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Volume 25, Issue 4 – 15 October 2019

Volume 25, Issue 4 – 15 October 2019
New Scientific publication – started delivery on October 15, 2019

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Ivan Sazima: Eating out: the Australian pufferfish Tetractenos hamiltoni lunges or blows water at prey situated above water level, pp. 125-132

Among the about 30,000 recognized fish species, a handful of them lunges/jumps or spits water at terrestrial prey. The Common Toadfish Tetractenos hamiltoni is a frequent pufferfish in Australian estuaries and mangroves, and feeds opportunistically on anything assessed as edible. I report on two noteworthy foraging behaviours of this pufferfish at a rocky embankment in an estuarine habitat in urban Sydney, south-eastern Australia. Pufferfish usually foraged over the submerged rocks catching crabs and snails, and at water surface they visually examined and/or mouthed and ate floating objects such as insects alive or dead and berries. Some individuals employed a particular foraging mode: they swam very close to rocks that were partly above water level, and inspected every object that resembled a potential prey. The intertidal isopod Ligia australiensis was the prey most sought after. From time to time, the fish stopped in front of these potential preys and appeared to evaluate their availability for a preying attempt. Afterwards, the pufferfish either lunged/jumped out of the water to grab the prey, or exposed the head above the surface and forcefully expelled water from the mouth (spat) at the prey. Hunting success was about 15% for lunging and 10% for spitting. These observations raise to two the pufferfish species recorded to lunge/jump out of the water to secure a prey above water level, and add the Common Toadfish to the fish species that spit at a potential food item.

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The Common Toadfish Tetractenos hamiltoni examines potential preys while foraging at an estuarine rocky embankment. a) An individual visually inspects an Australian marine slater (Ligia ustraliensis) on a rock above water level asterisk). b) Another individual inspects a rock with its left eye, while the right one scans the surroundings. Photos by I. Sazima

Ivan Sazima: Hiding in plain sight: a summary of defensive tactics of fishes in mangroves and tidal creeks of northern coast of São Paulo, Brazil, pp. 133-148

Mangroves and tidal creeks harbour rich and varied fish assemblages composed mostly of small, juvenile, and larval individuals. Fish species that forage on the bottom or in the water column in open areas would be at greater risk of predation by visually-oriented hunters (piscivorous birds and fishes) than fish species that forage among vegetation. I studied open areas of shallow and clear stretches of two mangroves, two tidal creeks, and one inlet under freshwater influence in southeastern Brazil, and recorded morphological features and behavioural tactics that would lessen predation risks imposed to the fishes by piscivorous birds and fishes. Besides antipredator tactics of the fishes, I recorded potential visually-hunting predators at the same sites. Among the 24 fish species recorded, camouflage was the most common tactic and included crypsis (background matching and countershading) and masquerade (resemblance to decaying plant pieces). Transparency or translucency was another common form of camouflage, although restricted to larval stages. I also recorded instances of warning colouration, Batesian mimicry, and social mimicry. Fish species that used camouflage or mimicry as defensive tactics displayed particular behaviours, as well as colour changes, which enhanced their disguise. Most summaries and reviews on protective resemblance focus on fish species rather than habitats, and observational studies on defensive tactics against visually-guided predators in diverse habitats would be very instructive.

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Crypsis by background matching as a defensive tactic in two bottom-associated species in a tidal creek. a) Bay Whiff Citharichthys spilopterus juvenile (about 90 mm TL). b) American Freshwater Goby adult Ctenogobius shufeldti (about 20 mm TL). Photos by I. Sazima.

Stefano Valdesalici and José Ramón García Gil: A new killifish from central Bolivia: Anablepsoides bibosi (Cyprinodontiformes: Rivulidae), pp. 149-154

Anablepsoides bibosi, new species, is here described from a stream in central Bolivia, in the Rio Chapare drainage, a tributary of Rio Mamoré, Amazon basin. The new species is a member of the A. limoncochae species group and differs from all the other species of this assemblage by its unique colour pattern and some morphological differences.

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Anablepsoides bibosi, MSNG 61243, male, holotype, 37.2 mm SL, Bolivia, Departamento Cochabamba, Rio Chapare drainage. Photo by J. R. García Gil.

Jeremy Kenneth Dickens: Annotated checklist to the fish of Laguna Blanca, San Pedro, Paraguay, pp. 155-178

Despite the high fish diversity of the Paraguay basin, there is still large uncertainty about the presence and distribution of species in the country of Paraguay. Here, I present an annotated checklist to the fish of Paraguay’s only true lake, Laguna Blanca, in San Pedro department, based on samples collected opportunistically between 2012 and 2017. A total of 32 species from 16 families and 6 orders were found, although the actual total is estimated at between 36 and 58 species. This included an unnamed species of Hemigrammus and the first country record of Moenkhausia bonita. Live colouration is also described for Hemigrammus mahnerti. One species was endemic to Paraguay, four to the Paraguay river basin, eight to the Paraná-Paraguay and 15 to the Rio De La Plata, whilst two were potamodromous. Species composition is typical of Neotropical lentic systems but with a distinct scarcity of benthivores, likely associated with the oligotrophic conditions of the lake. The threats to this unique ecosystem, through uncontrolled development, illegal deforestation, pollution and overfishing are imminent and recommendations for its protection are given.

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a) Interpolated (solid line) and extrapolated (broken line) species rarefaction curves with 95 % confidence intervals and b) actual species accumulation curve of fish collected at Laguna Blanca.

John E. Randall, Kimberly R. Andrews and Iria Fernandez-Silva: The Indo-Pacific Red Snapper Etelis carbunculus Cuvier (in Cuvier & Valenciennes 1828) proposed as a swarm, pp. 179-184

Data and photographs are provided to demonstrate that the Indo-Pacific Red Snapper Etelis carbunculus Cuvier (in Cuvier & Valenciennes) is a swarm, defined as a population of individuals of a species that are able to reproduce, despite being so different in color and some features of morphology that any two might appear to be different species.

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Etelis carbunculus, BPBM 19207, 273 mm SL, Okinawa fish market. Photo by J. E. Randall.

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