The thin edge of the wedge: Extremely high extinction risk in wedgefishes and giant guitarfishes

1. The process of understanding the rapid global decline of sawfishes (Pristidae) has revealed great concern for their relatives, the wedgefishes (Rhinidae) and giant guitarfishes (Glaucostegidae), not least because all three families are targeted for their high‐value and internationally traded ‘white’ fins.
2. The objective of this study was to assess the extinction risk of all 10 wedgefishes and six giant guitarfishes by applying the International Union for Conservation of Nature (IUCN) Red List Categories and Criteria, and to summarize the latest understanding of their biogeography and habitat, life history, exploitation, use and trade, and population status. Three of the 10 wedgefish species had not been assessed previously for the IUCN Red List.
3. Wedgefishes and giant guitarfishes have overtaken sawfishes as the most imperilled marine fish families globally, with all but one of the 16 species facing an extremely high risk of extinction through a combination of traits: limited biological productivity; presence in shallow waters overlapping with some of the most intense and increasing coastal fisheries in the world; and overexploitation in target and by‐catch fisheries, driven by the need for animal protein and food security in coastal communities and the trade in meat and high‐value fins.
4. Two species with very restricted ranges, the clown wedgefish (Rhynchobatus cooki) of the Malay Archipelago and the false shark ray (Rhynchorhina mauritaniensis) of Mauritania, may be very close to extinction.
5. Only the eyebrow wedgefish (Rhynchobatus palpebratus) is not assessed as Critically Endangered, with it occurring primarily in Australia where fishing pressure is low and some management measures are in place. Australia represents a ‘lifeboat’ for the three wedgefish and one giant guitarfish species occurring there.
6. To conserve populations and permit recovery, a suite of measures will be required that will need to include species protection, spatial management, by‐catch mitigation, and harvest and international trade management, all of which will be dependent on effective enforcement.

     

Where have all the sawfishes gone? Perspectives on declines of these Critically Endangered species in Sri Lanka

1. All five species of sawfishes (family Pristidae) are amongst the most threatened marine fishes in the world, with steep population declines and local extinctions documented across their ranges.
2. Sawfishes have featured in Sri Lankan species checklists since 1889. However, landing records are extremely rare and little information is available on their status, diversity, and recent occurrences.
3. Interviews were conducted with 300 fishers and 10 fish traders. Only 39% of fishers (n = 118) could identify sawfishes, 37% had seen sawfishes (although half not since 1992), and only 10.7% had ever caught one. No respondents under 30 years could identify sawfishes. Older respondents (>50 years) were more likely to have caught sawfishes and reported seeing them frequently until 30 years ago, while younger respondents had only seen them at landing sites and, at most, once or twice in their life. Only 10 respondents had seen a sawfish in the last decade, suggesting that sawfishes were relatively abundant in the past but that populations have drastically declined.
4. Of the 32 respondents who had caught sawfishes, 30 reported declining numbers and attributed it to fishing pressure. These steep declines coincide with the time of increased fishing effort, the development of the aquaculture industry, and resulting degradation of coastal habitats in the 1980–1990s.
5. Overall, sawfishes had little cultural significance although fishers had specific names for the different species occurring here and rostra were sometimes donated to Catholic churches for ‘good luck’. Landed sawfishes were primarily sold for meat and traders appeared unaware of the high value of fins.
6. It is likely that sawfishes are now functionally extinct as a component of coastal ecosystems in Sri Lanka. Immediate action including species-specific legislation and critical habitat protection is urgently needed to provide remaining sawfishes and other sharks and rays with a fighting chance.

     

Differences in the composition and diversity of bacterial communities from agricultural and forest soils

Differences in the bacterial communities of soils caused by disturbances and land management were identified in rRNA gene libraries prepared from conventional tilled (CT) and no tilled (NT) cropland, a successional forest after 30 y of regrowth (NF) and an old forest of >65 y (OF) at Horseshoe Bend, in the southern Piedmont of Georgia (USA). Libraries were also prepared from forests after 80 y of regrowth at the Coweeta Long Term Ecological Research site (CWT) in the Southern Appalachians of western North Carolina (USA). The composition of the bacterial communities in cropland soils differed from those of the Horseshoe Bend OF and CWT forest soils, and many of the most abundant OTUs were different. Likewise, the diversity of bacterial communities from forest was less than that from cropland. The lower diversity in forest soils was attributed to the presence of a few, very abundant taxa in forest soils that were of reduced abundance or absent in cropland soils. After 30 y of regrowth, the composition of the bacterial soil community of the NF was similar to that of the OF, but the diversity was greater. These results suggested that the bacterial community of soil changes slowly within the time scale of these studies. In contrast, the composition and diversity of the bacterial communities in the Horseshoe Bend OF and Coweeta soils were very similar. Thus, this forest soil bacterial community was widely distributed in spite of the differences in soil properties, vegetation, and climate as well as resilient to disturbances of the above ground vegetation.     

EFFECT OF VENTILATION TECHNIQUE AND AIRWAY DIAMETER ON BRONCHIAL LUMEN TO PULMONARY ARTERY DIAMETER RATIOS IN CLINICALLY NORMAL BEAGLE DOGS

In dogs, a mean broncho‐arterial ratio of 1.45 ± 0.21 has been previously defined as normal. These values were obtained in dogs under general inhalational anesthesia using a single breath‐hold technique. The purpose of the study was to determine whether ventilation technique and bronchial diameter have an effect on broncho‐arterial ratios. Four healthy Beagle dogs were scanned twice, each time with positive‐pressure inspiration and end expiration. For each ventilation technique, broncho‐arterial ratios were grouped into those obtained from small or large bronchi using the median diameter of the bronchi as the cutoff value. Mean broncho‐arterial ratios obtained using positive‐pressure inspiration (1.24 ± 0.23) were statistically greater than those obtained at end expiration (1.11 ± 0.20) P = 0.005. There was a strong positive correlation between bronchial diameter and broncho‐arterial ratios for both ventilation techniques (positive‐pressure inspiration r_s = .786, P < 0.0005 and end expiration r_s = .709, P < 0.0005). Mean broncho‐arterial ratio for the large bronchi obtained applying positive‐pressure inspiration was 1.39 cm ± 0.20 and during end expiration was 1.22 cm ± 0.20. Mean broncho‐arterial ratio for the small bronchi obtained during positive‐pressure inspiration was 1.08 cm ± 0.13 and during end expiration was 1.01 cm ± 0.13. There was a statistically significant difference between these groups (F = 248.60, P = 0.005). Findings indicated that reference values obtained using positive‐pressure inspiration or from the larger bronchi may not be applicable to dogs scanned during end expiration or to the smaller bronchi.