The Great Barrier Reef (GBR) is a continental archipelagic system of 5000 reefs and shoals stretching >2000 km along the east Australia coast. The interconnectivity of these reefs should determine the choice of biological management units, which for most biota will reflect the dispersal of their eggs and/or larvae. A comparative approach using population genetics was used to ask whether the along—shore dispersal of coral reef fishes is influenced by the duration of this mobile phase. Seven species of coral reef fish, selected from three families to provide a range of taxonomic diversity and pelagic larval durations, were tested for genetic homogeneity between two regions of the GBR separated by 1000 km. A spectrum of potential dispersal capabilities was analyzed from that of Acanthochromis polyacanthus, a damselfish with brood care that uniquely lacks pelagic larvae, to that of Ctenochaetus striatus, a surgeonfish with large, specialized larvae that spend several months in the plankton. A total of 19 enzyme systems and general proteins were examined from multiple populations in each region to provide a base of 32 loci for these comparisons. With one exception, species sampled from different coral reefs within regions showed statistically significant heterogeneities across multiple loci, indicative of chaotic genetic patchiness among the samples. The exception was an anemonefish, Amphiprion melanopus, that had to be collected from large areas on each reef because of its low densities. The homogeneity of allele frequencies at local scales for this species suggests that the genetic patchiness observed in others may be a within—reef phenomenon that was manifested at the reef scale by our pseudoreplicated sampling strategy. After pooling local variability, all but two species showed significant regional differences. The exceptions were the pair (Ctenochaetus striatus, Pterocaesio chrysozona) with the longest larval durations. Acanthochromis polyacanthus showed increased variation at this larger scale, consistent with a major stock division between the two regions. The logarithm of genetic variation between northern and southern populations (measured by Weir and Cockerham's Fst was correlated with mean larval duration by an inverse linear relationship that explained 85% of the variance in the global data set. Comparison with an outgroup (Amphiprion melanopus from the Chesterfield Reefs, 1000 km east in the Coral Sea) confirmed the genetic cohesion of mainland populations for the species with shortest larval duration and shows that our empirical relationship applies only within the context of the highly connected GBR. On this basis, calculations of gene flow (Nem, the number of effective migrants per generation) between geographic regions predict panmixis for species with larval durations exceeding 1 mo. Many common species have shorter dispersal times, from which classical isolation—by—distance" models predict differentiation between northern and southern populations at genetic equilibrium. Given that modern populations...

A long-term, large-scale empirical test of the recruitment limitation hypothesis was done by sampling fish populations from the southern Great Barrier Reef after having monitored their recruitment histories for 9 years. After adjustment for demographic differences, recruitment patterns explained over 90 percent of the spatial variation in abundance of a common damselfish among seven coral reefs. The age structures from individual reefs also preserved major temporal variations in the recruitment signal over at least 10 years. Abundance and demography of this small fish at these spatial and temporal scales can be explained almost entirely as variable recruitment interacting with density-independent mortality.

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Objective: To investigate the effects of a 12 week comprehensive cardiac rehabilitation (CCR) programme on patients who have undergone implantation of an implantable cardioverter-defibrillator (ICD). Design: Sixteen patients with ICDs (14 (88%) male, mean (SD) age 58 (10) years, range 34-74 years) were randomised to either attend an individually tailored CCR programme or receive usual care. They then changed to the alternative regimen for a further 12 weeks. Exercise capacity was assessed using a treadmill exercise test at baseline, after usual care, after CCR and 12 weeks after CCR to assess maintenance effects. Hospital anxiety and depression (HAD) scores were recorded at each stage. Results: Exercise times (min:s; mean (SD)) increased by 16% from a baseline mean of 9:55 (2:33) to 11:11 (2:17) following attendance at CCR (95% confidence interval (CI) 0:34 to 1:58; p = 0.001). This improvement was maintained 12 weeks after attendance at CCR, at 11:20 (2:17) (p = 1.00). HAD scores for anxiety and depression decreased during CCR from a baseline of 13.4 (3.6) to 8.1 (3.6), 95% CI 3.5 to 7.0 (p < 0.001) and 9.9 (3.4) to 6.7 (2.9), 95% CI 1.9 to 4.4 (p = 0.002), respectively. These improvements were maintained at 12 weeks after CCR. No ventricular arrhythmias or ICD discharges occurred during the exercise components of the CCR. The total number of ventricular arrhythmias and ICD discharges was similar 12 weeks before, during, and 12 weeks after CCR.Conclusions: CCR appears to be safe for patients with ICDs. It can improve exercising ability and lower the levels of psychological distress. A larger multicentre study is recommended to confirm these findings.