[5] Some research has occurred on the problems caused by this species in aquaculture, but little is known about the salmon louse's life in nature.

[7] When aquaculturalists place their post smolts into sea water, they are commonly known to be ectoparasite free, and this can last for many months.

Newly hatched larvae do not survive below salinities of 15‰ and poor development to the infective copepodid occurs between 20 and 25‰.

Nauplii and copepodids are positively phototactic and exhibit a daily vertical migration, rising during the day and sinking at night.

Finding their migratory hosts in the vastness of the ocean is still a mystery for scientists to solve, but the species has managed to do this effectively for millennia.

[11] Sea lice can also attach to juvenile salmon migrating from rivers to the ocean if they pass by fish farms.

[12] In 2016 Guardian news stated that the lice killed thousands of tonnes of farmed fish, caused skin lesions and secondary infections in millions more, and cost the Scottish salmon industry around £300m in control efforts.

CRISPR is characterised as a GMO light method, since it does not necessarily mean that a new gene is introduced, it may for instance only have been repaired, if a harmful mutation has occurred.

In several countries (e.g. USA, Canada and Brazil), genetically modified fish is allowed to be sold as food today.

In Norway, CRISPR has only been used in research so far, and genetic modification is strictly regulated by the Gene Technology Act.

The challenge is that lice resistance has a polygenic inheritance, and a low-to-moderate heritability, but with CRISPR technology we have the opportunity to go beyond the existing alleles and genome of the Atlantic salmon and use genomic material from for instance coho or pink salmon, which show almost complete lice resistant.

The parasites can cause physical damage to the fish's fins, skin erosion, constant bleeding, and open wounds creating pathways for other pathogens.

Disruption of ionic homeostasis in pre-mature smolt stages can result in reductions in growth rate, limit swimming capabilities, and even death.

Disturbances in hydro mineral balance can result in negative consequences at the cellular, tissue, and organism levels.

High levels of salmon lice infections result in a weaker ion regulation system.

Intensity is determined by recognition of and regulation by salmon lice secretory/excretory products (SEP), which include proteases and prostaglandin E2.

The marine parasite secretes SEP into the damaged skin of the salmon which inhibits proteolytic activity.

Proteolytic activity increases the amount of host peptides and amino acids that can be used as a source of nutrition and lowers the intensity of inflammatory responses.

Two cytometric techniques, flow cytometry (FCM) and Feulgen image analysis densitometry (FIAD), gave measurements of 1.3–1.6 Gigabase pairs (Gb) in the haploid genome corresponding to a nuclear DNA weight of 1.35-1.61 picograms (pg) with differences between sexes.

The most plausible explanation for this discrepancy may be that repetitive elements cause sequencing approaches to underestimate genome size[25] as reported for beetles (Coleoptera).