Due to the historical isolation of Antarctic wildlife, they are easily outcompeted and threatened by introduced species, also brought by human activity.[37] Many introduced species have already established themselves,[9] with rats a particular threat, especially to nesting seabirds whose eggs they eat.[37] Illegal fishing remains an issue,[13] as overfishing poses a great threat to krill and toothfish populations. Toothfish, slow-growing, long-lived fish that have previously suffered from overfishing, are particularly at risk. Illegal fishing also brings further risks through the use of techniques banned in regulated fishing, such as gillnetting[38] and longline fishing.