Red Throat Emperor Lethrinus Miniatus Research Articles

Sedentary or mobile? Variability in space and depth use of an exploited coral reef fish

Movement of fishes defines the distribution and abundance of populations and occurs on a range of spatial and temporal scales. To successfully parameterise assess- ments and design management strategies for exploited fish populations, knowledge and consideration of their move- ment patterns are essential. Since the efficacy of man- agement approaches vary depending on the sedentary or mobile nature of the target species, presence, space use and depth utilisation were examined to understand the move- ment patterns of redthroat emperor Lethrinus miniatus. Sixty individuals were monitored for up to 12 months in an acoustic array comprising three coral reefs, and variation in space use and movement patterns was observed among 26 individuals. Half of the individuals were recorded only in proximity of one receiver along the reef edge, while the other half were detected at multiple receivers and used horizontal areas of approximately 4 km 2 . Periods

Blood lactate loads of redthroat emperor Lethrinus miniatus associated with angling stress and exhaustive exercise

Baseline, post-angling and maximum attainable blood lactate concentrations were measured for the fishery species redthroat emperor Lethrinus miniatus to gain insight into the condition of fish released following c. 30 s angling and <45 s air exposure. Mean ± S.D. baseline blood lactate was 1·5 ± 0·6 mmol l⁻¹, which increased and plateaued around 6 mmol l⁻¹ at 15-30 min post-angling. These values were significantly lower than those obtained from fish maximally exhausted with a prolonged chase and air exposure protocol following capture (10·9 ± 1·8 mmol l⁻¹), suggesting that L. miniatus is not maximally exhausted during standard angling practices.

Informing the vulnerability of species to spawning aggregation fishing using commercial catch data

Fish spawning aggregations (FSAs) present a unique challenge for fishers and managers as aggregation fishing can be economically rewarding yet lead to overfishing and population collapse. Assessing the vulnerability of FSAs to fishing is often problematic due to a paucity of data. We present a tiered analysis for interrogating fishery logbook data for signals that fishing targets FSAs. We use two line fisheries that operate on Australia's Great Barrier Reef as models. The Reef Line Fishery (RLF) and Pelagic Line Fishery (PLF) operate across 9° of latitude, fishing occurs year round and the RLF has a seasonal spawning closure. A recent review reduced temporal closure days from 27 days to 10 days per year, though in the absence of any quantitative assessment of the vulnerability of targeted fish to increased harvest and hence risk. These fisheries target three reef fish groups (common coral trout Plectropomus leopardus, redthroat emperor Lethrinus miniatus, and a “other species” group mostly comprised of lethrinids and lutjanids) and a pelagic Scomberomorus commerson (narrow-barred Spanish mackerel). The tiered analyses captured the complete annual cycle of fish and fisher interaction across all latitudes and explored a number of catch metrics (landed catch, catch-per-unit-effort, and timing and size of large catch anomalies). No clear evidence of increased vulnerability of any of the three coral reef fish groups to fishing during spawning was found. Conversely the pelagic S. commerson is clearly more vulnerable to fishing during spawning. The tiered analytical approach is recommended as increased vulnerability of FSAs to fishing may not be identified by single analyses and without relative comparisons among species, the most vulnerable may be overlooked.

Large decline in the abundance of a targeted tropical lethrinid in areas open and closed to fishing

In Western Australia, one of the most important commercially and recreationally tar- geted, yet understudied fish species is the redthroat emperor Lethrinus miniatus. The present study aimed to compare the relative abundance and size of L. miniatus in areas open and closed to fishing at the Houtman Abrolhos Islands and to assess change in these populations over a 5 yr period. Baited remote underwater stereo-video systems (stereo BRUVs) were used to conduct the surveys from 2005 to 2009, which included different depths and locations across 4 geographically separated groups of islands. Data showed high spatial variability in the relative abundance of L. miniatus across depths, sites, and island group locations. In 2005 and 2006, L. miniatus were more abundant at depths of 22 to 26 m than in 8 to 12 m. At this time, individuals were also 1.3× more abundant and 10% larger in length in areas closed to fishing than in areas open to fishing. Starting in 2007, however, relative abundances of L. miniatus declined so markedly that in 2009 only 20% of the 2005 and 2006 numbers remained. This decline removed the disparity between depths, closed areas and fished locations. Unlike with relative abundance, L. miniatus remained consistently larger inside closed areas (mean 370 mm fork length) than in areas open to fishing (mean 350 mm). Of the 483 individuals measured across the 5 yr of the study, 98% were larger than the minimum legal size for retention, and therefore subject to harvest. Mean lengths increased each year, as the size structure of the population reflected an aging cohort. With declines in measured relative abundance in excess of 80% over the past 5 yr, the sustainability of L. miniatus assemblages at the Houtman Abrolhos Islands is in question.

Exploring movement patterns of an exploited coral reef fish when tagging data are limited

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 405:87-99 (2010) - DOI: https://doi.org/10.3354/meps08527 Exploring movement patterns of an exploited coral reef fish when tagging data are limited Ashley J. Williams1,2,*, L. Richard Little3, André E. Punt3,4, Bruce D. Mapstone3, Campbell R. Davies3, Michelle R. Heupel5 1Fishing and Fisheries Research Centre, School of Earth and Environment Studies, James Cook University, Townsville, 4811 Queensland, Australia 2Oceanic Fisheries Programme, Secretariat of the Pacific Community, BP D5, 98848 Noumea, New Caledonia 3CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, 7001 Tasmania, Australia 4School of Aquatic and Fishery Sciences, Box 355020, University of Washington, Seattle, Washington 98195-5020, USA 5School of Earth and Environmental Sciences, James Cook University, Townsville, 4811 Queensland, Australia *Email: ashleyw@spc.int ABSTRACT: Movement is one of the most fundamental demographic variables affecting the distribution and abundance of populations, but movement patterns for exploited populations of coral reef fish have not been studied extensively. Obtaining movement data for many species by means of traditional tagging methods can be difficult because of high tagging-induced mortality and low recapture rates. We used an age-structured population dynamics model parameterised using data from different regions to explore potential movement patterns for the red throat emperor Lethrinus miniatus, an exploited coral reef fish species for which traditional tagging studies have been unsuccessful. The model used a Gaussian function to describe the proportion of fish of a given age moving to or from 1 of 3 regions (Townsville, Mackay and Storm Cay) of the Great Barrier Reef. The model was fitted with and without movement to empirical age frequency data from each region over a 5 yr period (1995 to 1999). Including movement in the model led to significantly better fits to the data and revealed discrete movement patterns within each region. The model predicted net immigration to the Townsville region and net emigration from the Mackay and Storm Cay regions. We present alternative hypotheses about migration patterns of L. miniatus and highlight the importance of determining the scales at which movement in larger, exploited coral reef fishes occurs. KEY WORDS: Movement · Coral reef fish · Lethrinus miniatus · Great Barrier Reef · Modelling · Migration · Fisheries Full text in pdf format PreviousNextCite this article as: Williams AJ, Little LR, Punt AE, Mapstone BD, Davies CR, Heupel MR (2010) Exploring movement patterns of an exploited coral reef fish when tagging data are limited. Mar Ecol Prog Ser 405:87-99. https://doi.org/10.3354/meps08527 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 405. Online publication date: April 29, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Post mortem shrinkage of four species of temperate and tropical marine fishes, without freezing or preservation

The present study indicated significant post mortem decreases in length for four Australian teleost species from temperate to tropical habitats: black bream Acanthopagrus butcheri, King George whiting Sillaginodes punctata, summer whiting Sillago ciliata and redthroat emperor Lethrinus miniatus. Shrinkage averaged 5·0 mm after 24 h (range 0–10 mm) for A. butcheri, 4 mm (0–8 mm) for S. punctata, 2·2 mm (0·7–3·7 mm) for S. ciliata and 5·4 mm (−2·5–15·0 mm) for L. miniatus. For A. butcheri held under three different post mortem treatments, the mean length of fish in all treatments decreased but there was no significant effect of treatment type on the extent of shrinkage. The rate of shrinkage of S. ciliata varied with treatment, but the ultimate extent did not. For A. butcheri shrinkage was most rapid (2·5 mm h−1) between 1 and 2 h postcapture. The results from these studies confirm that a post mortem decrease in length is a common phenomenon, even in fishes that are not frozen or preserved. Such shrinkage has implications for the enforcement of minimum legal length legislation, and may cause bias in biological investigations, including growth estimates from tag and recapture studies.

Microsatellite variation and population genetic structure of the red throat emperor on the Great Barrier Reef

Analysis (using three analytical approaches) of eight microsatellite markers from six locations in three geographic regions of the Great Barrier Reef (GBR), including populations that differed in demographic characteristics, showed no evidence of genetic stock structure in the red throat emperor Lethrinus miniatus. Measures of inter‐population differentiation were non‐significant (P ≥ 0·67). Using a Bayesian clustering approach, ‘admixture’ was detected (mean alpha values &gt;1) with allele frequencies for each of the locations sampled being correlated equally with allele frequencies from all locations sampled. The number of populations (K) identified was one, based on the estimates of the probability of the data at various K values (K = 1, 2, 3, … 6). Additionally, alpha values did not stabilize to relatively constant values in any of the Bayesian analyses performed, indicating that there was no real genetic structure between locations. Analysis of genetic variation as detected by analysis of molecular variance (AMOVA) indicated that almost all of the variance in the data (99·74%, P ≤ 0·023) was within populations, rather than among populations (0·15%, P ≤ 0·176) or amongst regions sampled (0·10%, P ≤ 0·247) on the GBR. Fst statistics identified four individual loci having statistically significant differentiation among populations, but these were only related to one out of 12 pair‐wise comparisons where populations differed demographically. Given these results (albeit using neutral markers), together with the capacity of adults and larvae to be mobile between reefs on the inter‐connected GBR, it is considered unlikely that L. miniatus populations exist as distinct genetic stocks in the GBR. It is therefore not possible, using neutral markers, to reject the null hypothesis that the fishery be managed as a single panmictic stock.