Abundance and exploitation rate of the blue crab (Callinectes sapidus) in Chesapeake Bay

We estimated absolute abundance of the blue crab stock in Chesapeake Bay during winter from stratified random surveys conducted baywide from 1990 to 1999, using the swept-area method. We estimated catching efficiency of the survey gear from multiple depletion experiments to correct for temporal and vessel/area differences in catchability. The survey was conducted during the winter, when crabs are dormant and buried in the bottom. Analysis of crab carapace width (CW) frequency distributions revealed two size modes: CW less or equal 60 mm and CW greater than 60 mm, corresponding to age-0 (recruits) and age-1+ (one year and older), respectively. Absolute density of blue crab recruits varied from 10 to 55 crabs per 1,000 m(2) across years (95 million to 540 million baywide), with no significant trends over time. Abundance of age-1 + crabs declined significantly from 35 to 38 crabs per I 000 m(2) in 1990-1991 (342 million to 371 million crabs baywide) to 8.3 in 1999 (92 million crabs baywide). A stronger decline in the number of males indicates that males were exploited more intensively than females. A three-year moving average of spawning stock abundance (age- 1+ females) declined twofold from the early to the late 1990s. The absolute abundance of the blue crab population in Chesapeake Bay varied from 241 million to 867 million. Over-wintering mortality was usually less than 2%, but substantially higher mortality occurred in 1994 (7.3%) and 1996 (11.9%). High correlation between January water temperature and the percentage of dead crabs provides strong evidence of the adverse effect of cold winter on survival of crabs. Large crabs were affected most by cold winter temperatures. We estimated exploitation rates for the commercial fishery by comparing abundance with total landings. The estimated exploitation rates varied from 40% to 52% from 1990 to 1998 and increased to a record high of 70% in 1999. Fishing mortality rates varied from 0.6 to 0.9 year(-1) ill most years and were above the level providing maximum yield per recruit (F-max = 0.64 year(-1)) in nearly all years. The record fishing mortality in 1999 (F-1999, = 1.6 year(-1)) exceeded the overfishing threshold (F-10% = 1.0 year(-1)). Despite evidence of growth overfishing, the blue crab population supported large harvests throughout the 1990s. Increase of fishing mortality above the F-10% in 1999, indicates that the population was overfished and is at risk of recruitment overfishing if fishing mortality remains at this level

Genetics and evidence for balancing selection of a sex-linked colour polymorphism in a songbird

Colour polymorphisms play a key role in sexual selection and speciation, yet the mechanisms that generate and maintain them are not fully understood. Here, we use genomic and transcriptomic tools to identify the precise genetic architecture and evolutionary history of a sex-linked colour polymorphism in the Gouldian finch Erythrura gouldiae that is also accompanied by remarkable differences in behaviour and physiology. We find that differences in colour are associated with an ~72-kbp region of the Z chromosome in a putative regulatory region for follistatin, an antagonist of the TGF-β superfamily genes. The region is highly differentiated between morphs, unlike the rest of the genome, yet we find no evidence that an inversion is involved in maintaining the distinct haplotypes. Coalescent simulations confirm that there is elevated nucleotide diversity and an excess of intermediate frequency alleles at this locus. We conclude that this pleiotropic colour polymorphism is most probably maintained by balancing selection

International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine

Abstract Creatine is one of the most popular nutritional ergogenic aids for athletes. Studies have consistently shown that creatine supplementation increases intramuscular creatine concentrations which may help explain the observed improvements in high intensity exercise performance leading to greater training adaptations. In addition to athletic and exercise improvement, research has shown that creatine supplementation may enhance post-exercise recovery, injury prevention, thermoregulation, rehabilitation, and concussion and/or spinal cord neuroprotection. Additionally, a number of clinical applications of creatine supplementation have been studied involving neurodegenerative diseases (e.g., muscular dystrophy, Parkinson’s, Huntington’s disease), diabetes, osteoarthritis, fibromyalgia, aging, brain and heart ischemia, adolescent depression, and pregnancy. These studies provide a large body of evidence that creatine can not only improve exercise performance, but can play a role in preventing and/or reducing the severity of injury, enhancing rehabilitation from injuries, and helping athletes tolerate heavy training loads. Additionally, researchers have identified a number of potentially beneficial clinical uses of creatine supplementation. These studies show that short and long-term supplementation (up to 30 g/day for 5 years) is safe and well-tolerated in healthy individuals and in a number of patient populations ranging from infants to the elderly. Moreover, significant health benefits may be provided by ensuring habitual low dietary creatine ingestion (e.g., 3 g/day) throughout the lifespan. The purpose of this review is to provide an update to the current literature regarding the role and safety of creatine supplementation in exercise, sport, and medicine and to update the position stand of International Society of Sports Nutrition (ISSN)