Sympatric elasmobranchs and fecal samples provide insight into the trophic ecology of the smalltooth sawfish

Poulakis, Gregg R.; Urakawa, Hidetoshi; Stevens, Philip W.; DeAngelo, Jacquelyn A.; Timmers, Amy A.; Grubbs, R. Dean; Fisk, Aaron T.; Olin, Jill A.

doi:10.3354/esr00824

Cited by 23 publications

(29 citation statements)

References 78 publications

(83 reference statements)

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“…They are distributed across coastal areas, estuaries, and freshwaters from tropical to subtropical regions -especially in shallow, sandy, or muddy bottoms. The saw is used mainly for feeding purposes, such as to scour the bottom for benthic prey or to capture free-swimming ray-finned fishes (Wueringer et al 2012, Poulakis et al 2017. However, rostral ex pansion is also the main cause of entanglement in fishing nets (Dulvy et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Sawfish (Pristidae) records along the Eastern Amazon coast

Feitosa¹,

Martins²,

Nunes³

2017

Endang. Species. Res.

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Sawfishes are the most endangered cartilaginous fishes on the planet. Their external morphology facilitates entanglement in fishing nets and their K-selected life history hinders the recovery of exploited populations. The Eastern Amazon coast (EAC) is known to be an area where sawfishes occur in Brazil, but few studies have been conducted in the area to better understand their biology and ecology. The present study reports sawfish captures along the coast of Brazil's second largest state. Data were collected from interviews with fishermen, a literature review, and media reports. In total, 23 captures were recorded between 1984 and 2016. Records include adults, a pregnant female with near-term embryos, juveniles, and young-of-the-year specimens. Most catches were reported in the Canal do Navio, an area under strong human pressure. Sawfish saws are valuable items and, for many anglers in precarious economic and social situations, high market prices eclipse the fishing prohibitions laid down under federal laws. Urgent research is required to understand sawfishes' life history, identify their critical habitats, and effectively manage and conserve these species along the EAC.

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Section: Introductionmentioning

confidence: 99%

Sawfish (Pristidae) records along the Eastern Amazon coast

Feitosa¹,

Martins²,

Nunes³

2017

Endang. Species. Res.

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“…Notably, they identified striped mullet Mugil cephalus, Clupeiformes, and Carangidae as part of the diet. Our data suggest that fisher's knowledge of sawfish diet is reasonably good; the lack of snook and tarpon in the fecal samples could be explained by the small sample size of Poulakis et al (2017) or the low importance of these species in their study area. Several fishers related how they used to see sawfishes slash through schools of fishes in estuaries or river mouths to feed, hitting some fishes during the slashing and then turning back to pick them up once dead or injured.…”

Section: Biology and Ecologymentioning

confidence: 75%

“…This highlights the importance of continuing to collect fishers' knowledge to learn about these species. Poulakis et al (2017) analyzed stable isotopes from fin clips of > 200 smalltooth sawfish and also fecal samples from 4 individuals from Florida and reported a diet based on teleosts and batoids. Notably, they identified striped mullet Mugil cephalus, Clupeiformes, and Carangidae as part of the diet.…”

Section: Biology and Ecologymentioning

confidence: 99%

Tapping into local ecological knowledge to assess the former importance and current status of sawfishes in Mexico

Bonfil¹,

Ricaño-Soriano²,

Mendoza-Vargas³

et al. 2018

Endang. Species. Res.

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Information on the occurrence and abundance of the Critically Endangered smalltooth sawfish Pristis pectinata and largetooth sawfish P. pristis across most of their former range is needed for a comprehensive global conservation status assessment. The current presence of both species in Mexico and the rest of Latin America remains uncertain in the absence of dedicated studies. During 2015, we performed the first nationwide study of sawfishes in Mexico. We developed specific materials to survey fishers, raise community awareness, and publicize sawfish conservation needs. We interviewed 794 fishers in 71 localities along the Atlantic and Pacific coasts of Mexico. Additional data from a similar 2010−2011 survey of 39 fishers in Tabasco and Campeche were also included in the analysis. Both species might be nearly extirpated from Mexico. Interviewees reported modal decadal dates of last sighting as the 1980s for the smalltooth sawfish along the Atlantic coast and as the 1970s for the largetooth sawfish along both coasts. No confirmed reports of recent (< 5 yr) sightings were reported. However, a live juvenile smalltooth sawfish was caught in Veracruz in January 2016. Historical importance maps were reconstructed, indicating that both species were distributed along the entire surveyed area; the smalltooth sawfish was especially common in Campeche, Quintana Roo, and Tabasco, while the largetooth sawfish was common in Campeche, Colima, and Chiapas. Both species must be re-categorized in Mexican legislation for species at risk of extinction from 'threatened' to 'endangered'.

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“…8,[32][33][34] ), a distilled water rinse followed by a chloroform/methanol 2:1 rinse (e.g. 35 ), or cyclohexane rinses (e.g. 36 ).…”

Section: Discussionmentioning

confidence: 99%

Effects of pre‐treatments on bulk stable isotope ratios in fish samples: A cautionary note for studies comparisons

Connan

Hall

Smale

2019

Rapid Comm Mass Spectrometry

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Rationale Stable isotope analysis (SIA) has revolutionised ecological studies over the past thirty years. One of the major fields where SIA is applied in the marine environment is related to the definition of ecosystem structure and function. With marine top predators such as sharks, SIA is a method of choice because tissue samples can be collected without the sacrifice of the animal. In elasmobranch research, the influence of compounds such as urea, trimethylamine oxide and lipids must be considered when using stable isotopes as ecological markers. Currently, a range of pre‐treatments are used to chemically remove these molecules prior to SIA. Methods This study investigated the impact of eleven commonly used pre‐treatments on carbon and nitrogen contents and C:N atomic ratio, as well as carbon and nitrogen SI ratios in elasmobranch tissues and its prey, measured by isotope ratio mass spectrometry. Three tissues were tested: blood and muscle of the ragged‐tooth shark Carcharias taurus, and muscle of one teleost species, the Cape knifejaw Oplegnathus conwayi. Results Compared with untreated samples, no trend or generalisation could be highlighted with the influence of pre‐treatments being species‐, tissue‐ and chemical‐element‐dependent. For the δ13C and δ15N values, differences among pre‐treatments were as high as 3‰, therefore potentially leading to erroneous ecological interpretation. Conclusions The chemical properties of compounds (e.g. urea, lipids) combined with the polarity of solutions (e.g. water, solvents) explained a large part of these observations. This study highlights that pre‐treatments need to be considered especially when comparing carbon and nitrogen stable isotope ratios between studies. The results of this study provide a call to all stable isotope researchers to make a concerted effort to standardise pre‐treatment methods. This is crucial as global reviews are becoming increasingly more informative.

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Sympatric elasmobranchs and fecal samples provide insight into the trophic ecology of the smalltooth sawfish

Cited by 23 publications

References 78 publications

Sawfish (Pristidae) records along the Eastern Amazon coast

Sawfish (Pristidae) records along the Eastern Amazon coast

Tapping into local ecological knowledge to assess the former importance and current status of sawfishes in Mexico

Effects of pre‐treatments on bulk stable isotope ratios in fish samples: A cautionary note for studies comparisons

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