Conservation successes and challenges for wide-ranging sharks and rays

Overfishing is the most significant threat facing sharks and rays. Given the growth in consumption of seafood, combined with the compounding effects of habitat loss, climate change, and pollution, there is a need to identify recovery paths, particularly in poorly managed and poorly monitored fisheries. Here, we document conservation through fisheries management success for 11 coastal sharks in US waters by comparing population trends through a Bayesian state-space model before and after the implementation of the 1993 Fisheries Management Plan for Sharks. We took advantage of the spatial and temporal gradients in fishing exposure and fisheries management in the Western Atlantic to analyze the effect on the Red List status of all 26 wide-ranging coastal sharks and rays. We show that extinction risk was greater where fishing pressure was higher, but this was offset by the strength of management engagement (indicated by strength of National and Regional Plan of Action for sharks and rays). The regional Red List Index (which tracks changes in extinction risk through time) declined in all regions until the 1980s but then improved in the North and Central Atlantic such that the average extinction risk is currently half that in the Southwest. Many sharks and rays are wide ranging, and successful fisheries management in one country can be undone by poorly regulated or unregulated fishing elsewhere. Our study underscores that well-enforced, science-based management of carefully monitored fisheries can achieve conservation success, even for slow-growing species

Overfishing Drives Over One-Third of All Sharks and Rays Toward a Global Extinction Crisis

The scale and drivers of marine biodiversity loss are being revealed by the International Union for Conservation of Nature (IUCN) Red List assessment process. We present the first global reassessment of 1,199 species in Class Chondrichthyes-sharks, rays, and chimeras. The first global assessment (in 2014) concluded that one-quarter (24%) of species were threatened. Now, 391 (32.6%) species are threatened with extinction. When this percentage of threat is applied to Data Deficient species, more than one-third (37.5%) of chondrichthyans are estimated to be threatened, with much of this change resulting from new information. Three species are Critically Endangered (Possibly Extinct), representing possibly the first global marine fish extinctions due to overfishing. Consequently, the chondrichthyan extinction rate is potentially 25 extinctions per million species years, comparable to that of terrestrial vertebrates. Overfishing is the universal threat affecting all 391 threatened species and is the sole threat for 67.3% of species and interacts with three other threats for the remaining third: loss and degradation of habitat (31.2% of threatened species), climate change (10.2%), and pollution (6.9%). Species are disproportionately threatened in tropical and subtropical coastal waters. Science-based limits on fishing, effective marine protected areas, and approaches that reduce or eliminate fishing mortality are urgently needed to minimize mortality of threatened species and ensure sustainable catch and trade of others. Immediate action is essential to prevent further extinctions and protect the potential for food security and ecosystem functions provided by this iconic lineage of predators

Development of an improved blood-stage malaria vaccine targeting the essential RH5-CyRPA-RIPR invasion complex

Reticulocyte-binding protein homologue 5 (RH5), a leading blood-stage Plasmodium falciparum malaria vaccine target, interacts with cysteine-rich protective antigen (CyRPA) and RH5-interacting protein (RIPR) to form an essential heterotrimeric “RCR-complex”. We investigate whether RCR-complex vaccination can improve upon RH5 alone. Using monoclonal antibodies (mAbs) we show that parasite growth-inhibitory epitopes on each antigen are surface-exposed on the RCR-complex and that mAb pairs targeting different antigens can function additively or synergistically. However, immunisation of female rats with the RCR-complex fails to outperform RH5 alone due to immuno-dominance of RIPR coupled with inferior potency of anti-RIPR polyclonal IgG. We identify that all growth-inhibitory antibody epitopes of RIPR cluster within the C-terminal EGF-like domains and that a fusion of these domains to CyRPA, called “R78C”, combined with RH5, improves the level of in vitro parasite growth inhibition compared to RH5 alone. These preclinical data justify the advancement of the RH5.1 + R78C/Matrix-M™ vaccine candidate to Phase 1 clinical trial

Preclinical development of a stabilized RH5 virus-like particle vaccine that induces improved antimalarial antibodies

Plasmodium falciparum reticulocyte-binding protein homolog 5 (RH5) is a leading blood-stage malaria vaccine antigen target, currently in a phase 2b clinical trial as a full-length soluble protein/adjuvant vaccine candidate called RH5.1/Matrix-M. We identify that disordered regions of the full-length RH5 molecule induce non-growth inhibitory antibodies in human vaccinees and that a re-engineered and stabilized immunogen (including just the alpha-helical core of RH5) induces a qualitatively superior growth inhibitory antibody response in rats vaccinated with this protein formulated in Matrix-M adjuvant. In parallel, bioconjugation of this immunogen, termed "RH5.2," to hepatitis B surface antigen virus-like particles (VLPs) using the "plug-and-display" SpyTag-SpyCatcher platform technology also enables superior quantitative antibody immunogenicity over soluble protein/adjuvant in vaccinated mice and rats. These studies identify a blood-stage malaria vaccine candidate that may improve upon the current leading soluble protein vaccine candidate RH5.1/Matrix-M. The RH5.2-VLP/Matrix-M vaccine candidate is now under evaluation in phase 1a/b clinical trials

Patterns in life history traits of deep-water chondrichthyans

Life history traits are important indicators of the productivity of species, and their ability to tolerate fishing pressure. Using a variety of life history traits (maximum size, size and age at maturity, longevity, growth rate, litter and birth size) we demonstrated life history differences between shelf, pelagic and deep-water habitats and within the deep habitat down the continental slope and across geographic regions. Deep-water species had lower growth rates, later age at maturity and higher longevity than both shelf and pelagic species. In the deep habitat, with increasing depth, species matured later, lived longer, had smaller litters and bred less frequently; regional differences in traits were also apparent. Deep-water species also had a smaller body size and the invariants of relative size and age at maturity were higher in deep-water. The visual interaction hypothesis offers a potential explanation for these findings and it is apparent habitat influences the trade-offs in allocation of energy for survival and reproduction. Body size is not appropriate as a predictor of vulnerability in deep-water chondrichthyans and regional trait differences are possibly due to a fishing pressure response. Deep-water chondrichthyans are more vulnerable to exploitation than shelf and pelagic species and this vulnerability markedly increases with increasing depth. The life history traits of deep-water chondrichthyans are unique and reflect adaptations driven by both mortality and resource limitations of their habitat

Comparison of life histories of two deep-water sharks from eastern Australia: the piked spurdog and the Philippine spurdog

Deep-water sharks have low biological productivity and are vulnerable to exploitation with species-specific regional life history required to enable effective management. The present study describes the life history of two squalids collected from Australia: (1) the piked spurdog (Squalus megalops) from the tropical Great Barrier Reef; and (2) the Philippine spurdog (S. montalbani) from New South Wales. Maximum observed ages for males and females were 18 and 25 years for S. megalops and 28 and 27 years for S. montalbani. Multiple growth models were all well supported and indicated very slow growth rates for both species. The tropical S. megalops population was smaller and older at maturity than previously reported temperate populations. Males were mature at 352-mm stretched total length (LST) and 12.6 years, whereas females were mature at 422 mm LST and 19.1 years. Squalus montalbani males were mature at 700 mm LST and 21.8 years, whereas females were mature at 800 mm LST and 26 years. Fecundity was lower for S. megalops than S. montalbani with two to three compared with nine to 16 embryos. Both species have a conservative life history, although in the event of overfishing the longer-lived, later-maturing and deeper-dwelling S. montalbani is likely to take longer to recover than S. megalops

Near-infrared spectroscopy for shark ageing and biology

Accurate and reliable age estimates of sharks are important for informing management that will achieve sustainable outcomes for populations. Age is the foundation of many of the essential parameters, such as growth rate and productivity, that are used in demographic analyses and fisheries assessments (Cailliet et al., 2006; Campana, 2001). Here, "sharks" is used as a general term to refer to sharks, rays, and chimaeras, therwise known as chondrichthyans. Traditionally, to estimate age in sharks, growth bands are counted in their hard parts. Vertebrae or dorsal fin spines are primarily used, although caudal thorns have also been found suitable for ageing in a few species of skates (Cailliet, 2015; Goldman et al., 2012; Serra-Pereira et al., 2008). As sharks age, calcified material accumulates in these structures and can produce visible band pairs that, when formation periodicity has been validated, enable age determination (Goldman et al., 2012; see also Chapter 10 in this volume). Counting these band pairs requires experience and time to achieve consistent results, and repeated reads are necessary to ensure precision of the counts (Cailliet et al., 2006). It also can require time-consuming preparation, such as sectioning of the structures and enhancement with stains to improve clarity and readability of the band pairs (Irvine et al., 2006b; Matta et al., 2017). In addition, this approach normally requires the lethal removal of the structures used for ageing from an individual. Given the vulnerability of many shark species to exploitation (Dulvy et al., 2014), nonlethal methods for ageing would be beneficial. These issues prompted investigation of near-infrared spectroscopy (NIRS) as a complementary approach to shark ageing. Although NIRS requires traditional band counts of some age structures, it can greatly reduce the time taken to estimate age from a structure and has the potential to be nonlethal (Rigby et al., 2014, 2016b). This chapter reviews how NIRS works and the application and considerations for use of NIRS in shark ageing

A novel use of near infrared spectroscopy: ageing deepwater sharks

To age sharks, the growth bands in the shark vertebrae (like the rings in a tree) or on the spines in front of each dorsal fin (which only some sharks have) are manually counted using a microscope. This is time-consuming and is only possible on dead animals. NIR spectroscopy is shown to be able to detect age in dorsal fin spines of sharks and hand-held NIR spectroscopy units could potentially be used for ageing of sharks in the field, at sea, using a hand-held unit to scan the fin spine on a live animal

The utility of near infrared spectroscopy for age estimation of deepwater sharks

Reliable age information is vital for effective fisheries management, yet age determinations are absent for many deepwater sharks as they cannot be aged using traditional methods of growth bands counts. An alternative approach to ageing using near infrared spectroscopy (NIRS) was investigated using dorsal fin spines, vertebrae and fin clips of three species of deepwater sharks. Ages were successfully estimated for the two dogfish, Squalus megalops and Squalus montalbani, and NIRS spectra were correlated with body size in the catshark, Asymbolus pallidus. Correlations between estimated-ages of the dogfish dorsal fin spines and their NIRS spectra were good, with S. megalops R^2=0.82 and S. montalbani R^2=0.73. NIRS spectra from S. megalops vertebrae and fin clips that have no visible growth bands were correlated with estimated-ages, with R^2=0.89 and 0.76, respectively. NIRS has the capacity to non-lethally estimate ages from fin spines and fin clips, and thus could significantly reduce the numbers of sharks that need to be lethally sampled for ageing studies. The detection of ageing materials by NIRS in poorly calcified deepwater shark vertebrae could potentially enable ageing of this group of sharks that are vulnerable to exploitation