BE­HAV­IOR OF “IN­VA­SIVE” KNIFEFISH RE­VEALED

Agriculture - - Pest Studied -

THE UNIVER­SITY of the Philip­pines Los Baños (UPLB) Lim­no­log­i­cal Sta­tion pub­lished a tech­ni­cal bul­letin ti­tled “Bi­ol­ogy of Knifefish ( Chi­tala or­nate) in La­guna de Bay” to help fish­er­folk and the gen­eral pub­lic un­der­stand the bi­ol­ogy, be­hav­ior, and move­ment of this in­va­sive species.

Ac­cord­ing to the bul­letin, knifefish ex­hibits sea­sonal spawn­ing, with March-May as the peak pe­riod. The par­ent fish cre­ates a nest or pit around the bam­boo pole where the eggs are at­tached and one or both par­ents guard the nest un­til the eggs are hatched. The parental care en­sures that most of the eggs sur­vive which con­trib­utes to their re­pro­duc­tive suc­cess.

Phys­i­cal re­moval such as har­vest­ing and over­fish­ing are ef­fec­tive in con­trol­ling the knifefish pop­u­la­tion. How­ever, con­trol by har­vest­ing can be

most suc­cess­ful prior to spawn­ing and dur­ing school­ing of ju­ve­niles.

In terms of move­ment, large knifefish (50-75 cen­time­ters (cm)) can travel 1.1 kilo­me­ters in less than 24 hours while smaller ones (19-29 cm) usu­ally travel at shorter dis­tances. Adult knifefish tend to stay near fish­pens, while smaller ju­ve­niles usu­ally stay near land ar­eas with sub­merged veg­e­ta­tion ( Val­lis­ne­ria sp. com­monly known as eel­grass).

The stom­ach con­tent of knifefish shows that small-sized fish feed pri­mar­ily on shrimp such as ‘yapyap’ and ‘hipon’, while large-sized fish feed more on fishes. Based on their feed­ing be­hav­ior, baited fish­ing meth­ods such as ‘ki­tang’ (long­line) is ef­fec­tive for catch­ing. The rec­om­mended sched­ule for catch­ing is from 4 to 7 am or 7 to 10 pm, the pe­riod which co­in­cides with their feed­ing.

The bul­letin is an out­put of the Philip­pine Coun­cil for Agri­cul­ture, Aquatic and Nat­u­ral Re­sources Re­search and De­vel­op­ment (PCAARRD)-funded Re­search and De­vel­op­ment (R&D) pro­gram “To­wards the Con­trol and Man­age­ment of the In­va­sive Knifefish in La­guna de Bay.” (LOUREEDA C. DARVIN, PCAARRD FARMNEWS) ( Photo credit: BEDO (Thai­land) - Own work, CC BY-SA 4.0, https://com­mons.wiki­me­dia.org/w/in­dex.php?curid=40262576)

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