Running out of ideas for production techniques, Underscores challenged herself to play the guitar on every song of the album as she had little experience with the instrument.

The album is characterized by glitchy production, distorted guitars, and pitched-up vocals, discussing celebrity culture in its lyrics.

It also was received positively by high-profile musicians; the album allowed Underscores to tour with Glaive and Ericdoa and book studio sessions with 100 gecs and Travis Barker.

[6] Underscores described her experience of contacting 8485 to appear on Fishmonger as difficult because she highly respected 8485 and "thought she was a larger than life person".

[10] The Fader's David Renshaw felt it contained influences of pop-punk and electronic music and was "branded as hyperpop",[11] while Colin Joyce of the same magazine called it an "album full of digi-punk contortions".

[12] Matthew Kim from The Line of Best Fit said the album "cycled through hyperpop, garage punk, emo rap, dubstep and psychedelic ambience like it was nothing".

[10] NPR's Reanna Cruz said the album is "equally digicore as it is emo" and draws from SoundCloud rap and the music from Spotify's "Lorem" playlist.

[7] It is followed by "Second Hand Embarrassment", an indie pop track that combines whispered vocals and an electronic instrumental with "bubbly" 808 drums.

[12] An alt-rock track,[17] "Kinko's Field Trip 2006" contains pitched-up vocals over an energetic chorus and distorted guitars.

[5] It starts with acoustic guitars and fretful lyricism; it has a standard pop-punk song structure that delves into an electronic downtempo beat.

[7][20] It begins as an electropop song that loses its momentum, incorporating guitars that create an atmospheric fusion of dream pop and shoegaze.

[4][5] The Norwegian musician and record producer Lido found affinity with the album and sent it to his manager, Jackson Perry, who then sent it to his coworker, Dorothy Caccavale.

[5] Due to the success of Fishmonger, Underscores was able to tour with Glaive and Ericdoa and be invited to studio sessions with 100 gecs and Barker.

[11] The song "Uncanny Long Arms" from her next album, Wallsocket (2023), adapts the power pop guitar climax of "Kinko's Field Trip 2006".

[9] He further expressed that the album "sounds like an expertly produced band with a record deal" and not an independent musician making music in their parents' house.

[12] The same magazine also included "Spoiled Little Brat" in their list of "The best rock songs right now" in May 2021; Renshaw considered it a standout from the album and said it "contextualises [Underscores] a little better".

He concluded by describing Fishmonger as "fun, accessible, detailed, and impeccably written" with the ability to mix hyperpop with unexpected genres and sounds.

[16] Elias Light for Rolling Stone deemed "Where Did You Fall" a standout track and described "Your Favorite Sidekick" as "shattering".