat must stay, in most cases, outside the breaking waves unless the tide is high enough over the reef flat. If catches are good the boat is a convenient way to carry the heavy catch.

In addition to being nocturnal, most species of spiny lobster are also relatively inactive during the light phases of the moon. During the course of the study in the Solomon Islands it was found that there was little point in fishing during periods of moonlight. Lobster during these times could be seen near the entrances to their dens and would retreat quickly when approached. However, catches were often best several nights after the full moon when the moonrise was several hours after darkness. It appeared that lobster were particularly active during this period which followed perhaps ten nights during which the moon shone for much or all of the night.

In other localities, however it would appear that moon phase may be less important. At Abaiang and Abemama atolls, Kiribati, lobster were caught in good numbers during periods of bright moonlight, Table 5. Hoogesteger (1980) tabled catches and catch per unit effort for P. penicillatus at Christmas Island, Kiribati, which show little change between catches made during dark nights and those made during moonlight nights, Table 5. Further comparative studies in different localities would be interesting from several standpoints. Changes in behavior related to lunar cycles might be explained by the reef topography, and possibly predation pressure. Catches and catch per unit effort for lobster, primarily P. penicillatus are shown for various areas around the Pacific in Table 5. SPC/INSHORE FISH.RES./WP.18 Page 16

Table 5. Catches and catch per unit effort (cpue) of lobster from various localities around the Pacific are shown in the various forms in which they were available. The source of the data is also shown.

moonlight dark night Locality catch cpue catch cpue source / comments n kg n kg n kg n kg Solomon 5 4.0* Prescott:avg. of Islands 100 fishing trips catches by local fishermen 0 v o O i- l Kiribati 12 * * Prescott:single night 32 catches 40 C M 32

Christmas 358 1 .4** 321 1.5** Hoogesteger:catches Island 202 1 .6** 165 1.8** by local fishermen 269 1 .4** 458 1.5** 444 2 . 1** 116 1 .7**

PNG 10 2.3** Prescott:single night 14 3.1** catches 26 5.8** 15 3.3** 48 8.0**

Tonga 3285 15.0* Zann: catches by local 9493 8.3* fishermen. May not 617 6.2** have all been on dark 102 2.8** nights. 402 2.8** 200 8.9**

Enewetak 369 2.7** Ebert and Ford: average of 16 nights

* catch per night ** catch per man hour SPC/INSHORE FISH.RES./WP.18 Page 17

ECONOMICS

The international market demand for lobster is stong. From 1979 to 1984 world lobster exports increased in volume almost 30 percent to 44,000 tonnes, and a value of 511 million US dollars (Samples and Gates 1987). In the United States total consumption increased by 25 percent in the seven years to 1985 and reached a total of 57,000 t, of which 60 percent was imported (Samples and Gates 1987). During the same time period, spiny lobster real price remained relatively flat in the United States (Samples and Gates 1987), indicating increased demand, Figure 11. The major exporting and importing countries are shown in Figure 12.

Australia is the single largest exporter of spiny lobster and sets the market standard. Prices paid for Australian and New Zealand lobster products are significantly higher than lobster products originating in tropical countries, Table 6. Higher prices for the Australian and New Zealand lobster product is a result of a percieved higher quality of the cold water species, and importantly a higher quality partially due to better product handling (Samples and Gates 1987). This is certainly one area that South Pacific Island nations must address and endeavour to maintain high quality export products. In this regard, a regional body could be useful to help set and maintain standards on a regional basis, as poor quality in one country in the region may adversely affect prices realised by its neighbors.

Table 6. Average U.S. wholesale prices for frozen spiny lobster tails for the period of July 1985 to January 1987 by size and origin (a)

ORIGIN Tail size U.S. Dollars per Kilogram (ounces) Australia New Zealand Brazil Caribbean India Sri Lanka

<1 b b b b 5.05 b 2-4 b b 20.04 b 10.10 11.82 4-6 29.59 29.34 22.60 19.27 14.37 16.36 6-8 27.54 27.38 22.24 19.47 14.56 16.05 8-10 27.38 26.59 21.34 19.29 14.11 15.43 10-12 25.87 24.98 20.35 19.11 13.36 15.12 12-16 25.09 24.93 19.89 19.00 13.16 14.84 16-20 24.25 24.18 b 18.87 13.25 14.66 >20 23.28 23.06 b 18.87 13.73 14.62

Notes : (a) All prices quoted are wholesaler quotes with the exption of prices for India which are CIF, U.S. Port of entry. (b) No sales in this size category reported

Source : INFOFISH Trade News, INFOFISH, Kuala Lumpur, Malaysia 13/85-1/87, in Samples and Gates (1987) (prices converted to kilograms). SPC/INSHORE FISH.RES./WP.18 Page 18

Exports of lobster tails from Papua New Guinea primarily went to the United States and Australia during 1986 and 1987. Exports were almost exclusively P. ornatus from Torres Strait and Yule Island. Export prices to the United States were almost always higher than those to Australia, Table 7. While the Papua New Guinea export prices never exceeded K17.80 (approximately $ 19.70 US) fishermen in the Australian area of Torres Strait were being paid from approximately 17.75 to 21.00 US dollars per kilogram ex vessel for lobster tails of similar size and quality. Thus Papua New Guinea must be losing out on valuable export revenues. Possible explanations are the reputation of PNG lobster or simply the fact that Papua New Guinea is a developing nation and is thought to be producing a lower quality product, or export values are being falsified.

Table 7. The destination, minimum, maximum and mean export prices are shown for lobster tails (P. ornatus) exported from Papua New Guinea in 1986 and 1987 are shown in PNG Kina.

Year Destination Minimum Maximum Average Price Price Price

1986 Australia 13.00 15.00 13.99 USA 13.03 17.54 14.14 Singapore 13.00*

1987 Australia 12.00 17.80 14.20 USA 12.50 16.90 15.76

* one shipment only

Prices paid to fishermen for lobster tails have increased sharply in the Torres Strait area as competition between buyers has intensified. Fishermen are now paid from 6.00 to 10.50 PNG Kina per kilogram in the Torres Strait and Yule Island areas depending on whether the lobster is landed to a shore based facility of bought on the reef. Individual fishermen in Torres Straits may earn as much as 400 kina per day. Elsewhere in PNG where catches ar smaller and principally for domestic consumption prices vary from 2.00 to 3.50 PNG Kina per kilogram for whole lobster.

Despite a favourable international market situation, and high prices the author is aware of few examples of sustained lobster fisheries in the SPC area. One must therefore conclude that the economics of lobster fishing in the tropical Pacific are not favourable in most cases. Poor economic results are attributable to several important factors. The single most important factor is the size of the resource in a given area. Resource surveys by fishermen or scientists from outside the region may lead to overly optomistic predictions of catch. There is little published data on population size, growth and mortality for them to refer to. The water in most cases is clear and visual surveys, in particular for P. penicillatus may indicate a high abundance if the restricted size of the habitat is not taken into consideration. Initial catches can be high and if a unexploited area is fished for the first time or after a rest period of several years. SPC/INSHORE FISH.RES./WP.18 Page 19

However, once the initial high biomass has been reduced, subsequent catches will be sustained by recruitment and growth.

As discussed above, the sustained yield to a fishery for P. penicillatus is not high. It is suggested here that this situation may explain decline of the fishery for P. penicillatus in Tonga from the 1960's, and that lobster there were not overfished in the classical sense, as was generally believed.

Overly optomistic predictions usually lead to over-capitalisation, an unprofitable fishery and the eventual collapse of the operation. In most cases the cost of large, expensive collection vessels and processing facilities are unwarranted and not cost effective unless costs are partially offset by other marine products such as shellfish, Beche de Mer, or finfish.

MANAGEMENT

At the present stage of development in most parts of the Pacific restrictive management, in fisheries primarily for P. penicillatus. that may take the form of closed seasons, minimum size limits, or prohibitions on the taking of berried females seem to be unwarranted from a biological point of view. Studies of this species over a considerable range of its distribution indicate that the mean size at maturity is at or below the size of recruitment into a lamp or dive fishery. Consequently a significant component of the populations' reproductive potential is effectively protected. Furthermore, throughout much of the species distribution there are isolated reefs which remain unfished due to their remoteness or the lack of a market. Lobster larvae are able to control there dispersion to some extent by taking advantage of various currents at different depths, however, the long planktonic life virtually ensures that the dispersal will be wide. This is supported by the exceptionally wide distribution of this species and the presence of their larvae in samples taken far from the likely point of origin.

If yield per recruit curves are correct for the populations at Enewetak and the Solomon Islands, then lobster cannot feasilbly be overfished in terms of growth overfishing. Both analyses showed that the maximum yield per recruit were not achieved until levels of fishing mortality were quite high. To achieve these levels of fishing mortality, the amount fishing effort required is exceedingly high and unprofitable by virtually any standard. Restrictive minimum size limits, that is size limits greater than the length at recruitment, depress the yield per recruit curves at all realistic levels of fishing mortality, in the Solomon Islands and Enewetak. The populations studied at Enewetak and the Solomon Islands are considered to be representative of populations found over most of the SPC area. This may not apply to populations in higher latitudes such as Tonga. SPC/INSHORE FISH.RES./WP.18 Page 20

Closed seasons appear to have no biological justification. It has been shown that P. penicillatus breeds continuously over most of its range in the SPC area, therefore lobster cannot be protected during the breeding season as other species are in temperate waters where breeding is seasonal. Some degree of protection is offered however the same comments apply here that applied above. A case for closed seasons could be made on economic grounds. "Pulse fishing" for this species may be best for both fisherman and exporter. Allowing the stocks time to recover from previous fishing operations means catch per unit effort to improve for the fisherman which is likely to have a significant impact on the economics of his operation. There may be additional benefits for the exporter if catches are made over a short period of time so that storage costs and risks are minimised. The best possible way of ensuring that such a system worked would be by having a rotating closed season around various parts of a country, having consideration for climatic, social and, economic factors such as periods of high demand etc.

While few if any fisheries regulations may be justified from a stock conservation point of view in most countries, a note of caution should be made. Some countries may need to look more closely at conservation of the lobster stocks than others. In particular these are countries, or parts of countries where there may be less recruitment from outside. Relatively isolated areas probably recieve a much higher proportion of the post larval recruits from the reproductive output of resident lobster. It is fare to say, however, that the recruitment process is poorly understood in many large fisheries such as that for P. argus in the Atlantic where human and financial resources to carry out the required studies are less of a constraint. It is therefore unlikely that sufficient resources will be available for a study capable of answering these questions for a species with far less commercial importance.

STUDY METHODS

Tagging studies of P. penicillatus in the Solomon Islands proved difficult because of problems of having tags remain visible. Experience there showed that lobster apparently 'groomed' each other and in the process removed the external parts of the Western Australian rock lobster tags (Chittleborough 1974) that were used. It was uncommon for a tag to remain intact for more than a month and the external streamer was frequently entirely gone in period of two weeks. Tags remained visible only by the presence of the polypropylene filiment that became progressevely shorter with time, and in extreme cases by the presence of an opaque area visible when lobster were held before a light. The opaque area consisted of scar tissue surrounding the interal toggle part of the tag. Unfortunately, in most cases positive identification required that the lobster be killed to remove the internal part of the tag. SPC/INSHORE FISH.RES./WP.18 Page 21

Future tagging studies should use two marks, including a tag with a numbered or coded internal anchor and an external streamer, and a secondary mark made by coded punching of the telson and uropods. By double marking the lobster an estimate can be made of tag loss over several moults, and recaptures can be indentified to the period they were marked for multiple census methods of estimating population size even if the primary tag has disappeared. It may also allow the release of lobster that have not moulted between mark and recapture but have lost the external part of a tag, and increase the chance of obtaining useful growth data from the lobster later.

Because of the lobsters' nocturnal habits the biologist must modify his behavior pattern to coicide with the lobsters'. Except for P. ornatus all of the common species in the SPC area are most easily caught at night. Lobster can be picked up by hand while they forage over the reef flat without causing lobster to autolyse legs or antennae. During the day lobster usually must be pulled from their dens, in which case lobster are frequently damaged, resulting in stress and adding further to the possibility of abnormal growth patterns. Handling the lobster is best done at night to avoid or minimise the adverse affects of the sun, including damage to the eyes that leads to reduced chances of survival through loss of visual sensitivity (Meyer-Rochow and Tiang 1981) .

Surveys for P. penicillatus can be carried out by diving or walking the reef flats, however in most situations where the two methods have been used together the divers' catch per unit effort has usually been higher. Furthermore, the biologist is able to assess the quality of the of the habitat directly. Divers are also able to cover the complete range of the habitat and make observations of the lobsters' behavior. The habitat is not easy for divers or reef walkers to work in and surveys may often be delayed due to rough sea conditions.

The catch per unit effort by either method should be a reasonable index of lobster abundance once a survey team has reached a stable level of proficiency. However, records should be kept for environmental variables such as sea state, visibilty, tide, and lunar phase as each may affect CPUE. Correction factors for catch per unit effort may be warranted if the population density of the reference population is significantly different than the population being sampled, since search time is lost to handling time when catches increase. In some areas this could lead to a significant underestimate of population size. Correction factors could be determined by using visual counts without capture in conjunction with normal capture surveys. In areas that are heavily fished catchability may reduced due to a behavioral change in the lobsters where they become more wary of divers and evade capture by any early escape response. The author has observed such changes in escape responses during the course of the mark- recapture study in the Solomon Islands that led to the lobster becoming much harder to catch. SPC/INSHORE FISH.RES./WP.18 Page 22

Intensive fishing experiments on discreet reefs similar to those done by Ebert and Ford (1986) can be an effective way to get relatively rapid estimates of population size and catchability using Leslie or DeLury, for example. If the natural mortality rate (M)is known or can be resonably approximated, rough estimates of maximum yield can be obtained by using the formula :

where BQ is the initial biomass which can be obtained by the estimates of initial numbers and the average weight of the catch, and a is a factor of between 0.3 and 0.5 (Gulland 1983). It would appear from data presented by Morgan (1980) that a factor of 0.3 may even be high for P. cvgnus in Western Australia.

SUMMARY

Three genera of spiny lobster are found in the SPC area. Two of these, Justitia and Puerulus, are uncommon and have no commercial importance. The third genus, Panulirus, is the most diverse with six species, and is numerically dominant. Panulirus penicillatus has the widest distribution of any spiny lobster and is found in all countries in the SPC area. This species presently supports artisanal and small scale commercial fisheries at various points in its wide distribution. In Papua New Guinea and Australia P. ornatus supports a commercial fishery with annual catches averaging in excess of 350 tonnes tail weight annually.

Throughout the SPC area all species appear to breed continuously during the year except P. ornatus which makes a unique breeding migration of 500 kilometres once during its life in Papua New Guinea. The mean size at maturity for P. penicillatus appears to be from 75 to 80 millimetres carapace in each of the localities where it has so far been studied. It appears that the number of broods the female carries per year increases to a maximum of more than ten as they grow, but begins to decline as they approach their maximum size. Batch fecundity is related to carapace length in a linear manner in both Tonga and the Solomon Islands. In the Solomon Islands mean size at maturity is below the size of recruitment and a substantial component of the populations' reproductive capacity is essentially safe from fishermen at realistic levels of effort. Despite the high reproductive output of the species it is thought that in most cases lobster populations are probably recruitment limited.

The growth rate of P. penicillatus is faster than many of the colder water relatives. Males grow more rapidly than females and are fully recruited to the fishery at a larger size and an age of three years, which is the same for females, in the Solomon Islands. The growth rate followed the same pattern at Enewetak in Micronesia. SPC/INSHORE FISH.RES./WP.18 Page 21

SUMMARY

Estimates of natural mortality vary from 0.24 to 0.43 between Enewetak and the Solomon Islands. Using the estimate for natural mortality, population size and the growth parameters of the von Bertalanffy growth equation yield per recruit and total yield were made for several reefs at Enewetak. The estimated average annual yield for the three reefs with moderate levels of fishing (F=.5) was approximately 1000 kilograms, or about 20 to 30 kilograms per kilometre of reef edge. One important feature of the yield per recruit curves is that the yield per recruit does not decline until high levels of fishing mortality are reached. In the Solomon Islands yield per recruit analysis indicates that minimum size restrictions would actually reduce yield per recruit.

Records of lobster landings are difficult to find for the SPC area and those that have been collected in many cases may fail to adequately represent the full extent of the lobster landings. Catch and effort data is available for a number of localities in the SPC area but is reported in various units of catch and effort. Catch rates generally vary from about 1.5 to 8.0 kilograms whole weight per man hour.

Despite favourable international market conditions, there are few examples of sustained lobster fisheries in the SPC area. It is suggested that this is the result of limited lobster resources that are frequently over estimated by fishermen and entrepreneurs that are unfamiliar with potential yields. There may be little requirement for management to conserve the stocks due to the small size of maturity and relatively large size at recruitment and the fact that there are at present many remote refuges that continue to produce recruits. However, management may be required to maximise returns to the fishermen and allow a profitable collection and marketing infrastructure. It is suggested that a system of rotating closed seasons around a country would allow stocks to recover following short lived but intense fishing pressure. Catch per unit effort can be maintained at profitable levels, and total catches are large enough to warrant the cost of the infrastructure required to market the product, by such a management scheme. SPC/INSHORE FISH.RES./WP.18 Page 24

Beverton, R.J.H. and S.J. Holt, 1956. A review of methods for estimating mortality rates in exploited fish populations, with special reference to sources of bias in catch sampling. Rapp. P.-V. Reun. Cons. perm. Explor. Mer. 140:67-83.

Beverton, R.J.H. and S.J. Holt, 1957. On the dynamics of exploited fish populations. Fishery Invest., London, Ser. 2, 19. 533 pp.

Beverton, R.J.H. and S.J. Holt, 1969. Tables of yield functions for fishery assessment. FAO Fish. Tech. Pap., No. 38:49pp.

Briones, P. and E. Lozano, 1982. Nuevas localidades en la distribucion de Panulirus penicillutus (Oliver) y P. inflatus (Bouvier) en Mexico. (Crustacea:Decapoda : Palnuridae). An. Inst. Cienc. del Mar y limnol. Univ. Nal. Auton. Mexico, 9(1):389-384.

Chittleborough, R. G., 1974. Development of a tag for the western rock lobster. Commonwlt. Sci. Ind. Res. Org.(Aust.), Div. Fish. Oceanogr. Rept. 56:1-9. Ebert, T.A. and R.F. Ford, 1986. Population Ecology and fishery potential of the spiny lobster Panulirus penicillatus at Enewetak Atoll, Marshall Islands. Bull. Mar. Sci., 38(l):56-67.

George, R.W., 1972. South Pacific Islands Rep. S. Pac. Is. Fish. Dev. Agency Rome. UN/FAO 1-42.

George, R.W., 1974. Coral reef and rock lobster ecology in the Indo-west Pacific region. Proc. Int. Coral Reef Symp. 2nd. 1974, Vol.1, 321-325.

Gordon, I., 1960. The genus Justitia (Holthuis) (Decapoda, Palinuridae), with a note on alltometric growth in Panulirus ornatus (Fabricus). Crustaceana. l(4):295-306.

Grey, K.A. , 1979. Estimates of size at first maturity of the western rock lobster, Panulirus cygnus. using secondary sexual characteristics. Aust. J. Mar. Freshw. res. 30:785-791.

Gulland, J. A., 1969. Manual of methods for fish stock assessment, Part 1. Fish population analysis. FAO manuals in fisheries science No. 4. Rome.

Gulland, J.A., 1983. FAO/Wiley Series on food and agriculture. Fish stock assessment: Vol.1, a manual of basic methods. John Wiley and Sons, Chichester.

Hoogesteger, J., A report on the lobster export fishery of Christmas Island, January to June 1980. Unpublished report. 16pp. SPC/INSHORE FISH.RES./WP.18 Page 25

Johnson, M.W., 1974. On the dispersal of lobster larvae into the east Pacific barrier (Decapoda, Palinuridae). Fish Bull. 73, 639-647.

Jolly, G.M., 1965. Explicit estimates from capture-recapture data with both death and immigration - stochastic model. Biometrika, 52: 225-247.

Juinio, A.R. and E.D. Gomez, 1986. Spiny lobster fishery in Eastern Samar, Philippines, P. 381-384. In J.L. Maclean, L.B. Dizon, and L.V. Hosillos (eds.) The first Asian Fisheries Forum. Asia Fisheries Society, Manila, Philippines.

MacDonald,C.D., 1982. Catch composition and reproduction of the spiny lobster. Panulirus versicolor at Palau. Trans. Am. Fish. Soc. 111:694-699.

MacFarlane, J. W. , and R. Moore, 1985. Reproduction of the ornate rock lobster. Panulirus ornatus (Fabricus), in Papua New Guinea. Aust. J. Mar. Freshw. Res. 37 (1):55-66.

Mauchline, J., 1977. Growth of shrimps, crabs and lobsters - an assessment. J. Cons., cons. Int. Explor. Mer. 37(2):121-131.

McGinnis, F., 1972. Management investigation of two species of spiny lobsters Panulirus j aponicus and P . penicillatus, division of Fish and Game Report, Department of Land and Natural Resources, Honolulu, 47pp.

Meyer-Rochow and Tiang, 1981. Seeing lobster are correctly treated. Catch '81. April:17-20. Moore, R. and J.W. MacFarlane, 1984. Migration of the ornate rock lobster, Panuliurs ornatus (Fabricus). in Papua New Guinea. Austr. J. Mar. freshw. Res. 35, 197-212.

Morgan, G.R., 1980. Population dynamics of spiny lobsters. Chapter 5 in: The biology and management of lobsters, Cobb, J.s., and B.F. Phillips (eds.), vol.11, Academic Press, N.Y.

Morris, D.E., 1968. Some aspects of the commercial fishery and biology of two species of spiny lobster, Panuliurs j aponicus (De Siebold) and Panulirus penicillatus (Oliver), in Hawaii. M.S. Thesis, University of Hawaii, Honolulu. 82 pp. SPC/INSHORE FISH.RES./WP.18 Page 26

Munro, J.L., 1974. The biology, ecology, exploitation, and management of Caribbean reef fishes. Scientific Report of the ODA/UNI fisheries ecology research project, 1962-1973. Part VI. The biology, ecology and bionomics of Caribbean reef fishes - Crustaceans (Spiny lobsters and crabs). Univ. West Indies Zool. Dep., Res. Rep. 3, 1-57.

Peacock, N.A., 1974. A study of the Spiny lobster fishery of Antigua and Barbuda. Proc. Gulf carbb. Fish. Inst. 26:117-130.

Phillips, B.F.; P.A. Brown; D.W. Rimmer; and D.D. Reid, 1979. distribution and dispersal of the phyllosoma larvae of the western rock lobster, Panulirus cygnus. in the South-eastern Indian Ocean. Aust. J. Mar. Freshw. Res. 30:773-783.

Phillips, B.F. and P.S. McWilliam, 1986. the pelagic phase of spiny lobster development. J. Fish. Res. Board Can. 43(ii):2153-2163.

Phillips, B.F., and L. Olsen, 1975. Swimming behaviour of the Puerulus stage of the Western rock lobster. Aust. J. Mar. Freshw. Res. 26(3): 415-417.

Phillips, B.F. and A.N. Sastry, 1980. Larval Ecology Chapter 1 in: The biology and management of lobsters, Cobb, J.S. and Phillips, B.F., (eds.), Vol.11, Academic Press, N.Y. Prescott, J.H. Report on the Biology of P^. penicillaus in the Solomon Islands. Unpublished report.

Samples, K.C. and P. Gates, 1987. Market Situation and outlook for Northwestern Hawaiian Islands spiny and slipper lobsters. National Marine Fisheries Service Southwest Fisheries Centre Administrative report, H-87-4C, Honolulu, Hawaii.

Shaklee, J.B., 1983. Mannosephosphate Isomerase in the Hawaiian spiny lobster, Panulirus morginatus: a polymorphic, sex-linked locus useful in investigating embryonic and larval sex ratios. Mar. Biol. 73:193-201. von Bertalanffy, L., 1938. A quantitative theory of organic growth. Hum. Biol. 10(2):181-213.

Zann, L.P., 1984. A preliminary investigation of the biology an fisheries of the spiny lobsters (Palinuridae) in the Kingdom of Tonga. Institute of Marine Resources, University of the South Pacific Report, 55pp. SPC/Inshore Fish. Res./WP.18 Page 27

PERCENT OVIGEROUS LOBSTER BY SIZE IN THE SOLOMON ISLANDS AND TONGA 70/)

eojo -

BOX) -

) 40J0 -

300 -

200 -

KKO

CARAPACE LENGTH SOLOMON IS + TONGA

Figure 1. The percentage of ovigerous female P. penicillatus in 5mm carapace length size intervals is plotted for the Solomon Islands and Tonga (from Zann 1984). SPC/Inshore Fish. Res./WP.18 Page 28

PERCENT OVIGEROUS FEMALES BY MONTH

MONTH

Figure 2. Percentage of all females carrying eggs in monthly samples of P. penicillatus from the Solomon Islands is shown for combined months from September 1975 to October 1977. SPC/Inshore Fish. Res./WP.18 Page 29

FECUNDITY OF P. PENICILLATUS IN THE SOLOMON ISLANDS AND TONOA 600

TOO -

OOO -

BOO -

-400 -

300 -

200 -

100 -

OOJOO TOOO OOJOO 100J00

CARAPACE LENGTH 13. TONOA

Figure 3. Regression lines of batch fecundity on carapace length are shown for samples from P. penicillatus in the Solomon Islands and Tonga (source Zann 1984). SPC/Inshore Fish. Res./WP.18 Page 30

RELATIVE IMPORTANCE OF SIZE INTERVALS TO TOTAL REPRODUCTIVE OUTPUT

I 5

CARAPACE LENGTH Figure 4. The estimated relative reproductive output (eggs) made by lobster in various size intervals corresponding to age in years from age 2+ is plotted. The plot was made using the batch fecundity, the estimated number of broods per year, and a hypothetical age and size ditribution of the population based on an annual natural mortality rate of 0.43. SPC/Inshore Fish. Res./WP.28 Page 31 Solomon Islands

KO-

120 •

100-

80-

T 6 8 10 12 U 16 18

O) Figure 5a. Growth curves are shown for male and female P_j. c penicillatus from the Solomon Islands. Enewetak 4) U a 140* (0 (0 U 120

100-

80-

60-

40-

20-

Age (years)

Figur 5b. Growth curves are shown for male and female P. penicillatus from Enewetak (redrawn from Ebert and Ford 1986) .

. :'(.i Inshore Fish. Res./WP.18 Page 32

CONFUCI ISLANDS ENEWETAK

n \ \ •j 1

1 1 1 n'

h R

\ n n

cans nam O«"o Oraaa EZI an S3

SOLOMON ISLANDS TONGA SPC/Inshore Fish, Res./WP.18 Page 33

AVERAGE TAIL WEIGHT OF P. ORNATUS IN TOMES arrrtvr nsHEfrr

Figure 7. Average montly tail weights of P. ornatus landed at Daru, PNG, by divers are shown plotted from January 1983 to December 1986. ^^ RER UN|y EFpoRT

IN rotwca arrnArr riaHEPsr 4A

JAN MAY aEP JAN MAY SEP JAN MAY SEP JAN MAY SEP Figure 8. Mean monthly catch per unit effort (kg tails per man day) of the divers fishing in Torres Strait from Daru are plotted from January 1983 to December 1986. TOTAL LANDINGS TO DARU rnoM romRca STPJVT riaHEivr TJOO

OJOO -

4JOO -

3JOO

SJOO -

uoo I • ' • I JAN MAY SEP JAN MAY tEP JAN MAY_ aEP '*986a 1983 ftdn^^rf -C,'i

YIELD PER RECRUIT IN THE SOLOMON ISLANDS

-[—i—i—i—i 1—r 2J00 OJDO 0£Q 0.40 OJOO COEFFICIENT OF FISHINO UOPCrAlirf (F) — — FEMALES MALES Figure 10. The proportional yield per recruit (Y'/R) curves are shown for male and female P. penicillatus in the Solomon Islands. SPC/Inshore Fish. Res./WP.18 Page 35

U.S. AVERAGE ANNUAL IMPORT PRICES IN REAL DOLLARS FROU1070-1066

w '/ V, -// P I P / / // I '/. V /. / 8 A I// ^ '/AS. *-/, /. I A k2£2 ^ 2^ (Z\ •A$ 1070 1060 ioa 1062 7083 1064 1065 CALENDAR YEAR V7\ SPINY LOBSTER [VSJ CLAWED LOBSTER

Figure 11. The average U.S. import price of spiny and clawed lobster is shown for 1979 to 1985. Prices are quoted in 1985 (CPI) adjusted U.S. dollars per Kilogram. Source: U. S. Department of Commerce, National Marine Fisheries Service, Current Fisheries Statistics No. 8380 (April 1986), Fisheries of the United States: 1985 Washington D.C. (and previous issues)., in Samples and Gates 1987. SPC/Isnhiore Fish. res./WP.18 Page 36

MAJOR EXPORTING COUNTRIES IN REAL DOLLARS FROU 1070-1080

OTHERS (20X390

CANADA (00X390

HONDURAS OJOm

BRAZIL (OJO%)

NEW ZEALAND (OJMi

SOUTH AFRICA MJOMt AUSTRALIA (17X390

MAJOR IMPORTING COUNTRIES IN REAL DOLLARS FROU 1079-1000

OTHERS (4XHO

FRANCE (13X390

CANADA OLOM

NETHERLANDS (1X390

JAPAN (MX390 USA (63X310

Figure 12. Major exporting an importing countries of edible lobster products in 1984. Source: U. S. Department of Commerce, National Marine Fisheries Service, Current Fisheries Statistics No. 8380 (April 1986), Fisheries of the United States: 1985 Washington D. C. (and previous issues)., in Samples and Gates 1987.