Biological reproduction variables of scalloped spiny lobster ( Panulirus homarus Linnaeus, 1758) in the west coast of Lampung province

. The scalloped spiny lobster ( Panulirus homarus ) is one of the dominant lobster species caught by fishermen in the west coast of Lampung Province. The spiny lobster fishing seems to be high pressure due to the catch result having a reasonable price for domestic and export market. However, little information on the biology of this species in the west coast of Lampung Province is considered for management. This study aimed to analyze the biological reproduction variable of scalloped spiny lobster, i.e., sex ratio, length-weight relationship and relative condition factor, maturity, reproductive potential, and spawning type. The sample was collected by simple random sampling method on the main holding center from October 2021 to March 2022. Results showed that the caught of P. homarus carapace length was in the range of 41-94 mm, the sex ratio was about 1:1.12, there was a negative allometric growth pattern for both sexes, the condition factor, and the gonadosomatic index tended to be increased from October to December, and then decrease. Gonad with fully mature stage ( stage III ) was found every month for both sexes, and the peak of spawning season occurs in November-December. Fecundity as the reproductive potential of P. homarus was in the range of 762-182,000 eggs, while size at onset maturity or mean size of first spawning was at 63.10 mm carapace length. Spawning patterns tend to be partial spawners. Females of P. homarus below the size at onset maturity are often caught. It is recommended to this fishery that minimum legal size should be applied in the carapace length greater than 64 mm. Keywords


Introduction
Spiny lobster (Panulirus spp.) is an economically essential crustacean species in Indonesia due to the catch result having a good price for the domestic and export markets.There are at least seven lobster species can be found in Indonesian waters, i.e., scalloped spiny lobster (P.homarus), pronghorn spiny lobster (P.penicillatus), ornate spiny lobster (P.ornatus), painted spiny lobster (P.versicolor), longlegged spiny lobster (P.longipes longipes), stripeleg spiny lobster (P.femoristriga), and mud spiny lobster (P.polyphagus) [1].All species have been caught by the fisher in almost all its distribution areas, including in the Indonesian Fisheries Management Area (IFMA) 572 or part of the Indian Ocean in western Sumatera.
The potential of lobster resources in IFMA 572 is high, as well as the level of its utilization [2].The dominant lobster species obtained in this area included the scalloped spiny lobster (P.homarus).The waters of the west coast of Lampung Province are part of IFMA 752 and have a high potential for lobster resources.This area is also one of the main location for lobster trading transactions in Indonesia [3].However, the scalloped spiny lobster is not a species with high dominating potential in this area but has high selling value.In the international market, the selling price of lobsters, including scalloped spiny lobsters, ranges from US$ 50-80 per kilogram for individual sizes of 300 grams to 1 kilogram and US$ 100 per kilogram for sizes more than 1 kilogram [4].
Fishing intensity of lobsters in general and scalloped spiny lobsters in particular, using gill net fishing gear on the west coast of Lampung, is indicated to be high.Intensive lobster catching can affect the balance and existence of lobster stocks in nature, causing a decrease in stocks, an imbalance in the sex ratio of lobsters, to the extinction of species [5].Due to such consequences, there is a need for efforts to manage the existence of lobster resources based on scientific evidence.
Research on the biology, ecology, population dynamic, and fishery of scalloped spiny lobster has been carried out in some Indonesian waters [6,7,8,9,10,11], especially in West Aceh as part of the IFMA 572 [12].However, there is little information on the biology of this species on the west coast of Lampung Province, even though this area is part of IFMA 572.The scalloped spiny lobster population on the west coast of Lampung Province might be one stock unit in the IFMA 572 or not.Therefore, in maintaining the sustainable use of lobster resources in the west coast of Lampung waters, management efforts are needed.Management efforts that are applied need to be adjusted to the biological aspects of certain lobster species that exist in this area.Scalloped spiny lobster is one of the dominant species caught in the waters of the west coast of Lampung.It is necessary to study the reproductive biology of this species as a basis for resource management so that the sustainability of this lobster population is maintained and provides long-term community benefits.This study's purpose was to analyze the biological reproduction variables of scalloped spiny lobster, i.e. sex ratio, lengthweight relationship and condition factor, maturity, gonadosomatic index, reproductive potential, and size at onset of maturity or mean size at first spawning in the west coast waters of Lampung Province.

Data collection
Monthly sampling was made in the main holding center of caught spiny lobster at Krui Subdistrict, West Coast District of Lampung Province (Fig. 1) from October 2021 to March 2022.Lobsters from the landing site of the gill-net fishery in the Southeastern and Northwestern areas were brought for live packing to the main holding center in Krui, where Krui is also the center of the interregional market.Scalloped spiny lobster samples were taken by random sampling method.The data collected included sex, carapace length (CL), total weight (W), gonad weight, gonadal maturity level, fecundity, and condition of the gonads in females carrying eggs or berried females.The sex of the scalloped spiny lobster was observed visually based on the differences in the characteristics of the genitalia (gonopore), tip of the fifth prong, and ovigerous setae on the swimming legs (pleopod).Male lobsters have an oval gonopore at the base of the fifth pereopod, and the tip of the fifth proboscis has no pseudo-claws and no ovigerous setae.Meanwhile, female lobsters have a rounded gonopore at the base of the third pereopod, the tip of the fifth leg has pseudo claws and ovigerous setae on the pleopod [13].Quantifying the carapace length (CL) of each sample was the distance from the rostral sinus to the posterior edge of the carapace to the nearest 0.1 mm using a Vernier caliper, as well as total length (TL) using measuring tape.Meanwhile, total weight (W) was measured using digital balance to the nearest 0.1 g in the field laboratory.
The lobster sample was dissected after quantifying its CL and W, followed by observation of the texture, color, and measured the testes and ovaries weight to the nearest 0.01 g using digital balance.Subsequently, testes and ovaries development were classified into four macroscopically stages based on [14,15], i.e., stage I = immature, stage II = maturing (prematuration), stage III = mature (mature extrusion), and stage IV = spawning (post extrusion).Egg bearing female samples were also dissected to observe their ovaries and determine their condition, such as above the development.Meanwhile, the fecundity of scalloped spiny lobsters in one spawning season was determined by counting the number of eggs that have been fertilized and attached to the ovigerous setae, where eggs or ovum with an orange or yellow color were only considered in measurement [16].The egg mass on the pleopods was removed from the female's abdomen and preserved with 70% ethanol, and then dried, sieved, and weighed to the nearest 0.001 g in the field laboratory.Subsequently, three 0.1 g subsamples were measured for their fecundity, and the average number of eggs was multiplied by the total weight of the egg mass to obtain the number of fecundity for an individual sample per spawning [17].

Data analysis
The sex ratio value is the ratio of male to female lobsters, and chi-square analysis was applied to test.The relationship between carapace length and total weight (LWR) was calculated using the equation from [18] and followed by the t-test of the b value obtained [19].Meanwhile, condition factors were analyzed for both sexes using the formula of [20].The gonadosomatic index (GSI) was calculated as gonad weight in g/body weight in g × 100.Size at onset maturity or spawning was measured based on the length of the egg bearing females and it was analyzed using the Spearman-Karber method [21].

Results and Discussion
Scalloped spiny lobsters (P.homarus) caught on the west coast of Lampung Province waters during the study period had carapace lengths (CL) from 41 to 93 mm.Male lobsters size ranges from 42 to 81 mm CL, while females size from 41 to 93 mm CL.The dominant spiny lobster caught was in the size class of 53-58 mm CL.This lobster size tends to be larger than the scalloped spiny lobster caught in the southern part of Java, i.e., in Yogyakarta and Pacitan which, the size between 28.2 to 85.2 mm CL [7] and Palabuhanratu Bay with the size between 27 to 69 mm CL [11].However, this size is smaller or smaller range than in Tabanan-Bali, with the size of about 36.00 to 105.6 mm CL [8] and West Aceh waters with a size between 39.0 to 112.0 mm CL [12].
The sex ratio of the P. homarus obtained was generally 1:1.12 and, based on the Chisquare test was relatively balanced or 1:1 (Table 1).The balanced proportion of male and female lobsters indicates that male and female lobsters have the same chance of being caught.The ideal sex ratio is when the population is in a balanced condition or the frequency of females is more than males, under such conditions the sustainability of the population will be maintained [22].The above condition is different from the results of research on scalloped spiny lobsters in the waters of Ekas Bay, Lombok Island [6] and in the waters of West Aceh [12], where female P. homarus predominate.However, the sex ratio can change over time, due to the influence of an increased mortality rate and a decreased growth rate [23].Carapace length (CL) to body weight (W) relationships in P. homarus captured on the west coast of Lampung waters were W = 0.3674 CL 1,426 for males and W = 0.4066 CL 1,4479  for females (Fig. 2).Based on the t-test applied to b value, both male and female spiny lobsters had a negative allometric growth pattern or hypoallometric (b<3) and there was no significant difference (p>0.05) of the regression coefficients between male and female lobsters.This result indicated that male and female lobsters have similar gains in length and weight growth.Several research results in other regions in Indonesia (i.e., Yogyakarta, Bali, and Sorong) also show the same growth pattern [7,8,23].The same growth pattern in different areas can be caused by the similar characteristics of the waters in supporting the availability of food and suitable habitat for lobsters.The mean condition factor tends to increase from October to December for both males and females and then decrease.The highest condition factor for male scalloped spiny lobster was 1.21 and was found in November, while for female spiny lobster it was 1.48 in December (Fig. 3).Condition factors that vary temporally indicate the influence of the reproductive period.The condition factor for female lobsters increased in the November and December periods thought to have occurred because of spiny lobsters in the spawning period.After the spawning season, condition factor values decreased (January-March).This is supported by the increasing number of female spiny lobsters with GMS IV and berried females.Testes and ovaries development of scalloped spiny lobster were found such as in Fig. 4, while the temporal distribution of gonad development seem to show slight variation between male and female.Gonads with the fully mature stage (stage III) were found every month for both sexes and the percentage of male spiny lobsters that have mature gonad (GMS III) dominated from October 2021 to March 2022 (Fig. 5).The same thing was also found in female spiny lobsters, where the percentage of females with GMS III was relatively high every month, especially during November to December.Both male and female with the GMS IV tend to be increase from November to January/February which indicate the high occurrence of spawning.
The average value of the gonadal maturity index (GSI) for male scalloped spiny lobsters is in the range of 1.06-1.34while the average GSI for female scalloped spiny lobsters is in the range of 0.74-1.89(Fig. 6).The highest value of the gonad maturity index for male scalloped spiny lobsters was in October, while for females in December.The peak of the spawning season during the observation period seems to be occurred in November-December.December period coincides with the rainy season and the west monsoon.During the rainy season, high rainfall will decrease the salinity of the coastal water, so that spiny lobsters are encouraged to come out of the reef and look for partners to breed [25].

Male Gonad
Female Gonad  Berried female or egg-bearing females were frequently found with gonad in maturity stage III, indicating that the spawning pattern tend to be partial spawner (Fig. 7a).Meanwhile, the percentage of berried females with gonad in maturity stage IV were also high during November-December, which support the hypothesis related to the peak of spawning season.Fecundity as reproductive potential was in the range between 762-182,000 eggs per spawning.The fecundity of female P. homarus in several other areas, such as Bali, Lombok, and India, showed varying results [6,8,26].Female scalloped spiny lobsters are capable of producing 100,000-900,000 eggs in one incubation period (Chan, 1998).The differentiating factor on the number of eggs is influenced by several factors including nutrition related to the quantity and quality of food, variations in the size of female individuals, and the age and average size of the first spawning [27].
Size at onset maturity or mean size of first spawning at 63.10 mm CL (Fig. 7b).The size at onset maturity is smaller than that found in Ekas Bay-Lombok, which is 77.44 mm CL [6], and in Tabanan-Bali is at 68.52 mm CL [8].The size of the first sexual maturity correlated positively with the observed maximum size of sexually mature female lobsters [28], and it can vary according to time and growth rate.Geographically, variation in size at first sexual maturity can be influenced by environmental parameters such as temperature and food quality [29].During the observation period, males and females scalloped spiny lobsters smaller than the size at onset of spawning were often caught.It is recommended to this fishery that a minimum legal size should be applied in the carapace length greater than 64 mm for the sustainability of resources.It is slightly different from the Regulation of the Minister of Marine Affairs and Fisheries Number 16 of 2022 that the lobsters (P.homarus) allowed to be caught are more than 60 mm CL or individual weights above 150 grams.

Conclusion
The caught scalloped spiny lobsters have a balanced sex ratio and a negative allometric growth pattern.Spawning occurred during the observation period with a peak in November-December and the increasing condition factor and gonadosomatic index, and tend to be partially spawner.The average reproductive potential was high per spawning.Many female scalloped spiny lobsters are caught below the size at the onset of spawning, so this fishery should manage with the minimum legal size at the size at onset of spawning.

Fig. 1 .
Fig. 1.Map of research location on the west coast of Lampung Province, Indonesia.

Fig. 2 .
Fig. 2. Length-weight relationship of male and female scalloped spiny lobster on the west coast of Lampung Province.

Fig. 3 .
Fig. 3. Condition factors for male and female scalloped spiny lobsters (P.homarus)on the waters of the west coast of Lampung Province

Fig. 4 .
Fig. 4. Gonad maturity stage (GMS) of male and female scalloped spiny lobster on the west coast of Lampung Province.

Fig. 5 .
Fig. 5. Temporal distribution of gonad maturity stage (GMS) of male and female scalloped spiny lobster on the west coast of Lampung Province.

Fig. 6 .
Fig. 6.Gonadosomatic index (GSI) of male and female scalloped spiny lobster on the west coast of Lampung Province.

Fig. 7 .
Fig. 7. Temporal distribution of berried female with gonad maturity stage III and IV (a) and the size at onset spawning of scalloped spiny lobster (b) in the west coast of Lampung Province.

Table 1 .
Sex ratio of scalloped spiny lobster (P.homarus) on the west coast of Lampung Province.