Loss of plasticity in maturation timing after ten years of captive spawning in a delta smelt conservation hatchery

Adaptation to captivity in spawning programs can lead to unintentional consequences, such as domestication that results in reduced fitness in the wild. The timing of sexual maturation has been shown to be a trait under domestication selection in fish hatcheries, which affects a fish's access to mating opportunities and aligning their offspring's development with favorable environmental conditions. Earlier maturing fish may be favored in hatchery settings where managers provide artificially optimal growing conditions, but early maturation may reduce fitness in the wild if, for example, there is a mismatch between timing of reproduction and availability of resources that support recruitment. We investigated patterns of maturation timing in a delta smelt (Hypomesus transpacificus) conservation hatchery by quantifying changes to the median age at maturity since the captive spawning program was initiated in 2008. Over the span of a decade, we observed a small, but significant increase in age at maturity among broodstock by 2.2 weeks. This trait had low heritability and was largely controlled by phenotypic plasticity that was dependent on the time of year fish were born. Fish that were born later in the year matured faster, potentially a carryover from selection favoring synchronous spawning in the wild. However, higher DI (domestication index) fish showed a loss of plasticity, we argue, as a result of hatchery practices that breed individuals past peak periods of female ripeness. Our findings suggest that the hatchery setting has relaxed selection pressures for fish to mature quickly at the end of the year and, consequently, has led to a loss of plasticity in age at maturity. Hatchery fish that are re-introduced in the wild may not be able to align maturation with population peaks if their maturation rates are too slow with reduced plasticity, potentially resulting in lower fitness.

Captive-reared Delta Smelt (Hypomesus transpacificus) exhibit high survival in natural conditions using in situ enclosures

Conservation of endangered fishes commonly includes captive breeding, applied research, and management. Since 1996, a captive breeding program has existed for the federally threatened and California endangered Delta Smelt Hypomesus transpacificus, an osmerid fish endemic to the upper San Francisco Estuary. Although this program serves as a captive refuge population, with experimental releases being initiated to supplement the wild population, it was uncertain how individuals would survive, feed, and maintain condition outside hatchery conditions. We evaluated this and the effects of three enclosure designs (41% open, 63% open, and 63% open with partial outer mesh wrap) on growth, survival, and feeding efficacy of cultured Delta Smelt at two locations (Sacramento River near Rio Vista, CA and in Sacramento River Deepwater Ship Channel) in the wild. Enclosures exposed fish to semi-natural conditions (ambient environmental fluctuations and wild food resources) but prevented escape and predation. After four weeks, survival was high for all enclosure types (94-100%) at both locations. The change in condition and weight was variable between sites, increasing at the first location but decreasing at the second location. Gut content analysis showed that fish consumed wild zooplankton that came into the enclosures. Cumulatively, results show that captive-reared Delta Smelt can survive and forage successfully when housed in enclosures under semi-natural conditions in the wild. When comparing enclosure types, we observed no significant difference in fish weight changes (p = 0.58-0.81 across sites). The success of housing captive-reared Delta Smelt in enclosures in the wild provides preliminary evidence that these fish may be suitable to supplement the wild population in the San Francisco Estuary. Furthermore, these enclosures are a new tool to test the efficacy of habitat management actions or to acclimate fish to wild conditions as a soft release strategy for recently initiated supplementation efforts.

Experimental validation of otolith-based age and growth reconstructions across multiple life stages of a critically endangered estuarine fish

Background

The application of otolith-based tools to inform the management and conservation of fishes first requires taxon- and stage-specific validation. The Delta Smelt (Hypomesus transpacificus), a critically endangered estuarine fish that is endemic to the upper San Francisco Estuary (SFE), California, United States, serves as a key indicator species in the SFE; thus, understanding this species’ vital rates and population dynamics is valuable for assessing the overall health of the estuary. Otolith-based tools have been developed and applied across multiple life stages of Delta Smelt to reconstruct age structure, growth, phenology, and migration. However, key methodological assumptions have yet to be validated, thus limiting confidence in otolith-derived metrics that are important for informing major water management decisions in the SFE.

Methods

Using known-age cultured Delta Smelt and multiple independent otolith analysts, we examined otolith formation, otolith-somatic proportionality, aging accuracy and precision, left-right symmetry, and the effects of image magnification for larval, juvenile, and adult Delta Smelt.

Results

Overall, otolith size varied linearly with fish size (from 10–60 mm), explaining 99% of the variation in fish length, despite a unique slope for larvae < 10 mm. Otolith-somatic proportionality was similar among wild and cultured specimens. Aging precision among independent analysts was 98% and aging accuracy relative to known ages was 96%, with age estimates exhibiting negligible differences among left and right otoliths. Though error generally increased with age, percent error decreased from 0–30 days-post-hatch, with precision remaining relatively high (≥ 95%) thereafter. Increased magnification (400×) further improved aging accuracy for the oldest, slowest-growing individuals. Together, these results indicate that otolith-based techniques provide reliable age and growth reconstructions for larval, juvenile, and adult Delta Smelt. Such experimental assessments across multiple developmental stages are key steps toward assessing confidence in otolith-derived metrics that are often used to assess the dynamics of wild fish populations.

A pilot study of the performance of captive-reared delta smelt Hypomesus transpacificus in a semi-natural environment

A captive breeding programme was developed in 2008 for delta smelt Hypomesus transpacificus in reaction to dramatic population decline over several decades. We took 526 sub-adult captive-reared delta smelt and cultured them for 200 days without providing artificial food or water quality management to assess their performance once released in the wild. The results indicated captive-reared sub-adult delta smelt could survive in a semi-natural environment with uncontrolled water quality and naturally produced wild prey through spawning and into their post spawning phase.

A Conservation Hatchery Population of Delta Smelt Shows Evidence of Genetic Adaptation to Captivity After 9 Generations

Genetic adaptation to captivity is a concern for threatened and endangered species held in conservation hatcheries. Here, we present evidence of genetic adaptation to captivity in a conservation hatchery for the endangered delta smelt (Fish Conservation and Culture Laboratory, University of California Davis; FCCL). The FCCL population is genetically managed with parentage analysis and the addition of wild fish each year. Molecular monitoring indicates little loss of genetic variation and low differentiation between the wild and conservation populations. Yet, we found an increase in offspring survival to reproductive maturity during the subsequent spawning season (recovery rate) in crosses that included one or both cultured parents. Crosses with higher levels of hatchery ancestry tend to produce a greater number of offspring that are recovered the following year. The recovery rate of a cross decreases when offspring are raised in a tank with fish of high levels of hatchery ancestry. We suggest changes in fish rearing practices at the FCCL to reduce genetic adaptation to captivity, as delta smelt numbers in the wild continue to decline and the use of FCCL fish for reintroduction becomes more likely.

Conditional survival in Canada: adjusting patient prognosis over time

Five-year relative survival statistics are often used to measure cancer control across jurisdictions, and international comparisons such as the CONCORD or EUROCARE studies often point to substantial survival differences across participating countries [...]

Identification of a large cluster of coiled coil-nucleotide binding site--leucine rich repeat-type genes from the Rps1 region containing Phytophthora resistance genes in soybean

Fifteen Rps genes confer resistance against the oomycete pathogen Phytophthora sojae, which causes root and stem rot disease in soybean. We have isolated a disease resistance gene-like sequence from the genomic region containing Rps1-k. Four classes of cDNA of the sequence were isolated from etiolated hypocotyl tissues that express the Rps1-k-encoded Phytophthora resistance. Sequence analyses of a cDNA clone showed that the sequence is a member of the coiled coil-nucleotide binding site-leucine rich repeat (CC-NBS-LRR)-type of disease resistance genes. It showed 36% identity to the recently cloned soybean resistance gene Rpg1-b, which confers resistance against Pseudomonas syringae pv. glycinea, and 56% and 38% sequence identity to putative resistance gene sequences from lotus and Medicago truncatula, respectively. The soybean genome contains about 38 copies of the sequence. Most of these copies are clustered in approximately 600 kb of contiguous DNA of the Rps1-k region. We have identified a recombinant that carries both rps1-k- and Rps1-k-haplotype-specific allelomorphs of two Rps1-k-linked molecular markers. An unequal crossover event presumably led to duplication of alleles for these two physically linked molecular markers. We hypothesize that the unequal crossing over was one of the mechanisms involved in tandem duplication of CC-NBS-LRR sequences in the Rps1-k region.

Population genetic structure of rock ptarmigan Lagopus mutus in Northern and Western Europe

Alpine species may be losing habitat because of global warming. Setting management priorities for such species is thus urgent and cannot be achieved without data on population structure. We studied the structure of rock ptarmigan (Lagopus mutus) populations in the Pyrenees, Alps and Norway, using six microsatellites. We found that rock ptarmigan in the Pyrenees were genetically impoverished compared with those in the Alps and Norway, and displayed a greater divergence (Pyrenees vs. Alps or Norway: theta(ST) = 0.16, Alps vs. Norway, theta(ST) = 0.04). In the Alps, despite a weak genetic differentiation between localities up to 200 km apart (theta(ST) = 0.011), a significant isolation-by-distance (IBD) effect was detected. When computed for each sex separately this IBD effect was significant for males but not for females, suggesting that males are highly philopatric.

Trends in colorectal cancer incidence and mortality

OBJECTIVES

This article examines recent trends in the incidence of and mortality from colorectal cancer among Canadian men and women, then further analyzes trends by three subsites.

DATA SOURCES

Incidence data for colorectal cancer were obtained from the National Cancer Incidence Reporting System and from the Canadian Cancer Registry. Mortality data were extracted from the Canadian Vital Statistics Database. Supplementary data on nutrition are from the National Population Health Survey.

ANALYTICAL TECHNIQUES

Age-standardized incidence and mortality rates were calculated for men and women. Age-specific incidence and mortality rates were calculated by 10-year age groups. Joinpoint analysis was applied to detect statistically significant changes in linear trends.

MAIN RESULTS

Since the mid-1980s, colorectal cancer incidence has been declining, with steeper rates of decrease among women. Decreasing rates of colorectal cancer are limited to tumours located in the distal colon and rectum; the incidence of cancers of the proximal colon has not changed over time.

Early diagnosis of fetal bladder outlet obstruction

Prenatal ultrasonography has facilitated early diagnosis of in utero bladder outlet obstruction. This represents one of the earliest diagnoses of prune-belly syndrome and sheds light on the natural history of the bladder outlet obstruction in the fetus.

Safety and safety promotion: conceptual and operational aspects

After illustrating the main difficulties usually encountered in efforts to prevent injuries and improve the safety of populations, this paper will propose a frame of reference on the subject of safety promotion. It applies to the prevention of non-intentional injuries as well as to the problem of violent crimes and suicide. This framework should facilitate dialogue among those involved in these issues by encouraging better integration of the various prevention models used. It should also improve both the implementation and effectiveness of interdisciplinary and intersectorial interventions.

Acute mesenteric ischemia caused by isolated superior mesenteric artery dissection

Isolated dissection of a peripheral artery is a rare event. Only 11 reports exist in the literature of dissection of the superior mesenteric artery, most of which have been fatal. This is the first documented case of the successful treatment of an acute ischemic event caused by a superior mesenteric artery dissection. In addition, the new technique of right gastroepiploic artery-to-superior mesenteric artery bypass is introduced as a satisfactory method of revascularization.

Late pulmonary venous obstruction after surgical repair of infradiaphragmatic total anomalous pulmonary venous return

Twelve years after an apparently successful surgical correction of infradiaphragmatic (obstructed) total anomalous pulmonary venous drainage, a 12-year-old boy developed evidence of pulmonary artery hypertension secondary to pulmonary venous obstruction due to an apparent lack of growth at the anastomotic site.

Hypothermic circulatory arrest in the treatment of thoracic aortic lesions

The use of hypothermic circulatory arrest has been established in the treatment of aortic arch lesions. We recently used this method of arrest in the treatment of 10 consecutive patients with thoracic aortic lesions. Seven of these patients had dissecting aneurysms of the ascending aorta with extension into the aortic arch. One patient had a mycotic aneurysm of the arch, and 2 patients had arteriosclerotic aneurysms of the ascending aorta and entire aortic arch. All patients were supported and cooled with cardiopulmonary bypass. Circulatory arrest was maintained for periods of 21 to 63 minutes. All 10 patients survived the operative procedure. Nine patients remained intact neurologically. Renal function returned to baseline in all patients. Average blood replacement was 2.9 units. All patients have experienced an excellent surgical result. The average follow-up is 21.1 months. The technique facilitates a surgical approach to these lesions and appears to be the safest form of vital-organ preservation.