Monthly Archives: December 2015
Maintaining good water quality is essential to maintaining the health of our harbor. Water quality refers to the condition of water relative to legal standards, social expectations or ecological health. In order to track water quality conditions in the harbor and identify specific areas of concern, long term water quality monitoring is a must.
A number of organizations conduct water quality monitoring water quality in Charlotte Harbor and its adjacent tributaries. What follows is a look at some of the organizations who conduct water quality monitoring and the reasons why:
FDEP, Charlotte Harbor Aquatic Preserves Volunteers – Conduct monthly sunrise sampling at 40+ fixed locations from Lemon Bay to Estero Bay. Initiated in 1996, trained volunteers sample mostly near shore shallow waters. Sunrise sampling serves to identify Dissolved Oxygen levels (necessary for plant & animal survival) at their lowest levels.
Fisheries management is complicated as many anglers know. Since scientist have no way of counting all of the fish in the Gulf, or in a given estuary, they have to do stock assessments based on their best estimate of how many fish are removed and how many fish are recruited into the system. This involves not only figuring out how many fish anglers harvest but also how many die naturally (old age, predation, etc.). It also involves knowing at what size a fish spawns, how often a fish spawns, and how many eggs are spawned. And then of course things get really complicated like knowing whether all fish of a same species spawn equally, or how habitat, tides, and currents affects spawning and recruitment. And what about things like red tide events? At the end of the day the more scientist can learn about all of these things the better they are able to accurately describe stocks for management purposes.
To that end the Florida Fish and Wildlife Conservation Commission’s-Fish and Wildlife Research Institute (FWRI) recently published findings on three of our favorite species: snook, redfish, and spotted seatrout. The findings are the result of three separate studies conducted in the Tampa Bay area and designed to capture important information about spawning behavior.
Good anglers know that to catch fish you must think like a fish; know where they’re hanging and what they’re eating. Although redfish, snook, and many other predator fish are opportunistic in their feeding habits, they do key into specific prey items based on what’s available in their desired size range, and this varies geographically and seasonally.
One of the best studied fish in Charlotte Harbor is the common snook. Since 1989 the Florida Fish and Wildlife Conservation Commission’s-Fish and Wildlife Research Institute (FWRI) has conducted research and monitoring of our local fisheries out of a lab in Murdock. In one study that they conducted over a two year period, stomach contents of almost 700 snook 12-35 inches were evaluated to determine feeding habits based on size, season, and location. They found prey in over half of the stomachs; 37 different prey species were recorded and of them 71% were fish. Pinfish (20%), anchovy (16%), and pink shrimp (13%) made up almost 50% of the common snook diet.
Interestingly, snook eat greater than 10 times more pinfish in the summer months than in the winter even though pinfish are more abundant in the winter months. The reason for this has everything to do with size. Young of the year pinfish recruit to the estuary in the winter and are abundant but very small. They grow fast and by summer are much larger but are less abundant. FWRI’s research showed that even though pinfish are less abundant in the summer, they are the preferred size. Even more interesting is that both pinfish and anchovy found in the stomachs of small snook over the course of the study were significantly larger than the average size of those same species collected in the estuary using a seine net. What this tells us is that snook are cuing into a specific size pinfish even though that size is not what’s most abundant. This study found a significant predator size/prey size relationship between common snook and fish prey. Snook seem to cue into prey that averages 14% of their own body length. In contract, FWRI found no significant difference in pink shrimp size noted between that found in snook stomachs and that found in the estuary. Snook feed on pink shrimp consistently each season with the highest rate of consumption in the winter. Pink shrimp size only varies slightly among the different seasons in the estuary but abundance is variable.