Blog post

Joe Freijser: Calm start and the deep sea

Published on
March 30, 2012

The start of this Blue Whiting survey has so far been very comfortable, as we have experienced extremely good weather.

Blue Whiting has been abundant, 4 out of 5 hauls contained ‘reldel’ catches! This is Dutch fishermen's jargon indicating a clean catch of purely target fish.

For my personal research on the mesopelagic fish (‘deep sea fish’) assemblages these catches are less interesting because so far they contained relatively few species that I can use.

Blue Whiting is also a mesopelagic fish species, but my focus lies more with the non-commercial bycatch of lanternfish, hatchet fish and small deep sea predators like the viper fish.

The mesopelagic is also known as the twilight zone and ranges from a depth of 200 m to 1000 m, at these depths light penetrating from the surface is very weak and many species of fish, squid, shrimp and even jellyfish have developed light organs. These light organs are believed to be used for communication, attracting prey and confusing or hiding from predators.

Especially haul 4 had a great abundance of mesopelagic fish species, and very few Blue Whiting, this seems to indicate that the abundance of smaller mesopelagics tends to be less around schools of Blue Whiting. Of about 20 deep sea species caught during this trawl in total, two were new to our catch list (http://www.7seas-outreach.com/wiki/index.php/Category:Species). This means that slowly the photo database of deep sea fish species caught during this survey is growing. I am looking forward to looking at more strange deep sea fish that are caught together with the Blue Whiting hauls and especially the dedicated deep sea hauls that will be done later next week at depths of around 1000m.

Lanternfish eating a silvery lightfish
Lanternfish eating a silvery lightfish
Entity of mesopelagics contained within haul number 4
Entity of mesopelagics contained within haul number 4
Blauwkeel Roodbaars
Blauwkeel Roodbaars

New to our deep sea guide:

Barracudina spp.
Barracudina spp.
Barracudina spp.
Barracudina spp.
Diaphus metopoclampus
Diaphus metopoclampus
Diaphus metopoclampus