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In Other Words

March 14
Benthos

​Silvana Birchenough Chair of the the ​​​Benthos Ecology Working Group (BEWG)​ and the Steering Group on Ecosystem Processes and Dynamics (SSGEDP)​​​​

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'The concept of 'benthos is used to refer to organisms or a community of organisms that live on, in, or near the seabed, also known as the benthic zone. Depending on their size, they can be classified into macrobenthos (greater than 1 mm), meiobenthos (less than 1 mm but greater than 0.1 mm) or microbenthos (less than 0.1 mm). There are also different types that can be classified into zoobenthos (all benthic organisms) and phytobenthos (including benthic diatoms and macroalgae or seaweed). 

Benthic organisms are important, as they play a key role in marine ecosystems, helping to deliver many ecosystem goods and services, ranging from biodiversity, remineralization of nutrients, long-term carbon storage and provision of food for high trophic levels. These are just some main activities fueled by the benthic system. There are many more.'

March 06
Fishery-dependent and fishery-independent information

​​​​Mike Armstrong, co-chair of the ​​Benchmark Workshop for Sea Bass (WKBASS)

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'ICES provides advice each year on the state of fish stocks in European waters, as well as options for future fishing opportunities in line with the principles of sustainable fishing. Where does ICES obtain the evidence to support its advice? Fish, invertebrates and their predators are largely out of sight below the water surface and it is clearly impossible to count and measure all the individuals in the population. We must sample the population to find evidence for changes that are taking place. The main sources of data are from the fisheries themselves and from sampling programmes independent of the fisheries.

Fishery-dependent data include mandatory data on catches and fishing activities supplied by fishing skippers, as well as representative sampling of fishing trips to estimate discarded and recreational catches not reported through logbooks. In some fisheries, the trends in quantities caught per unit of fishing effort (e.g. per day) can provide evidence on trends in stock abundance. Sampling on shore and at sea provides information on the size and (where possible) age of individuals in the catches. These data can be used to estimate the annual fishing mortality rate, an indicator of the proportion of the stock removed by fishing during the year which can be compared with values considered sustainable.

Fishery-independent data are collected, for example, from research vessels using trawls, acoustic systems, underwater cameras and planktonic egg samplers to collect data on abundance and composition at stations or transects positioned randomly or systematically across the geographic range of the stock. Many such surveys also provide other data on the ecosystem. Fishery-independent data can be used on their own to provide advice on stock trends, but ICES often includes them with fishery-dependent data in assessments to provide the most accurate estimates of stock trends, stock status and future fishing opportunities.'

September 23
Non-indigenous species and ballast water in Canadian Arctic

​Masters student Pascal Tremblay of the Université du Québec à Rimouski, Canada, exlplains his poster 'Assessment of nonindigenous species introduction risk through ballast water discharge of a domestic ship in the Canadian Arctic'.

 Pascal's co-authors are André Rochon, Gesche Winkler, Kimberly Howland, Nathalie Simard, and Sarah Bailey.

September 23
Aged and children first!

Masters student Stefanie Haase tells us about her Annual Science Conference poster 'Aged and Children first!' about challenges in the development of a new selectivity concept for trawl fisheries.

Stefanie's co-authors are Juan Santos, Annemarie Schütz, Bernd Mieske, and Daniel Stepputtis.

See high quality poster here

September 23
What's on cod's menu?

Nataliia ​Kulatska from the Swedish University of Agricultural Sciences explains her Annual Science Conference poster 'what's on cod's menu?' about the fisheries effects on the interactions between species as well as on their population dynamics and size structure.

Nataliia'a co-authors are: Valerio Bartolino, Håkan Wennhage, Bjarki Elvarsson, and Gunnar Stefansson.

See the poster in high quality here  

June 24
Upwelling

​Kai Myrberg, ​​​Vice-President of ICES Bureau​.

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'Upwelling is a procedure which happens in the sea, where cold and nutrient-rich water comes up from the layers below the surface. In such a case there is enrichment of the biological activity and processes. There are a lot of nutrients which means there are also a lot of fishes to eat the plankton that is available. It couples physical and biological processes in fisheries, so in this respect it's important.'​

June 23
Trophic interactions

Bill Karp, Vice-President of ICES Bureau.​​

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​'Trophic interactions are all about who eats whom. It's based on this idea of a trophic pyramid, where there are different levels – called trophic levels. The lowest level contains plants, phytoplankton. Then the next level, which is the first level of consumers, contains small animals that eat plants. Then as you get higher and higher you get bigger animals, fish, and marine mammals that are less dependent on plants and more dependent on bigger and bigger animals.

It's important because these interactions amongst animals and plants that are eaten or eat characterize the ecosystem, and we have to try really hard to understand quantitatively what the energy flow is across these different levels and what the mortality is associated with consumption, which then is part of natural mortality, which is an input into stock assessment models, or in a more complex way because of all these interactions into ecosystem models.'


June 22
Pelagic

President of ICES Bureau​​ Cornelius Hammer.

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'Normally pelagic is perceived as the open water. When you leave the coast, you cross water that is about 100-200 metres deep – the continental shelf – and then you are out in the open sea. What's underneath you is pelagic. The seemingly unstructured open water without boundaries. However, it is structured. We normally can't perceived this though. For the plankton that floats through the pelagic area and the fish that swim through it or drift with the currents, it is very structured. There are different water bodies and also movement of these horizontally and vertically.

There are areas where deep water rises, brining nutrients to the surface. With these nutrients there is diverse and productive life, which attracts predators. So in the middle of a seemingly uniform environment you find hotspots of life; other areas are pretty empty. Often you have huge visibility with little light. We call it the 'desert of the ocean'. It seems to be clear water, but from the perspective of an animal or plant in the environment it is a desert. Most of the pelagic is this clear water, but not all of it. There are huge horizontal and vertical movements; for instance in the pelagic North Atlantic, this is very productive, the water isn't that clear. The desert storms from the Sahara bring dust clouds which precipitate and fertilize the area with iron. This helps phytoplankton life and makes the water green and non-transparent. That again is the basis of zooplankton growth and then fish and mammals.

Between the Faroes and Iceland there is a huge barrier and the water from the north floats over at 200 metres deep over this barrier and falls down to three thousands metres. So there's a waterfall within this vast pelagic area. There's a lot of physical and biological activity going on in the pelagic environment, it's not just a uniform environment.'​

May 26
Backscatter

​​James Strong, Chair of the Working Group on Marine Habitat Mapping (WGMHM)

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'In marine science, backscatter typically refers to the reflection of soundwaves back towards their source. This reflectance is usually measured as an acoustic intensity (at a known reference angle). The time delay between a soundwave being emitted, bouncing off a seabed or mid-water object, and being received provides a measure of range (e.g. depth) – this principle forms the basis of 'sonar' (SOund Navigation And Ranging). 

The emitted soundwave also loses intensity through scattering as it travels – this is detectable as acoustic backscatter. Particles in the water column partially scatter the soundwave but the majority this occurs at the seabed. The scattering is influenced by the size, shape and composition of the seabed. This information is extremely important for estimating the nature of the seabed and predicting the seabed habitats present. As such, marine habitat mapping surveys use sophisticated 'side-scan' and 'multi-beam' sonars to collect both range (depth) and backscatter (seabed texture and likely composition) simultaneously.'​

May 12
Fishing gear selectivity

Pingguo He and Petri Suuronen, chairs of the Working Group on Fishing Technology and Fish Behaviour WGFTFB)​​

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'The phrases "fishing gear selectivity", "selective fishing", and "selection of fish" by a fishing gear are widely and sometimes interchangeably used in fisheries science and management.  However, they are poorly defined, causing confusion even among professionals on the subject. Our working group provided the authoritative definition of selection and selectivity in 1996:

"Selection of fish by a fishing gear can be considered to be the process which causes the catch to have a different composition to that of the fish population in the geographical area in which the gear is being used. The selectivity of a fishing gear is a measurement of the selection process."

We can define "selective fishing" as the ability to target and capture specific types of marine organisms, allowing unwanted sizes and species to evade or escape capture. Selective fishing may be a result of intentional measures associated with gear design or operational tactics or unequal vulnerability of different sizes and species of marine organisms to the gear.

Size selectivity is the ability of fishing gears to target and retain certain sizes of organism within a species. Size selection covers all processes that cause the probability of capture to vary with fish size. Size selectivity is used to control the impact of fishing on juveniles through the regulation of codend mesh sizes or other devices and designs. With size selective fishing, the age at first capture is typically increased to increase total yield from the stock.

Species selectivity is the ability of fishing gears to target and retain certain species, and less so for other species. Methods that improve species selectivity allow fishers to catch and retain desired target species more efficiently, while reduce the amount of non-target species, often called bycatch species. Species selectivity can be achieved through a range of modification in gear design and operation, and the knowledge of fish behaviour is often fundamental in this development.​'​


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In Other Words is a blog devoted to clarifying some of the important terms and phrases that are crucial to the work we carry out as well as the wider world of marine science.

Each week we'll feature a scientist or expert from one of our working groups, who will explain a term relevant to their efforts In Other Words.

Stay tuned!