ACTA ICHTHYOLOGICA ET PISCATORIA (2014) 44 (1): 75–84 DOI: 10.3750/AIP2014.44.1.10 RAPID REPRODUCTIVE ANALYSIS AND LENGTH–WEIGHT RELATION FOR RED-BELLIED FUSILIER, CAESIO CUNING, AND LONGFIN EMPEROR, LETHRINUS ERYTHROPTERUS (ACTINOPTERYGII: PERCIFORMES: CAESIONIDAE AND LETHRINIDAE) FROM A REMOTE VILLAGE IN PAPUA NEW GUINEA Ken LONGENECKER 1*, Ross LANGSTON 1, 2, Holly BOLICK 1, and Utula KONDIO 3 1 Department of Natural Sciences, Bishop Museum, Honolulu, Hawaii, USA 2 Department of Natural Sciences, Windward Community College, Kaneohe, Hawaii,SA U 3 Kamiali Wildlife Management Area, Lababia, Morobe Province, Papua New Guinea Longenecker K., Langston R., Bolick H., Kondio U. 2014. Rapid reproductive analysis and length–weight relation for red-bellied fusilier, Caesio cuning, and longfin emperor, Lethrinus erythropterus (Actinopterygii: Perciformes: Caesionidae and Lethrinidae) from a remote village in Papua New Guinea. Acta Ichthyol. Piscat. 44 (1): 75–84. Abstract. We present length–weight relat ions (LWR) and use rapid, low-cost histological methods to describe the reproductive biology of the red-bellied fusilier, Caesio cuning (Bloch, 1791), and the longfin emperor, Lethrinus erythropterus Valenciennes, 1830, based on 137 and 139 specimens, respectively, collected from 3.0322 a remote area in Papua New Guinea. The LWR for C. cuning is W = 0.0208FL . We estimate male L50 at 12.6 cm FL and female L50 at 15.3 cm FL. Overall sex ratio of mature individuals is not significantly different from 1 : 1; however, sex-ratio does vary with length. Females dominate size-classes from 17 through 20 cm and males are more abundant in smaller and larger size classes. The species is a batch-spawning gonochore. Batch fecundi- ty is an exponential function of length BF = 0.1163FL4.2796. The LWR for L. erythropterus is W = 0.0145FL3.0976 for all specimens, but the length–weight relation differs between sexes. We estimate minimum size-at-maturity for males at 19.2 cm FL, and female L50 at 20.4 cm FL. Overall sex ratio of mature individuals is not significant- ly different from 1 : 1; however sex-ratio does vary with length. Males dominate size classes > 21 cm. The species is a batch-spawning, protogynous hermaphrodite. Keywords: size-at-maturity, reproductive mode, gonadosomatic index, size-specific sex ratios, batch fecundity, Morobe Province One of the most easily understood concepts in fishery conservation (Dalzell 1998). The reason for the latter management and conservation is to harvest individuals problem may be as simple as a lack of basic infrastructure only after they have grown large enough to reproduce, thus (e.g., electrical service needed to operate laboratory allowing each generation to “seed” the next (Froese 2004). equipment) in many parts of these developing countries. However the concept is difficult to put into practice To address these issues, and as part of a larger marine- because basic reproductive information such as size at conservation effort (see Longenecker et al. 2013c), we maturity is lacking for ~83% of exploited species world- initiated a research program to generate reproductive wide (Froese and Binohlan 2000). This problem is espe- information for Pacific coral-reef fishes. We use recently cially intractable for coral-reef fishes; their sheer diversi- developed methods for rapid, low-cost, on-site, histology- ty, and the supposed cost associated with the reproductive based reproductive analysis that requires minimal analysis of each species are often cited as barriers to research infrastructure (Longenecker et al. 2013a, 2013b). obtaining this important information (Roberts and These methods use standard techniques (e.g., plastic Polunin 1993, Johannes 1998). Further, many Pacific embedding) that have been modified such that work can island nations, where many of the world’s coral reefs are be conducted in remote field settings without electrical located, have little or no capacity to conduct the reproduc- service. With these methods, reproductive information tive research needed to support fishery management and can be generated quickly and at low cost, thus eliminating * Correspondence: Dr. Ken Longenecker, Department of Natural Science, Bishop Museum, 1525 Bernice Street, Honolulu, HI, 96817, USA, phone: +1 808 847 8273, fax +1 808 847 8252, e-mail: (KL) [email protected], (RL) [email protected], (HB) [email protected]. 76 Longenecker et al. the perceived impediments to broad-scale reproductive The length–weight relation presented here may not be analysis of Pacific coral-reef fishes. However, in the inter- applicable throughout the range of the species. Caesio est of rapidly increasing the amount of available repro- cuning populations in the Coral Triangle represent three ductive information, we analyze only one gonad subsam- stocks, with significant limits to genetic exchange ple from the minimum number of specimens necessary to between individuals from New Guinea and those in generate estimates of reproductive parameters. Therefore, Pacific and Indian Ocean clades (Ackiss et al. 2013). results of rapid reproductive analysis should be viewed as Further, the maximum length of individuals at KWMA preliminary. appears to be smaller than the maximum reported length Our research program consists of annual, two-week of approximately 42 cm FL, derived by applying the field trips to the subsistence-fishing village of Lababia, TL–FL relation of Froese and Pauly (2013) to the maxi- Papua New Guinea (PNG), which holds traditional tenure mum total length of 50 cm (Carpenter 1988, Allen and over the waters of the Kamiali Wildlife Management Area Swainston 1993). The largest specimen in the presently (KWMA hereafter; Fig. 1). Each year, village residents reported study was 22.7 cm FL, whereas the largest pub- choose four study species, using the following criteria: lished length for C. cuning at KWMA is 31 cm FL • All are an important part of village fish catch; (Longenecker et al. 2013c). The latter value is based on • Residents are interested in learning more about each laser-videogrammetry-based length estimates for 1262 species; free-swimming individuals observed over five field sea- • Published reproductive information is lacking or incom- sons between depths of 0–94 m. plete; We calculated GSI values for 78 female Caesio cun- • Each species is distinctive enough that the chance of ing. The time period represented by our collection was misidentification is low. limited (21 February to 8 April, 2013), during this period Lengths, weights, and gonad samples are obtained GSI values appear elevated around the new moon in through regular village fishing activities, which include March (Fig. 3). hook-and-line, spear, and Derris fishing. These collecting We histologically examined gonads of 3 undifferenti- activities were approved by the relevant local and nation- ated, 49 male, and 80 female Caesio cuning. Figure 4 al authorities. shows examples of immature and mature testes and Our 2013 field season yielded a suitable number of specimens for analysis of the red-bellied fusilier, Caesio cuning (Bloch, 1791), and longfin emperor, Lethrinus ery- thropterus Valenciennes, 1830. Both are widespread food fishes in the Indo-Pacific. C. cuning ranges from Sri Lanka to Vanuatu and from southern Japan to northern Australia (Carpenter 1988). L. erythropterus ranges from the east coast of Africa to the Caroline Islands and from the Philippines to northwestern Australia (Carpenter 2001). With the following modifications, we used methods described in Longenecker et al. (2013a) to describe length–weight relations, size-at-maturity, reproductive mode, sex-ratios, and length-batch fecundity relations. For batch fecundity analysis, we analyzed ovarian sam- ples that had reached at least maturation (≥ stage IVa, see Longenecker et al. 2013b for a description of oocyte clas- sification) rather than late vitellogenesis (≥ IIIb), and we liberated oocytes from the stroma by vigorous shaking rather than with an ultrasonic cleaner. Additionally, we used a gonadosomatic index (GSI) to explore patterns of reproductive periodicity in females: GSI = 100GS–1 where: G is total gonad weight and S is somatic body weight. Results are summarized in Table 1 and presented more fully in separate sections for each species, below. Caesio cuning. Total body weight (W) in g is an approximate- ly cubic function of fork length (FL) in cm (Table 1, Fig. 2). 95% CI of regression parameters a and b are 0.0208 ± 0.1201 and 3.0322 ± 0.1139, respectively (r2 = 0.954, n = 137, Fig. 1. Map of the sampling area; Kamiali Wildlife FL range: 8.0–22.7, W range: 10–250). ANCOVA did not Management Area, Papua New Guinea, is bounded by detect a significant sex-based difference in the length–weight the Bitoi and Sela Rivers and includes Lababia and relation for this population (F = 3.56, DF = 1, P = 0.061). Jawani Islands; Scale bar = 1 km Reproduction and length–weight relation of C. cuning and L. erythropterus 77 ovaries. Ovaries of mature females contained several dis- those collected in March and April changed the L50 esti- crete stages of oocytes (Fig. 4B), indicating group-synchro- mate by a maximum 2 mm. nous oocyte development (Wallace and Selman 1981). We Our minimum-size-at-maturity (Lm) and L50 values for therefore classify C. cuning as a batch spawner. Sexual both sexes are substantially smaller than Lm estimates differentiation occurs around 12 cm FL. The smallest (26.7 cm for males, 32.3 cm for females) derived from the male with spermiated testes was 12.6 cm FL. For males, empirical equations of Froese and Binohlan (2000). For the size at which 50% of individuals are mature (L50) is instance, considering the more conservative of the size-at- 12.6 cm FL (Fig. 5). This estimate assumes one-half of maturity values we present, L50 for either sex is only 47% undifferentiated specimens were male. All males of the empirically derived Lm value. Because the estimate ≥ 18 cm were mature. Ovaries contained vitellogenic derived from Froese and Binohlan (2000) is based on oocytes in females as small as 15.1 cm FL.