Invasive crayfish can cause high fisheries damage

In Zambia and Zimbabwe, a single crayfish may cause annual fishery losses of as much as $6.15

Guest blog post by Josie South

Invasive crayfish have the potential to cause high economic cost to artisanal fisheries in southern Africa through scavenging behaviour and destroying fish fry habitat.

A recent study by C∙I∙B Research Associate Josie South (University of Leeds, UK) with scientists from the South African Institute for Aquatic Biodiversity (SAIAB) quantified the damage caused by two invasive crayfish compared to native crab species, at two temperatures, on tilapia catch and macrophytes.

Redclaw crayfish entangled in a gill net in the Kafue River. Photo by Bruce Ellender

Economic costs of invasive species are vital to prioritise and incentivise management spending to reduce and restrict invasive species. No economic costs have been published for the global invader – the redclaw crayfish (Cherax quadricarinatus), and none for the entire continent of Africa. Another prolifically invasive crayfish, the red swamp crayfish (Procambarus clarkii) is also invasive in various countries of southern Africa. Anecdotal reports of crayfish scavenging from artisanal gillnet fisheries are abundant across the invasive ranges but lacked quantification. Similarly anecdotal information about macrophyte stands being destroyed by crayfish has been reported.

For their study, Josie and colleagues compared the feeding rates per gram of crayfish to that of the native Potamonautid crabs at 19°C and 28°C on simulated fisheries catch and macrophytes to identify how much damage may be caused.

Gill net fish catch damaged by crayfish scavenging. Photo by Josie South

The red swamp crayfish consumed the most macrophytes regardless of temperature, at a higher rate than the redclaw crayfish or crabs. In contrast, redclaw crayfish consumed the most tilapia regardless of temperature, and targeted the tail, abdomen, and fins whereas the crab only consumed the head of the fish. The damage rates of redclaw crayfish were then combined with average mass of crayfish in three invasion cores in Zambia and Zimbabwe. It was found that the damage one crayfish may cause annual fishery losses from $6.15 (Kafue River); $5.42 (Lake Kariba); and $3.62 (Barotse floodplain).

Inland fisheries contribute substantially to the livelihoods and quality of life in Africa. The two invasive crayfish have different capacities for ecological and socio-economic impact depending on the resource and the temperature which means that impact assessments should not be generalised across species.

Redclaw crayfish capacity to damage fish catch was substantial but this should be caveated with two over/under estimation issues: 1) the potential for fisher behavioural change which may reduce crayfish damage and 2) small damage to the fish may render the catch unsaleable and therefore the cost of the whole fish is lost.

Dr Josie South states that while these data are a crucial first step in filling knowledge gaps in crayfish impacts in Africa, it also stresses the need to derive observed costs from fisheries dependent data to avoid misleading estimates.

Also of concern, is the capacity for ecological and socio-economic damage from the red swamp crayfish, which was recently removed from the NEM:BA regulations of prohibited species due to lack of impact evidence.

Read the paper published in NeoBiota

Madzivanzira TC, Weyl OLF, South J (2022) Ecological and potential socioeconomic impacts of two globally-invasive crayfish. NeoBiota 72: 25–43. https://doi.org/10.3897/neobiota.72.71868

This blog post was first published by DSI-NRF Centre for Invasion Biology, Stellenbosch University.

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Acta Ichthyologica et Piscatoria signs with Pensoft and moves to ARPHA

The scholarly publisher and technology provider Pensoft welcomes the latest addition to its diverse portfolio of scholarly outlets – the open-access, peer-reviewed journal Acta Ichthyologica et Piscatoria (AIeP), which publishes research in the fields of ichthyology and fisheries.

AIeP is an international scientific journal publishing articles in any aspect of ichthyology and fisheries concerning true fishes (fin-fishes), including taxonomy, biology, morphology, anatomy, physiology, pathology, parasitology, reproduction and zoogeography. The academic outlet, which was launched in 1970, favours research based on original experimental data or experimental methods, or new analyses of already existing data. AIeP is indexed by all major indexers, including Web of Science and Scopus. The journal’s first Impact Factor was released in 2010, and currently stands at 0.629 (2019).

The first 2021 issue of the the open-access, peer-reviewed international journal Acta Ichthyologica et Piscatoria is already online on a brand-new website

In joining the Pensoft portfolio, AIeP gets a brand-new user-friendly website with improved design and access to Pensoft’s self-developed full-featured platform ARPHA, which offers an end-to-end publishing solution from submission to publication, distribution and archiving. With features, such as papers available in semantically enhanced HTML and machine-readable XML formats, automated data export to aggregators, and web-service integrations with major global indexing databases, the easy-to-use, open-access platform ensures that published research is easy to discover, access, cite and reuse by both humans and machines all over the world.

AIeP’s first issue published with Pensoft features 14 scientifically diverse open-access articles on ichthyology and fisheries covering a wide geographic scope. Some of the issue’s most interesting reads explore the eating habits of the spotted rose snapper in the Gulf of California, offer the first underwater photograph of a rare scorpionfish in Japan, and record the first ever occurrence of the pharaoh cardinal fish in Libyan waters, in what constitutes the westernmost Mediterranean area of colonization of this non-indigenous species.

Amongst the published papers there are also practical suggestions for species conservation and sustainable fisheries management – for example, an evaluation of the size of freshwater fish in Bangladeshi wetlands recommends only harvesting fishes with a total length of over 8.80 cm.

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Additional information

About ARPHA:

ARPHA is the first end-to-end, narrative- and data-integrated publishing solution that supports the full life cycle of a manuscript, from authoring to reviewing, publishing and dissemination. ARPHA provides accomplished and streamlined production workflows that can be customized according to the journal’s needs. The platform enables a variety of publishing models through a number of options for branding, production and revenue models to choose from.

About Pensoft:

Pensoft is an independent academic publishing company, well-known worldwide for its innovations in the field of semantic publishing, as well as for its cutting-edge publishing tools and workflows. In 2013, Pensoft launched the first ever end to end XML-based authoring, reviewing and publishing workflow, as demonstrated by the Pensoft Writing Tool (PWT) and the Biodiversity Data Journal (BDJ), now upgraded to the ARPHA Publishing Platform. Flagship titles include: Research Ideas and Outcomes (RIO), One Ecosystem, ZooKeys, Biodiversity Data Journal, PhytoKeys, MycoKeys and many more.

Contacts:

Wojciech Piasecki, Editor-in-Chief at AIeP

editor@aiep.pl

Lyubomir Penev, founder and CEO at Pensoft and ARPHA

l.penev@pensoft.net 

Eco-certified Ashtamudi short-neck clam acquires its rightful identity

Fishermen fishing Ashtamudi short-neck clam.

Even though the short-neck clam is the major resource and export coming from Ashtamudi Lake in Kerala, India – the first fishery to be awarded with a a Marine Stewardship Council certification for sustainability in the country, a recent study found out that the mollusc had been subject to mistaken identity.

Further, this is not the first time when the species and genus name of this clam has been changed. At first, the species was identified as Paphia malabarica, which is also the name one could read in all hitherto published reports, including the Marine Stewardship Council’s register. Later on, as the name was proved to not be compliant with the current nomenclature, the Ashtamudi short-neck clam began to be referred to as Protapes gallus.

 Marcia recens from Ashtamudi lake, India.

However, the latest in-depth taxonomic study points to the clam having been misidentified from the very beginning. According to the finding of the team of A. Arathi, R. Ravinesh and A. Biju Kumar of the Department of Aquatic Biology and Fisheries, University of Kerala, and Graham Oliver of National Museum Wales, United Kingdom, the Ashtamudi short-neck clam belongs to a totally different genus, while its rightful scientific name actually is Marcia recens. Their paper was published in the open access journal ZooKeys.

Protapes gallus (Paphia malabarica) (above) and Marcia recens (below) showing obvious external morphological variations.

During their research, the scientists identified another edible species from Ashtamudi Lake that belongs to the Marcia genus: Marcia opima. While it could easily be mistaken for its commercially important relative thanks to a multitude of colour variations, it does not appear to contribute significantly to the export. Meanwhile, the actual species identified as Paphia malabarica (Protapes gallus) can be found in shallow coastal waters in the south of the country, but not in the studied brackishwater lake.

“No deleterious effects on the viability of the fishery have resulted from this error in identification, but from a legislative perspective applying the incorrect name to the exploited species could undermine its certification and protection,” comment the researchers.
“On the basis of this study, the species involved in the Marine Stewardship Council certification would be better considered at the generic level of Marcia or at the species level for Marcia recens, the most dominant species in the Ashtamudi Lake clam fishery zone.”

In conclusion, the authors of the study say that, “misidentification can undermine comparative biological studies and conservation, while more molecular studies are required to resolve the taxonomy of all clams involved in fishery.”

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Original source:

Arathi AR, Oliver PG, Ravinesh R, Kumar AB (2018) The Ashtamudi Lake short-neck clam: re-assigned to the genus Marcia H. Adams & A. Adams, 1857 (Bivalvia, Veneridae). ZooKeys 799: 1-20. https://doi.org/10.3897/zookeys.799.25829

Photos by Dr Biju Kumar.

How did the guppy cross the ocean: An unexpected fish appears on a volcanic archipelago

While people tend to describe tropical oceanic islands as ‘paradises on Earth’ and associate them with calm beaches, transparent warm waters and marvellous landscapes, archipelagos are often the product of a fierce natural force – volcanoes which erupt at the bottom of the sea.

Because of their origin, these islands have never been connected to the mainland, thereby it is extremely difficult for species to cross the ocean and populate them.DSCN1337

One such species – the South American guppy (Poecilia vivipara) – is a small freshwater fish which looks nowhere equipped to cross the distance between the mainland and the Fernando de Noronha oceanic archipelago in Northeast Brazil.

Nevertheless, the research team of PhD student Waldir M. Berbel-Filho and his professor Dr. Sergio Lima from Universidade Federal do Rio Grande do Norte recorded the species from a local mangrove on the island. The question that immediately sprang to the minds of the scientists was: ‘Where did the guppies come from and how did they get to Fernando de Noronha?’

To answer these questions, the scientists sequenced a gene of the guppies’ DNA to analyze potential signatures of the island colonization left in the fish DNA. As a result, they concluded that the isolated population was in fact closely related to the fish inhabiting the closest continental drainages.

However, this evidence was not enough to explain how the species turned up on the island in the first place. Was it natural colonization, or rather human introduction?

Poecilia vivipara Sergipe-2

The most likely scenario, according to the team, leads back to about 60 years ago when the American military had their WWII bases positioned at both Fernando de Noronha and Natal – the closest continental city. Indeed, the soldiers suggested to bring guppies to the island in an attempt to control mosquito population (in this region, guppies are commonly placed in water reservoirs to eat mosquito larvae).

On the other hand, natural dispersion cannot be completely excluded. The biologists remind that, apart for their exuberant colours and shapes, the guppies are well known for their capacity to resist to a wide range of environmental conditions. It could be that a set of circumstances occurring together, such as a favourable sea current, physiological adaptation and a bit of luck, might have brought the guppies to the archipelago.

Regardless of their means of transportation,” argue the authors, “this guppy population represents a valuable lesson on how small populations manage to colonize and thrive in isolated environments.

Despite being visited by thousands of people every year, some of the most intriguing secrets of tropical islands may still be hidden in the DNA of their inhabitants,” they conclude. “These ‘paradises on Earth’ are capable of simultaneously filling our hearts with beauty and our minds – with knowledge.”

 

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Original source:

Berbel-Filho WM, Barros-Neto LF, Dias RM, Mendes LF, Figueiredo CAA, Torres RA, Lima SMQ (2018) Poecilia vivipara Bloch & Schneider, 1801 (Cyprinodontiformes, Poeciliidae), a guppy in an oceanic archipelago: from where did it come? ZooKeys 746: 91-104. https://doi.org/10.3897/zookeys.746.20960