Sharks are scarce in much of the Caribbean due to widespread depletion. Trinidad and Tobago, in the southern Caribbean, is a shark meat consumer and international exporter of dried shark fins. Despite limited fisheries management there is a small Marine Protected Area (MPA; 7 km2) in urbanised southwest Tobago, but its effect on sharks and rays (elasmobranchs) is unknown. The rural northeast is a recently designated UNESCO Man and the Biosphere Reserve with a significant marine component and plans for a large MPA, but no baseline data for elasmobranchs exist. Given the local importance of elasmobranchs and a newly drafted Sustainable Shark and Ray Management Plan, we used baited remote underwater video stations within a 40 m depth contour at 270 randomly generated points around Tobago to: (i) establish a baseline of species richness and relative abundance, (ii) investigate the influence of season, habitat relief, depth and water temperature on relative abundance, and (iii) investigate spatial variation in relative abundance. Caribbean reef sharks, nurse sharks, and southern stingrays were observed at all sites, the latter two more frequently in the urbanised southwest. Shark diversity was unexpectedly high in the northeast, driven by rarer species (sharpnose, smoothhound, tiger, scalloped hammerhead, great hammerhead) only observed there. Habitat relief, depth and season likely influence relative abundance of elasmobranchs around Tobago, but research is needed to elucidate species-level effects. Shark species richness in northeast Tobago is high for the Caribbean, warranting research attention, while the larger MPA presents an opportunity to strengthen elasmobranch management.

The objective of this paper was to characterize bycatch in an experimental fishery for Patagonian toothfish in Ecuador during 2017–2021. Diversity was analysed using Shannon, Margalef, Simpson, and Dominance indices. Bycatch representativity was calculated as the difference percentage between the target catch and non-target, in weight. The bycatch comprised 51 taxa and was composed primarily of fish. In addition, 12 species of pelagic habits (i.e. fishes and sharks) were also captured during the deployment/retrieval of fishing gear. The most frequent species (by number of individuals) were chimaeras (Hydrolagus melanophasma), grenadiers (Antimora rostrata, Coryphaenoides delsolari, and Coryphaenoides armatus), and sharks (Etmopterus granulosus and Centroscymnus owstonii). The diversity was medium low, according to the Shannon indices (0.5–1.8), with a negative trend for dominance and a positive trend for equitability.

Theorems of hyperarithmetic analysis (THAs) occupy an unusual neighborhood in the realms of reverse mathematics and recursion theoretic complexity. They lie above all the fixed (recursive) iterations of the Turing Jump but below ATR $_{0}$ (and so $\Pi _{1}^{1}$ -CA $_{0}$ or the hyperjump). There is a long history of proof theoretic principles which are THAs. Until Barnes, Goh, and Shore [ta] revealed an array of theorems in graph theory living in this neighborhood, there was only one mathematical denizen. In this paper we introduce a new neighborhood of theorems which are almost theorems of hyperarithmetic analysis (ATHAs). When combined with ACA $_{0}$ they are THAs but on their own they are very weak. We generalize several conservativity classes ( $\Pi _{1}^{1}$ , r- $\Pi _{2}^{1}$ , and Tanaka) and show that all our examples (and many others) are conservative over RCA $_{0}$ in all these senses and weak in other recursion theoretic ways as well. We provide denizens, both mathematical and logical. These results answer a question raised by Hirschfeldt and reported in Montalbán [2011] by providing a long list of pairs of principles one of which is very weak over RCA $_{0}$ but over ACA $_{0}$ is equivalent to the other which may be strong (THA) or very strong going up a standard hierarchy and at the end being stronger than full second order arithmetic.

A number of Tursiops truncatus mandibles in the collection of fossil marine mammals in the Rotterdam Natural History Museum have marks consisting of several parallel linear grooves. These marks are also found on four atlas complexes, a scapula and on one vertebra. The hypothesis that they are bite marks and were caused by scavenging rays (Rajidae, Chondrichthyes) was tested with a real-life experiment using different shark and ray species, allowing them to scavenge on cow ribs as proxies for the dolphin bones. The bite marks of these animals were compared with the fossil marks and show that the fossil marks are most likely caused by scavenging rays.

Hooking (or “at-haulback”) fishing mortality was analysed in elasmobranchs captured byPortuguese longliners targeting swordfish in the Atlantic Ocean. Information was collectedby on-board fishery observers who monitored 834 longline fishing sets between August 2008and December 2011, and recorded information on 36 067 elasmobranch specimens from 21different taxa. The hooking mortality proportions were species-specific, with some specieshaving relatively high percentages of live specimens at time of haulback (e.g., blueshark, crocodile shark, pelagic stingray, manta, devil and eagle rays), while others hadhigher percentages of dead specimens (e.g., smooth hammerhead, silky shark, bigeyethresher). For the most captured species (Prionace glauca, Pseudocarchariaskamoharai, Isurus oxyrinchus and Alopias superciliosus),logistic generalized linear models (GLMs) were carried out to compare the mortality ratesbetween sexes, specimen sizes and the regions of operation of the fleet. The sex-specificproportions of hooking mortality were significantly different for blue and crocodilesharks, with the males of both species having higher proportions of hooking mortality thanthe females. Specimen size was significant for predicting the hooking mortality for blueand shortfin mako sharks: in both cases, the larger specimens had lower odds of dying dueto the fishing process. There were differences in the hooking mortality depending on theregion of operation of the fleet, but those differences were also species-specific. Forblue and crocodile sharks, the hooking mortality was higher in the Equatorial and southernAtlantic areas (when compared to the NE Atlantic region), while the opposite was observedfor the shortfin mako, with lower mortality rates in the NE tropical area compared withthe other regions. The results presented in this paper can be integrated into futureecological risk assessment analysis for pelagic elasmobranchs. Furthermore, the newinformation can be used to evaluate the impact of recent recommendations prohibiting theretention of some vulnerable elasmobranch species.

An individual of the cowtail stingray (Pastinachus sephen) was identified at Ningaloo Reef, Western Australia as having a high number of parasitic leeches and gnathiid isopods primarily inhabiting its mouth, jaw and gills. It was underweight for its length and disc width when compared with other individuals of this species and its stomach was bloated and empty. It is proposed that the high density of these parasites directly led to the physical degradation and bodyweight of this individual. In addition to observing two previously undescribed hosts from this location, this is also a new locality record for this species of parasitic leech in Western Australia.

The present study provides a check list of elasmobranchs from the Paraná State coast, southern Brazil. Information from fish collections, literature data, field surveys and personal communications were included. Results indicated that 83 species from seven orders and 28 families were recorded. According to the results 51 species belonging to six orders and 17 families of sharks; and 32 species belonging to one order and eleven families of rays occur in this region. The most species-rich families were Carcharhinidae (14 species) and Arhynchobatidae (eight species).

Consider a compact body E embedded in a convex compact body G. A point P is randomly chosen in E and three different rays to the boundary ∂G of G are generated by P. Ray is in a uniformly random direction and has length R, ray is through a second random point chosen from within G and has length W, and ray is to a random point in ∂G and has length Y. The distribution of Y is obtained and is related to previous work. When E is specialized to G or to ∂G, other known results are retrieved. The paper ends with a discussion of a conjecture relating the means of R, W and Y.