Croaker

Paralonchurus peruanus is a fish of the family Sciaenidae, described by Steindachner in 1875 under another genus name, Genyanemus ^[1]. In Peru the fishery studies call it suco ^[2]. It lives on the bottom of sandy coasts, and the studies reviewed describe it as carnivorous, with a preference for polychaete worms ^[3]. It is caught with curtain nets and sold fresh for human consumption ^[2]. Its global category on the IUCN Red List is Least Concern ^[4].

It has an elongated, slightly compressed body with an arched back and a small mouth set below the snout; the chin carries small barbels, 12 to 15 pairs, plus 5 pores ^[5]. The colour is dark silvery, with 7 or 8 faint bars on the flanks and dark fins ^[5]. Other authors describe the sides as silvery, with or without dark bands ^[2].

The maximum recorded size is 51 cm total length, and a common size is about 30 cm ^[5]. In 1,803 fish landed in La Libertad between May 2011 and April 2012 the lengths ranged from 18 to 51 cm, with a mean of 26.8 cm and a mode of 24 cm; 88.5 % were juveniles ^[3].

FishBase places it in the Eastern Pacific, from Panama to northern Chile ^[5]. An IMARPE study, following the 2001 catalogue of marine fishes by Chirichigno and Cornejo, places it in warm and temperate waters between Puerto Pizarro, in Peru, and Arica, in Chile ^[2].

It is a benthopelagic fish of sandy and muddy-sand coastal bottoms, also near estuaries ^[2]. FishBase classifies it as demersal on sandy coasts and bays, from about 10 m depth ^[5].

The fish studied in La Libertad in 2011-2012 showed sexual maturity stages II to VII in both sexes, and only the females showed stage VIII; the species spawns all year round, with more activity in late summer and autumn ^[3]. The weight-length relationship followed a power curve with an exponent close to 3 (2.98 in females and 2.97 in males), which indicates negative allometric growth ^[3].

In growth, females reached an asymptotic length of 53.68 cm with K of 0.22 per year, and males 53.28 cm with K of 0.21 per year; 6 age groups were distinguished in females and 7 in males ^[3]. Growth is fast during the first 3 years and then slows; females grow larger than males ^[3]. Condition factor was best in June and October in both sexes ^[3].

It is carnivorous and feeds mainly on invertebrates of the seabed. In 354 full stomachs from fish caught in La Libertad in 2016, 18 prey were recognised from 6 phyla, and the most important was the polychaete Pherusa sp., with 41.2 % of the relative importance index ^[2]. In the 2011-2012 sample polychaetes made up 68.53 % of the weight of the food, followed by ophiuroids, molluscs and crustaceans, and fish came last ^[3].

The diet changes with month and with size: the ophiuroid Ophiactis sp. predominated in fish smaller than 31 cm, and in August 2016 the crustacean Emerita analoga («muy muy») predominated ^[2]. Many stomachs were empty: the vacuity index was 27.1 % in August and 77.5 % in October ^[2].

Its global category on the IUCN Red List is Least Concern ^[4]. Small-scale fishing takes it regularly: between May 2011 and April 2012 about 191 thousand kilograms were landed in La Libertad ^[3].

The authors of that study note that the suco fishery has been affected by climate and by overexploitation, and in their analysis the catch per unit of effort fell as standardized effort rose ^[3]. Since almost 9 in 10 fish measured were juveniles, pressure on small sizes is a question those data leave open ^[3].

It is highly valued for its meat, which is sold fresh for direct human consumption ^[2]. FishBase adds uses in commercial fisheries and in the aquarium trade ^[5].

Between May 2011 and April 2012, landings in La Libertad were split among Pacasmayo (45.1 %), Chicama (27.2 %), Puerto Morín (20.0 %), Salaverry (6.4 %) and Huanchaco (1.3 %) ^[3]. Boats contributed 82.6 % of the volume and the curtain net was the most used gear; purse seine, beach seine, trammel net and hook line were also used ^[3].

The literature reviewed records the suco in small-scale fishery catches in La Libertad, not in diving observations. The fish of 2016 came from 16 fishing areas between Punta Chérrepe and the Santa river, and were caught with curtain nets ^[2]. In 2011-2012 the largest landings came from areas such as Huaca Blanca, Puémape and Chérrepe, on the same coast ^[3].