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

Abstract

One of the most easily understood concepts in fishery management and conservation is to harvest individuals only after they have grown large enough to reproduce, thus allowing each generation to "seed" the next (Froese 2004). However the concept is difficult to put into practice because basic reproductive information such as size at maturity is lacking for~83% of exploited species worldwide (Froese and Binohlan 2000). This problem is especially intractable for coral-reef fishes; their sheer diversity, and the supposed cost associated with the reproductive analysis of each species are often cited as barriers to obtaining this important information (Roberts and Polunin 1993, Johannes 1998). Further, many Pacific island nations, where many of the world's coral reefs are located, have little or no capacity to conduct the reproductive research needed to support fishery management and conservation (Dalzell 1998). The reason for the latter problem may be as simple as a lack of basic infrastructure (e.g., electrical service needed to operate laboratory equipment) in many parts of these developing countries.To address these issues, and as part of a larger marineconservation effort (see Longenecker et al. 2013c), we initiated a research program to generate reproductive information for Pacific coral-reef fishes. We use recently developed methods for rapid, low-cost, on-site, histologybased reproductive analysis that requires minimal research infrastructure (Longenecker et al. 2013a(Longenecker et al. , 2013b. These methods use standard techniques (e.g., plastic embedding) that have been modified such that work can be conducted in remote field settings without electrical service. With these methods, reproductive information can be generated quickly and at low cost, thus eliminating 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 L 50 at 20.4 cm FL. Overall sex ratio of mature individuals is not significantly 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. RAPID REPRODUCTIVE ANALYSIS AND LENGTH-WEIGHT RELATION FOR RED-BELLIED FUSILIER, CAESIO CUNING, AND LONGFIN EMPEROR, LETHRINUS ERYTHROPTERUS (ACTINOPTERYGII: PERCIFORMES: CAESIONIDAE AND LETHRINIDAE) FROM

Rapid reproductive analysis and length–weight relations for five species of coral-reef fishes (Actinopterygii) from Papua New Guinea: Nemipterus isacanthus, Parupeneus barberinus, Kyphosus cinerascens, Ctenochaetus striatus (Perciformes), and Balistapus undulatus (Tetraodontiformes)

“…For instance, females of four of the five species in this study become less abundant as size class increases (Nemipterus isacanthus, Parupeneus barberinus, Ctenochaetus striatus, Balistapus undulatus). Similar patterns have been reported for confamilial species (Young and Martin 1985, Russell 1990, Lau and Sadovy 2001, Puentes Granada et al 2004, Mant et al 2006, Longenecker and Langston 2008, Langston et al 2009, Boaden and Kingsford 2013, Amira et al 2016, Pyle et al 2016) and members of other families (Longenecker et al 2014 subject to rapid reproductive analyses.…”

“…Although the pattern has been reported elsewhere, the impact of these size-specific sex ratios on which size classes are overwhelmingly responsible for populationlevel egg production is currently under-recognized (but see Longenecker et al 2014. It has long been a common assumption that large fish are disproportionately responsible for population-level reproductive output because large females produce many more eggs than small females (see Roberts and Polunin 1993, Allison et al 1998, Halpern 2003, Froese 2004, Birkeland and Dayton 2005, Sale et al 2005.…”

“…We disagree. Using the simplified methods we have described (Longenecker et al 2013a(Longenecker et al , 2013b(Longenecker et al , 2013c(Longenecker et al , 2014 histological analysis is fast and economical. Longenecker et al (2013a) estimated the cost of consumable supplies at $1.45 US per specimen.…”

“…However, in the interest of rapidly increasing the amount of available reproductive information, Jungle Histology uses only one gonad subsample from the minimum number of specimens necessary to generate estimates of reproductive parameters. Therefore, results should be viewed as preliminary (Longenecker et al 2014).…”

Many immature individuals and largest size classes lacked females for three coral reef fishes (Actinopterygii) in Fiji market surveys: Implications for fishery management

“…3B,5B,7C). This pattern has been reported elsewhere; however, its impact on the size classes overwhelmingly responsible for population-level egg production is under-recognized (but see Longenecker et al 2014Longenecker et al , 2017Longenecker et al , 2020. The common pattern of large females producing exponentially more eggs than small females has led to a longstanding assumption that large fish are disproportionately responsible for population-level egg production (Roberts and Polunin 1993;Allison et al 1998;Halpern 2003;Froese 2004;Sale et al 2005;Birkeland and Dayton 2005).…”