Improving estimates of growth for pearl perch (Glaucosoma scapulare) in Queensland, Australia

Abstract

The pearl perch (Glaucosoma scapulare) is endemic to the east coast of Australia in depths to 150 m. The species has a long history of exploitation, and the stock is currently depleted. Previous research indicated the species is long lived and slow growing based on fishery-dependent sampling undertaken in the late 1990s and early 2000s on traditional fishing grounds at the southern end of the species' range. Increasing fishing power has facilitated the expansion of the fishery to areas to the north and east of traditional grounds, which has resulted in the appearance of older fish (>10 yr) in fishery-dependent samples not previously observed. The current study estimated the growth parameters using 1153 length-at-age observations from fish collected in Queensland between January 2020 and December 2021. The lack of significant numbers of individuals at either end of the age frequency distribution necessitated the estimation of growth in a Bayesian framework with informative priors for lengthat-age-zero and maximum length using a multi-model approach. The von Bertalanffy growth function (VBGF) was found to best fit the observed length-at-age data and the estimated VBGF parameters were L ∞ = 562 mm FL, L 0 = 2.02 mm FL and k = 0.295 yr −1 .The high proportion of older fish in samples, combined with prior information on relevant parameters, improves growth parameter estimation by reducing bias and facilitating improved model fits to observed length-at-age data.

Sea Surface Temperature Affects the Reproductive Biology of Female Pearl Perch (Glaucosoma scapulare Macleay, 1881) in Queensland, Australia

“…Pearl perch are a member of the family Glaucosomatidae, which includes three other species: G. magnifcum (Ogilby, 1915), G. hebraicum (Richardson, 1845), and G. buergeri (Richardson, 1845). Pearl perch grow to 700 mm (total length, TL) and 7.3 kg [3] and have a maximum age of at least 27 years [4]. While this reported longevity is consistent with that of G. buergeri and G. hebraicum, 26 and 39 years, respectively [5,6], recent research indicates that pearl perch reach asymptotic size faster than either of these species [4].…”

“…Pearl perch grow to 700 mm (total length, TL) and 7.3 kg [3] and have a maximum age of at least 27 years [4]. While this reported longevity is consistent with that of G. buergeri and G. hebraicum, 26 and 39 years, respectively [5,6], recent research indicates that pearl perch reach asymptotic size faster than either of these species [4].…”

“…In the laboratory, all pearl perch were thawed, sexed, weighed (±0.01 g, for whole fsh only), and measured (fork length, FL, ±1 mm). After sagittal otolith pairs were removed to determine age and growth (see [4]), female ovary pairs were then removed, staged macroscopically (Table 1), and weighed (±0.0001 g). A section of some ovaries, classifed as developed (Stage 4) and spawning (Stage 5), was removed and fxed in 10% neutral bufered formalin for estimates of batch fecundity.…”

“…Maturity (0 � immature, 1 � mature) was the response variable, and FL (mm) or adjusted age (in years) were added as continuous explanatory variables. Ages assigned by Campbell et al [4] were adjusted for growth beyond the last complete opaque zone according to the marginal increment ratio (MIR): ages were increased by 0.33 year for otolith sections with 0 < MIR < 0.66 and 0.66 year for sections with MIR ≥ 0.66 [25]. All immature fsh were collected during fsheryindependent sampling conducted ofshore from Brisbane and the Sunshine Coast (Figure 1), and as such, maturity was assessed for fsh only caught in these areas to minimise any bias in the estimates of t 50 and L 50 resulting from the undersampling of immature animals in other areas.…”