A slower pace of Life

Practical Fishkeeping (UK) - - Welcome - WORDS: GRE­GORY QUARTAROLLO

A creek in French Guiana yields a mul­ti­tude of characins, cat­fish and ci­ch­lids, along with some sur­pris­ing dis­cov­er­ies.

A creek in French Guiana yields a mul­ti­tude of characins, cat­fish and ci­ch­lids, along with some sur­pris­ing dis­cov­er­ies.

In Septem­ber 2015, five mem­bers of the Guyane Wild Fish So­ci­ety took part in an ex­pe­di­tion to Grand Laus­sat Creek, a trib­u­tary of the Mana River in French Guiana.

Ear­lier on this trip, we had vis­ited the rapids, char­ac­terised by shal­low wa­ters, rocky sub­strate, strong cur­rent and a wide and open sur­face al­low­ing aquatic plants to grow. Un­like the rapids habi­tat, this ‘creek’ biotope is dis­tin­guished by a deeper and nar­rower body of wa­ter (one me­tre deep on av­er­age and just a few me­tres wide), sandy sub­strate, slow cur­rent and sig­nif­i­cant for­est cover lim­it­ing the growth of aquatic plants.

The banks show signs of strong ero­sion caused by floods. In the rainy season dur­ing the floods the cur­rent is stronger and the wa­ter level more than 2m higher than the cur­rent dry season level, with a sub­stan­tial plant lit­ter layer along the edges. Logs or fallen trees are all around, some­times over the en­tire width of the creek. In the creek, the plant Thur­nia

sphae­ro­cephala is present in two dif­fer­ent forms — a young, aquatic stage and an adult stage which is ter­res­trial (with its base al­ways near or un­der­wa­ter). The ter­res­trial form pro­duces flo­res­cence in the dry season and is adapted to sev­eral months of im­mer­sion in the rainy season. Un­less you know dif­fer­ent, you would as­sume they are two dif­fer­ent species.

The ‘creek biotope’ com­mu­nity

Many kinds of fish oc­cur in the creek. The Characi­forms are the dom­i­nant group (around 80 species) with tetras in­clud­ing Hem­i­gram­mus boes­mani, Hyphes­so­brycon copelandi, Moenkhau­sia col­let­tii and Bryconops cau­do­mac­u­la­tus. They are to be found all around but usu­ally not school­ing.

My­lo­plus ter­netzi, a small cousin of the Pacu, is also found here in its ju­ve­nile stage; the adults live in the main river.

Characid­ium ze­bra, a bot­tom dwelling fish, is found on the sand or among the plant lit­ter. These fish ap­pear to walk on the sub­strate prey­ing on lit­tle aquatic bugs that we can­not even see.

An­other, smaller, mem­ber of the Crenichi­dae fam­ily is here:

Me­lanocharacid­ium dispi­lomma is an in­ter­est­ing lit­tle fish of­ten seen sit­ting atop a log. It is small, blends into its sur­round­ings, and is usu­ally mo­tion­less but ca­pa­ble of dis­ap­pear­ing quickly, mak­ing it quite in­con­spic­u­ous. It’s also re­ally hard to catch, which is why we still don’t have a photo of it in a field tank.

Some Cyphocharax hel­leri, eas­ily recog­nis­able by the zigzagged lon­gi­tu­di­nal lines on their flanks, are typ­i­cally swim­ming in small groups, feed­ing on biofilm by sift­ing sand or graz­ing on plant lit­ter. They are mem­bers of the Curi­mati­dae fam­ily, an im­por­tant source of food for many preda­tors and even peo­ple liv­ing along the rivers. Many species of this fam­ily look like barbs from Asia.

Unseen hunters

In ar­eas of deeper wa­ter, we hear a big splash from time to time. There are def­i­nitely some fish hunt­ing — maybe

Ho­plias aimara or H. mal­abar­i­cus chas­ing some small fish like Bryconops or

Cyphocharax. They might also be Brycon gulp­ing flow­ers or seeds float­ing on the sur­face. But we all have our heads un­der­wa­ter, snorkelling and ob­serv­ing small fish, and the high con­cen­tra­tion of tan­nins in the wa­ter and the poor quan­tity of light reach­ing the creek does not al­low us to see what’s re­ally go­ing on and who is mak­ing the noise.

The colour of Rinelori­caria aff. stew­arti re­sem­bles sticks or shad­ows on the sand. On a log or leaf, they’re more ex­posed, but they blend in so well against the sub­strate or leaf lit­ter that it’s a chal­lenge to find one.

Grand Laus­sat creek.

Hem­i­gram­mus boes­mani.

Bryconops cau­do­mac­u­la­tus.

Characid­ium ze­bra.

My­lo­plus ter­netzi.

Cyphocharax hel­leri.

Me­lanocharacid­ium dispi­lomma.

Rinelori­caria aff. stew­arti.

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.