Rio Curicuriari Sport Fishing Report

Rio Curicuriari - 2019 Sport Fishing Report and Analysis

By Paulo Petry and Paul Reiss

Introduction - The objective of this report is to characterize the impact and sustainability of the sport fishing activity conducted in the Curicuriari River using data obtained during the 2019 fishing season between September and November. The data, recording hydrological parameters, fishing effort and angler catches of the two species targeted by sport fishermen was collected by Acute Angling’s guides and fishing personnel according to a research plan and experimental design generated by ichthyological researchers Paulo Petry, PhD and Paul Reiss, PhD. This report was originally developed to meet a governmental reporting requirement and is presented here translated from the original Portuguese.

Description of the fishing area

The Rio Curicuriari - Located in the upper Rio Negro basin in Amazonas State, the Rio Curicuriari is a major tributary of the upper basin’s right-hand region, located just downstream of Camanaus, near São Gabriel da Cachoeira. Like other Rio Negro tributaries in this region, the Curicuriari is a heavily tannin-stained blackwater river, with a high load of dissolved organic acids and low suspended sediment load. The river cuts through granite outcroppings of the Guyana shield in the lower 80 kilometers of its channel (between the Indigenous community of Tumbira and the confluence with the Rio Negro). This section of the river has a significant gradient, with strong current, mostly shallow depth and several stretches of substantial rapids in its rocky bed, (figure 1). The marginal vegetation in this area is formed by “terra firme” forest. Above Tumbira, the river undergoes a transformation; its gradient decreases dramatically and it takes on the characteristics of the slow-flowing, flood-plain remnant fisheries familiar to peacock bass anglers. In this upper region, the river channel cuts through alluvial sedimentary formations, composed of fine-grained sandy deposits, and changes into a meandering conformation, featuring a broad floodplain with many lakes and abandoned floodplain remnants. The floodplain conformation extends over 275 kilometers, to the headwaters of the river, formed by the confluence of several smaller, faster-moving streams. Due to the easy natural erosion of these alluvial deposits, the riverbed is subject to constant lateral migrations, forming large sandbars, beaches, complex meandering lakes and “ressacas”. This vicariant geomorphic behavior generates great heterogeneity of habitats and environmental conditions that serve to define the aquatic ecosystem of the upper river system and provide ideal conditions for a rich fauna of fish of various sizes. The marginal vegetation upstream of Tumbira is dominated by low-height meadows, igapó and “campinas” typical of tributaries on the right (southern) bank of the Rio Negro (figure 2).

peacock bass water
Figure 1. Bed of the lower portion of the Rio Curicuriari, where it has carved through the granitic/quartzite underlayment of the Guyana shield, surrounded by terra firme forest vegetation. The Blackwater Adventurer, with the help of our fishing boats and Indian guides must navigate this section in order to reach the peaceful waters of the floodplain fishery.
The upper portion of the Rio Curicuriari
Figure 2. The upper portion of the Rio Curicuriari, where the riverbed meanders through sandy sedimentary deposits surrounded by “igapó” vegetation. These still waters provide a wide range of giant peacock bass habitat

Target Species - The sport fishing target species in the Rio Curicuriari are Cichla temensis (the giant peacock bass — figure 3(A) in paca form and figure 3(B) in açu form) and Cichla orinocensis (figure 3, the “borboleto” or butterfly peacock bass). Cichla temensis is encountered in two forms; 3(A) - tucunaré paca – individuals of either sex not actively involved in reproduction or rearing of juveniles, 3(B) tucunaré açu – individuals actively involved with the spawning cycle or rearing of juveniles. This color and pattern variation was first described by Reiss, et al, in 2011.

Figure 3. (A) - tucunaré paca (C. temensis)
Figure 3. (A) - tucunaré paca (C. temensis)
Figure 3. (B) - tucunaré açu (C. temensis)
Figure 3. (B) - tucunaré açu (C. temensis)

Cichla orinocensis does not cycle through this type of dramatic cyclical change, however, like many fishes, their coloration becomes more intense during the spawn.

Figure 3. (C ) – Butterfly Peacock - Tucunaré borboleta (C. orinocensis)
Figure 3. (C ) – Butterfly Peacock - Tucunaré borboleta (C. orinocensis)

Defined Fishing Areas - The most productive fishing areas for these two species are determined by the presence of the specific type of habitat where these species tend to occur in greatest abundance. Therefore, the fishing area was focused on the region upstream of Tumbira where the riverbed has a flatter gradient, the current speed is lower and many lakes and “ressacas” associated with the river’s floodplain occur. The total fishing area consisted of 275 km of the upper Rio Curicuriari and its associated tributaries and floodplain structures, divided into 4 fishing zones which were rotated during the fishing period (Figure 4):

  • zone 1; upstream from Tumbira to the mouth of the Rio Capauari tributary, with 25 km of main river channel and braids and great density of floodplain remnant structure;
  • zone 2; from the Capauari to the mouth of the Rio Miriti tributary, with 45 km of main river channel and significant concentration of floodplain remnant structure;
  • zone 3; from the Miriti to “Chapéu do Cozinheiro” with 85 km of river and moderate concentration of floodplain remnant structure;
  • zone 4; from “Chapéu do Cozinheiro” to the “Repartimento” with 120 km of river and sporadic concentration of floodplain remnant structure.

These 4 zones were defined with the goal of maintaining a balance between (a) the mechanical logistics necessary to provide productive fishing; (b) to enable utilization of the area with optimal conditions at any given time during the river’s natural water level oscillations within its low water period; and (c), to establish fishing rotation areas so as not to concentrate fishing effort in any specific part of the river.

Figure 4. Location of the Curicuriari River and delimitation of fishing areas.
Figure 4. Location of the Curicuriari River and delimitation of fishing areas. Note that regions are progressively longer as they extend upriver, to accommodate the reduced surface area of river and floodplain remnants in the smaller waters upriver. The lower areas include two major tributaries providing additional fishing area and water inflow.

Description of fishing activity

Techniques - Sport fishing activity on the Rio Curicuriari River uses the same fishing modality practiced in other areas of the Rio Negro basin. The fishery, entirely enclosed within an Indian reservation is contractually and governmentally limited to exclusive access by Acute Angling, in partnership with the Indigenous community. Acute Angling’s Blackwater Adventurer Floating Hotel operation hosted groups limited to 8 fishermen (or less) who fished for 1 week and were then replaced by a new group the following week. The fishing was carried out from fully-equipped aluminum bass boats manned by a professional guide, a member of the indigenous community (being trained as an apprentice guide) and 2 sport fishermen. A maximum of 4 fishing boats with this configuration operated during the fishing period.

Equipment - Anglers are provided with a full suite of modern, high-quality fishing gear and the appropriate lures, including;

  1. A carbon-fiber Okuma medium-light spinning rod matched with a Shimano Stradic 2500 spinning reel and strung with 30 pound-test Power-Pro braided line, primarily for use with smaller lures and the ubiquitous “Peacock bass rattle jig”.
  2. A carbon-fiber Okuma medium-heavy baitcasting rod matched with a Shimano Curado 200 baitcasting reel and strung with 65 pound-test Power-Pro braided line, primarily for use with larger sub-surface lures and the popular propeller-type surface lures.
  3. A variety of artificial lures including peacock rattle jigs, propeller lures, walking stick baits and subsurface swimming plugs.

Fishing tactics and implementation - Gear and lure choice are selected either by the fishermen or the recommendation of the guide, and generally dependent on fishing location, ambient conditions and angler capabilities. The guides select fishing sites based on their knowledge of the target species' behavior, river conditions and weather conditions. The guides position and operate the vessel during fishing with the use of electric trolling motors that allow them to move the boat in relative silence with little water disturbance. Fishermen generally follow the guidance of the guides regarding where to cast and at what distance from the margins to increase the likelihood of encountering and hooking fish. Each vessel fishes separately at different locations and for varying times depending on the guides efforts at optimizing productivity . In general, the fishing boats depart from the mobile floating hotel base prior to 7:00 hrs. and return between 16:00 and 17:00 hrs. On average each pair of fishermen fish for 8 hours a day, discounting any necessary transfer/travel time and a lunch break. All captured specimens are manipulated following a stress minimization protocol where the guide lands and then handles all fish caught with tools designed to minimize any injury to the fish (Boga-grip). The guide removes artificial lure hooks, enables quick photography of the angler with the specimen and confirms the specimen’s weight using the Boga-grip’s calibrated scale (see protocol attached – Appendix A). The fishermen handle the specimens only briefly for photography, upon which they are immediately returned to the water, resuscitated and released. No specimens are retained, except under the exceptional condition where the fish may qualify for a world record that requires the specimen be retained for proof or if for some reason the animal suffers injuries which the guide deems that it will not survive. The standard is capture and release of 100% of the captured specimens.

Data collection

During the entire period of operation of the fishing activity, data on environmental and hydrological parameters, fishing effort and daily catches were collected to generate a rapid environmental analysis for correlation to the fishing statistics generated.

Collection of Hydrological data – Water and environmental data were collected by an Acute Angling staff member trained as a field technician and consisted of basic water quality measures: electrical conductivity, dissolved oxygen, pH and water temperature. These measurements were taken using a YSI-calibrated multiparametric probe, model 555. Water transparency data were measured using a Secchi disc. In order to compare limnological conditions in the various fishing environments, the sampling of environmental data was stratified into 3 categories: river channel, lakes and ressacas. A total of 131 water quality samples from measurements between 26/Sep and 2/Nov 2019 were taken, divided between 58 river samples, 47 ressaca samples and 26 lake/lagoon samples (Figure 5).

In addition, 4 limnometric water level measuring stations were installed to record variation of water levels in fishing zones 1-3. These gauges were installed, geo-referenced and marked with gradations referenced to fixed positions established in the riverbank for each region. Thus, the values of variation of water level are absolute values of local variation without correlation between waters. This calibration is only possible with the establishment of level references using altimetry with geodesic GPS and either telemetry or datalogging. The information collected served to determine river level fluctuations during the period of operation of the fishing activity. Water level data were collected at irregular intervals, depending on the position of the Blackwater Adventurer floating hotel, and demonstrate changes in river level in relation to the previous reading in the same zone.

Figure 5. Location of hydrological sampling points and position of water level gauges.
Figure 5. Location of hydrological sampling points and position of water level gauges.

Collection of Fishing data - Fishing effort and catch data were recorded daily by the Acute Angling guides in each of the 4 fishing boats, utilizing a standardized form designed for this purpose. The recorded data include the number of specimens captured for each species and the phenotype in the case of Cichla temensis, to record the relationship between açu and paca, the 2 extremes of the naturally occurring cyclical color and pattern variation. The form used distinguished between groups divided into intervals of 5 pounds of weight as shown in the field form example in Figure 5. Specimens of peacock bass weighing more than 20 pounds were recorded individually. The catch sites were recorded as per the fishing areas demarcated in Figure 4. Fishing effort was measured in fishing hours/day/fisherman for each vessel, tabulated weekly for each fishing group and then expressed as combined catch effort for each group. The results are presented in terms of total catch numbers per week for each species and by size class for Cichla temensis, combining both açu and paca.

Figure 6. Example of the daily report form used by guides in the field.
Figure 6. Example of the daily report form used by guides in the field.

Analysis of data and results

Analysis of Hydrological parameters - The location of hydrological sampling points is shown in Figure 5, with the highest concentration of sampling points in fishing areas 1-3. The summary of the data is described in Table 1. Water temperature during the sampling period ranged from a minimum of 25.1 to 32.3 degrees centigrade, with a general average of 27.6 degrees. No significant differences in temperature were detected between the surface and bottom samples taken in the river channel although differences were detected between the 3 sampled environment types. (Figure 6). Electrical conductivity ranged from 17 to 36 micro Siemens with an average of 27.6, although ressacas and lakes showed a greater total variation when compared to river values. These values are within the expected range of variation for rivers in the Rio Negro basin, which have an extremely low concentration of ions in solution.

Dissolved oxygen showed varying mean values in the 3 different environments, with the river values being higher (with a minimum of 4.3 ml/l), while the minimum values for ressacas and lakes were 0.7 and 0.1 respectively for samples near the bottom, indicating hypoxia in some lake and ressaca environments with less water movement. The values found in the river are typical for the channel and represent a relatively high level of oxygenation. The occurrence of hypoxia in lakes and ressacas is also a normal event during the dry season when there is a higher localized oxygen demand due to the decomposition of organic matter derived from riverside vegetation, coinciding with less water circulation.

PH and water clarity (transparency) results are shown in Figure 7. pH was the parameter with the least variation observed among all samples. Values ranged between 3.0 and 4.5 with an average of 3.9, considered highly acidic anywhere else, but relatively normal for the black waters of the Rio Negro basin. Similarly, water transparency data show a variation between 0.8 and 1.9 meters, with an average of 1.1 meters, which, although darker and more heavily tannin-stained than most Rio Negro tributaries, is similar to several other rivers in the region. The set of these water quality data indicate that the environments sampled in the Rio Curicuriari River are all within the expected range of variation and there is no evidence of environmental change in the region.

Table 1. Summary of water quality data for the three monitored environment types.
    Water Temp Cond. mS. O.d. pH Transparency
  Average 27.6 25.3 5.3 3.9 1.1
River Max. 30.2 29.0 7.0 4.5 1.9
  Min. 26.1 17.0 4.3 3.7 0.8
  Average 27.7 26.1 4.5 3.9 1.1
Ressaca Max. 31.3 35.0 6.9 4.5 1.5
  Min. 25.1 17.0 0.7 3.0 1.0
  Average 27.6 25.0 3.6 4.0 1.1
Lake Max. 32.3 36.0 6.8 4.5 1.9
  Min. 25.1 17.0 0.1 3.7 0.9
  Average 27.6 25.5 4.5 3.9 1.1
General Max. 32.3 36.0 7.0 4.5 1.9
  Min. 25.1 17.0 0.1 3.0 0.8
Figure 7. Temperature, conductivity and dissolved oxygen data stratified by environment type.
Figure 7. Temperature, conductivity and dissolved oxygen data stratified by environment type.
Figure 7. PH and water transparency data stratified by fishing environments.
Figure 7. PH and water transparency data stratified by fishing environments.

The water level data of the most centrally located gauge are presented in Figure 8. The level of the Rio Curicuriari was in the accelerated ebb phase between the last week of September and the beginning of October reaching a minimum level during the period of operation on October 3rd, rising again between October 10th – 15th, after it rained heavily for nearly a week. Water levels continued to oscillate up and down until the end of the period of operation. The total amplitude of water level variation during the measurement period was 78 cm (less than 3 feet). The data do not permit the generation of a time series that would allow creation of a river-wide hydrograph, due to the fact that the operation’s movement required collecting data from each of the gauges at different times. The gauge data were, however, useful to the field team to determine whether the river had descended or risen between consecutive observation periods and thus in which direction to move to optimize productivity.

Figure 8.  Hydrograph of Rio Curicuriari water level oscillations during the 2019 fishing season.
Figure 8. Hydrograph of Rio Curicuriari water level oscillations during the 2019 fishing season, showing variations of up to 78 cm (less than 3 feet) in either direction during the region’s dry season.

Results of Fishing Data

The results of fish catch by species and weight group for Cichla temensis and Cichla orinocensis are presented below, both graphically and in tabular form. The data were organized in daily and weekly catch summaries for the 6 weeks of operation of the sport fishing activity. The daily and total capture data by weight group are shown in Table 2, Graph 1 and Figure 9.

Table 2. Summary of daily catches of exemplars of both fished species.
Size groups <2 2-5 5-10 10-15 15-20 >20 Total temensis. Total orinocensis Total catch
Total catch 27.0 23.0 27.0 17.0 19.0 49.0 162.0 1584.0 1746.0
Daily minimum 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.0 5.0
Daily average 0.7 0.6 0.7 0.4 0.5 1.3 4.2 40.6 44.8
Daily maximum 4.0 4.0 6.0 4.0 3.0 4.0 14.0 92.0 94.0
Graph 1. Analysis of percentage of Cichla temensis per size grouping – in lbs.
Graph 1. Analysis of percentage of Cichla temensis per size grouping – in lbs.

A total of 39 days of fishing occurred with a total fishing effort of 1924 hours and a total catch of 1746 specimens, with a catch per unit of effort (CPUE) of 0.9 catches per hour of fishing. The average daily catch is 44 specimens, ranging from 5 minimum to 94 maximum. C. orinocensis accounted for 90.7 % of the catches, while C. temensis accounted for 9.3 % of the specimens. Among the weight groups for C. temensis, the group weighing over 20 pounds was the largest group, representing 30% of the captured specimens. The other size groups had captures ranging from 10 to 17 %.

The data show that the most immediately visible differentiating characteristics of the Rio Curicuriari system are; (1) the low number of total fish caught, (2) the surprisingly low total number of Cichla temensis and (3) the extraordinarily high percentage of C. temensis caught that weigh over 20 pounds. Decades of catch records for Rio Negro basin fisheries generally show a percentage of <1% of all fish caught for specimens in the 20 pound size class. Total catch numbers in Rio Negro basin fisheries, however, generally total 3 times higher than what was recorded here, tempering the percentage differences and suggesting that the likelihood of encountering fish over 20 pounds is roughly 10 times higher in the Rio Curicuriari than the Rio Negro basin in general.

Weekly catches per fishing group show that the week of fishing, between September 30th and October 6th was the most productive in terms of catches, with a total of 164 specimens caught while the following week showed the lowest productivity with a total of 46 specimens caught (Figure 10). However, normalizing the catches per unit of effort, shows that week 5 (October 21st – 27th) was actually the most productive considering the number of hours fished. (figure 11). Week 2 showed the largest capture of specimens weighing more than 20 pounds, with a total of 14 specimens in this weight class (figure 12), and one specimen of 27 pounds, within 2 pounds of the world record. There were specimens above 20 pounds captured in all weeks of fishing with the exception of week 3. It is noteworthy that catches of small individuals in the first 2 size classes accounted for between 16 and 21% of the total catches in the first 2 weeks of fishing and subsequently increased to between 20 and 60% in the following weeks. Specimens of classes over 15 pounds ranged from 20 to 50% in number of catches, with 3 weeks where values were around 50%. This balanced distribution of catches with a high number of large specimens is an indication that the C. temensis population is stable and shows no evidence of significant fishing pressure. It is apparent that fishing effort in general was focused on capturing larger specimens, which is to be expected in a sport fishery. Anglers tend to specifically seek the capture of "trophies". The guides are experienced in reading the conditions of the river to determine the areas most likely to provide large fish, so that fishing is not spatially random.

Figure 9. Daily catches of C. temensis (in both açu and paca form), combined by size class.
Figure 9. Daily catches of C. temensis (in both açu and paca form), combined by size class.

The homogeneous distribution of catches per unit of effort indicates that there was no fishing saturation and there was no decrease in fishing yield over the period of operation (Figure 11). If there were saturation or a decrease in productivity, it would be reflected in the total catch numbers and a decline in CPUE over the fishing period. Variations from week to week are probably associated with a combination of fishermen's effort and ability and the constant oscillations in water level and temperature that inhibits or encourages fish to attack artificial baits. It is recognized that during periods of ebbs the catches tend to be higher because the fish leave the igapó and concentrate in the river channel where the presence of prey increases during the period of low waters. Upward water level oscillations tend be associated with a drop in water temperature and greater access to floodplain vegetation. The Curicuriari experienced oscillations in both directions during the fishing period, which occurred during the river’s overall low water period. These results confirm that there was no overfishing during the period of operation and that the fishing effort expended is well within the limits of fishing sustainability. These results further reflect the effectiveness of the strategy of rotation of fishing areas and the dilution of fishing effort by utilizing an extensive area throughout the fishery.

Figure 10. Result of weekly catches in number per species.
Figure 10. Result of weekly catches in number per species.
Figure 11. Catches per fishing effort unit, represented by number of specimens caught per hours of fishing per week.
Figure 11. Catches per fishing effort unit, represented by number of specimens caught per hours of fishing per week.
Figure 12. Weekly captures - results per weight group for C. temensis.
Figure 12. Weekly captures - results per weight group for C. temensis.

Sustainability - The variability of catches per week is associated with the broad range of variable day-to-day parameters occurring naturally within the river’s 4-month dry season and the range of fishing characteristics employed. The variables include; angler effort, angler skill, ambient weather conditions, water temperature and the direction of variation of the river’s in-season water level oscillations. Although water levels are at their lowest on a macro-scale during the river’s dry season, monitoring of water level during the fishing period showed constant daily up and down variations due to periods of rainfall and subsequent dry periods; with ebb conditions generally being the most productive. Due to the large extent of the fishing area and the often localized effects of the river's rainfall and drainage response pattern, the fishing operation is constantly prepared to move to find optimal fishing conditions. Thus, the rotation of fishing areas is not only necessary for maintaining fishing efficiency, but at the same time serves to dilute pressure over any one specific area. This constant mobility strategy permits one or two areas to be fished in a week, leaving these areas at rest for two or three weeks thereafter. This strategy allows for an area and any previously caught specimens to recover.

This level of sustainable operation is only possible with careful control over fishing activity and with a low fishing intensity such as reported here. It is essential that any sport fishing activity in this region be performed in the manner implemented by this operation and that it does not exceed a maximum limit of fishermen per week. This study demonstrated that groups of 8 fishermen per week delineate an adequate and safe level to ensure that there is no harm to the population of the target species or the fishery. The results generated by the data corroborate the objectives defined by the fishing operation for sustainable exploitation of sport fishing in the Rio Curicuriari.

Appendix 1 – Fish Handling Protocol

In order to ensure consistent safe handling and minimize mortality, the following fish handling protocol is applied in the Rio Curicuriari fishery, as in all Acute Angling fishing operations;

  1. Responsibility for fish handling.
    1. The guide is responsible for all fish handling, not the angler.
    2. Only properly trained guides may assist clients fishing
    3. The guide may not permit the angler to mishandle captured fish.
  2. Minimizing fish stress during capture.
    1. The guide should be aware of the time and effort being expended by a hooked fish and ensure that he acts to minimize this effort;
      1. By moving the boat, following the captive fish as necessary, to shorten fighting time and distance from capture.
      2. To use rotational boat positioning to assist anglers in maintaining the most efficient vector to shorten fighting time and avoid entanglement in the igapó.
    2. Guides must ensure that the equipment provide by Acute Angling, which is designed to allow quick capture, is used in the configuration provided, without permitting gross effectiveness-diminishing modifications by anglers.
  3. Landing the fish.
    1. Whenever possible, a boga-grip tool should be used to complete capture of the fish. Once safely immobilized by the Boga-grip, the guide will remove hooks to complete the successful landing of the fish.
    2. If necessary, due to frayed line, bent hooks or other issues risking incomplete landing, the guide may use the landing net.
      1. If the net is used, a boga-grip should be employed to remove fish from the net, not hands.
      2. The fish should be unhooked as per boga-grip instructions
    3. Clients may not be involved in mechanically landing the fish.
  4. Handling a landed fish
    1. The fish must remain on the boga-grip at all times.
    2. The client may hold the fish, via the boga-grip, and a supporting hand on the fish’s ventral side, if necessary, while photographs are taken.
      1. 30 seconds is the maximum time for photography
      2. Fish may not be placed on any surfaces for photography (other than an IGFA supplied and approved measuring device if a fish is a candidate for a record).
      3. Clients m ay not insert hands into gills, hold fish without a boga-grip or suspend fish by the tail.
    3. Guides must take action to protect the fish if the angler is extending the 30 second limit or mishandling the fish.
  5. Releasing the fish.
    1. Fish should always be released in a safe area, near structure, to minimize the possibility of predation.
    2. The fish should be returned to the water and submerged with the boga-grip
    3. If the guide judges the fish is not overly tired, it should be released gently from the boga-grip.
    4. The guide may determine that resuscitation is necessary, based on the fish’s behavior and time expended. If resuscitation is necessary;
      1. Fish must be held in the water by the boga-grip and moved in a figure-8 fashion to help reoxygenate the blood via the gills, either by the guide or by the angler with guidance from the guide.
      2. The boat may also used to slowly move the fish forward through the water.
      3. The fish should not be moved in a back and forth motion, which diminishes the value of resuscitation efforts.
    5. Although dolphin are present in some areas in the Curicuriari, they have not learned that fishing boats represent opportunities to prey on tired fish. The fishing operation will use all possible efforts make certain to not create the opportunity for that behavior to be learned. Guides must use exceptional caution when releasing a fish with a dolphin in the area.

If clients are not obeying the directions of a guide and are posing a threat to the safety of captured fish, the guide must report this to his manager. The manager must explain, in English and in a polite fashion, that our contract with the tribe and our licensure by the government dictates that no angler will be permitted to fish in this operation if these fish handling protocols are not followed and if fish are being endangered.