▁water ways , ▁such ▁as ▁the ▁Elizabeth ▁River ▁in ▁Virginia ▁and , ▁in ▁New ▁Jersey , ▁the ▁H ack ens ack ▁River ▁and ▁the ▁Arthur ▁Kill . ▁A ▁ 2 0 0 8 ▁Virginia ▁Institute ▁of ▁Marine ▁Science ▁report ▁stated ▁that ▁ 3 8 % ▁of ▁m umm ich ogs ▁from ▁Elizabeth ▁River ▁had ▁cancer ous ▁les ions , ▁and ▁" more ▁than ▁half ▁had ▁pre - can cer ous ▁les ions . ▁That ▁was ▁largely ▁due ▁to ▁high ▁levels ▁of ▁poly cyc lic ▁a rom atic ▁hydro car b ons ". ▁ ▁Kill if ish ▁eggs ▁are ▁used ▁in ▁development al ▁studies ▁and ▁when ▁teaching ▁emb ry ology ▁because ▁the ▁eyes , ▁the ▁be ating ▁heart , ▁and ▁the ▁different ▁stages ▁of ▁ont ogen esis ▁can ▁be ▁easily ▁exam ined . ▁Emb ry os ▁are ▁also ▁extremely ▁dur able ▁and ▁easy ▁to ▁manipulate ▁in ▁the ▁labor atory . ▁ ▁M umm ich ogs ▁were ▁the ▁first ▁fish ▁sent ▁to ▁space . ▁In ▁ 1 9 7 3 ▁a ▁couple ▁of ▁them ▁were ▁flow n ▁in ▁a ▁pl astic ▁bag ▁aqu arium ▁ab o ard ▁Sk yl ab , ▁during ▁the ▁Sk yl ab ▁ 3 ▁mission . ▁In ▁the ▁absence ▁of ▁gravity ▁the ▁fish ▁at ▁first ▁exhib ited ▁an ▁unusual ▁sw imming ▁behavior : ▁they ▁constantly ▁pitch ed ▁forward ▁and ▁therefore ▁described ▁tight ▁circles . ▁However , ▁by ▁day ▁ 2 2 ▁of ▁the ▁mission ▁they ▁sw am ▁normally . ▁Fif ty ▁eggs ▁at ▁an ▁advanced ▁stage ▁of ▁development ▁had ▁also ▁been