Introduction
In sport fishing, many factors influence the success of an outing: water temperature, currents, presence of prey… but one indicator is still too often overlooked: Chlorophyll concentration. A product of phytoplankton activity, Chlorophyll is a precious biological marker for identifying areas of high marine productivity – those where fish feed, move… and sometimes allow themselves to be captured.
Today, it can be measured from space thanks to satellites, giving fishermen access to reliable, up-to-date data on vast marine areas.
In this article, you’ll discover why Chlorophyll is a real asset when it comes to spotting good fishing spots. We’ll also explain how it interacts with water temperature, currents and even sea level (SSH) – all valuable clues to better understand where fish are hiding!
Display Chlorophyll in TZ iBoat
To find the ideal fishing areas based on Chlorophyll, here’s how to activate the Chlorophyll data display in TZ iBoat. Start by activating the SportFishing Ocean-O layer to display the data.
Next, activate the Chlorophyll layer to display the Chlorophyll concentration as a Color line.
Definition and importance of Chlorophyll
Chlorophyll, a photosynthetic pigment present in phytoplankton, gives it a green hue visible at the surface, making it possible to estimate its concentration and, by extension, the quantity of phytoplankton in the marine environment. Chlorophyll production takes place over several days, depending on environmental conditions such as light, temperature and nutrients. Once present, chlorophyll is transported by horizontal currents, influencing its distribution on the ocean surface. This data is particularly valuable, as it provides a direct indication of biological activity at sea, which other physical or chemical parameters alone do not allow. It thus complements oceanographic observations by providing an essential insight into marine productivity and ecosystem dynamics.
Chlorophyll’s role in the food chain
Chlorophyll plays a fundamental role in the marine food chain, enabling phytoplankton to capture light energy for photosynthesis. Chlorophyll-rich phytoplankton are consumed by zooplankton, which in turn are eaten by larger organisms such as fish, marine mammals and birds. In this way, Chlorophyll is indirectly responsible for the energy that circulates through all trophic levels of marine ecosystems.
Light penetrates to depths of around 200 meters: this is the zone corresponding to the habitat of species targeted by pelagic fishing.
The importance of chlorophyll fronts
A chlorophyll front is a clear transition zone between water masses with different biological and physical characteristics, notably between clear, nutrient-poor waters and turbid, phytoplankton-rich waters. These zones are ecologically rich, favoring high biological productivity that attracts numerous marine species, creating biodiversity “hotspots”. They are visible from satellites thanks to their chlorophyll concentration and vary with the seasons and currents. For fish, these fronts act as natural barriers where they accumulate, making them important fishing grounds.
Interpretation of Chlorophyll levels
Low Chlorophyll concentration (<0.1 mg/m3)
These waters are very clear, generally low in nutrients, and harbor little marine life, making them unsuitable for fishing due to their low biological productivity.
Moderate Chlorophyll concentration (0.1-2 mg/m3)
These waters offer a balance between clarity and the presence of phytoplankton and are ideal for fishing, as they favor both visibility and high marine productivity, attracting numerous species.
High Chlorophyll concentration (between 2 and 10 mg/m3)
These waters are rich in phytoplankton but are too turbid and lose transparency, limiting visibility and living conditions for certain species, making them much less favorable for fishing.
Very high chlorophyll concentration (>10 mg/m3)
These waters are too rich in phytoplankton and are often very turbid and oxygen depleted. These waters create unfavorable conditions for marine life, making them unsuitable for fishing.
The best places to find fish are at the interfaces between areas rich in chlorophyll (food supply) and areas poor in chlorophyll (clear, oxygenated water).
Chlorophyll and other data
Chlorophyll and SST (Surface Temperature)
There’s a close relationship between sea surface temperature (SST) and Chlorophyll concentration: cold waters are generally richer in nutrients, as they often originate from nutrient-laden deep-water upwellings. This richness favors the growth of phytoplankton, which contain Chlorophyll, resulting in high biological productivity in these areas.
Chlorophyll and Ocean Currents
The convergence zones of ocean currents are often rich in phytoplankton, as they concentrate the nutrients necessary for their growth, creating areas of high productivity. In addition, ocean eddies can trap chlorophyll at the surface and maintain local conditions favorable to marine life, creating dynamic ecosystems attractive to many species of fish.
Chlorophyll and SSH (Altimetry)
A low sea surface height (SSH) is often associated with a high concentration of Chlorophyll, as it indicates the presence of upwellings, upwellings of cold, deep water towards the surface. These deep waters are rich in nutrients, stimulating phytoplankton growth and leading to high Chlorophyll production, thus favoring the development of marine life in these areas.
The transitions between high and low SSH zones identify the areas where phytoplankton development is greatest.
Case study in TZ iBoat
With TZ iBoat, here’s a simple and effective way to read chlorophyll data and spot the most interesting areas for fishing.
To properly analyze chlorophyll concentration, it’s essential to use an appropriate color palette, set manually on a scale from 0.01 to around 2 mg/m³, and even up to 6 mg/m³. This palette enables you to clearly visualize the areas of interest, distinguishing between very clear water (in blue), more productive areas (in green) and overly turbid areas (in dark green or yellow).
Next, we need to identify chlorophyll fronts, visible thanks to the narrow isolines. These fronts mark clear transitions between waters rich and poor in phytoplankton and are biologically active zones. They are particularly important for fishing, as they limit the movement of fish between clear waters, where they feed, and richer waters that are less favorable from a visual or respiratory point of view.
It is also important to observe the absolute chlorophyll value. A concentration of between 0.1 and 1.5 mg/m³ is generally optimal for fishing: it reflects a good balance between water clarity and productivity. Below 0.1, the water is too low in nutrients, and above 2 mg/m³, it becomes too turbid, sometimes low in oxygen, making it less suitable for marine life.
To refine the analysis, Chlorophyll can be cross-referenced with other data such as surface temperature (SST) or sea surface height (SSH). For example, low SSH often indicates the presence of upwellings, which bring nutrients and increase chlorophyll concentration. Finally, it is useful to consider underwater topography, such as continental shelves or drop-offs, which strongly influence phytoplankton distribution.
Thus, a good chlorophyll reading relies on the combined analysis of gradients, absolute values and surrounding physical conditions, to identify the most favorable fishing areas.
The example below illustrates these steps:
Conclusion
Long relegated to second place in marine data analysis, chlorophyll is now a key indicator for sport fishermen. Thanks to satellite images and their integration into tools such as TZ iBoat, it is now possible to pinpoint areas of high marine productivity – veritable fish magnets. By cross-referencing Chlorophyll data with surface temperature, ocean currents and sea level, we can gain a detailed understanding of undersea ecosystems – and hence a more effective fishing strategy.
A better understanding of marine life also means better fishing: Chlorophyll then becomes much more than a simple layer; it’s a real key to reading the ocean.
In our next article, we’ll look at the analysis of ocean currents, another decisive factor in fine-tuning your fishing strategies.